**1. Introduction**

In recent years, genetic studies on dog genomics have multiplied worldwide. Currently, there are over 50 international laboratories which are involved in canine genome projects and several applications will be available in the near future from these studies. These new findings will improve our understanding of the selection process of the dogs and provide useful information for the study and control of genetic diseases.

### **2. Basic genetics**

The single-control characters are influenced by genes located in a locus on one of the pairs of the chromosomes (78 in the dog) and have a binomial distribution. For example, the hair length in dogs is coded by two genes present at an autosomal locus. Short-haired animals have genotype LL (dominant homozygotes), while, long-haired animals have genotype ll (recessive homozygotes). From their mating originates short-haired animals with genotype Ll (heterozygotes), indistinguishable from short-haired parents. Even those characters that express different degrees of dominance, different from the Mendelian inheritance, are considered simple characters (e.g. incomplete or partial dominance). The simple characters are not influenced by the environment and, therefore, to each genotype corresponds a certain phenotype (P = G, where P = phenotype and G = genotype). The study of simple characters includes also multiple alleles (several alleles present in a population), pleitropy, association or linkage and incomplete penetrance. For characters

with simple inheritance, it is easier to make selection than for multiple control characters. The multiple control characters are also called quantitative or polygenic characters. These characters are influenced by many genes distributed on several loci and they are influenced by environmental factors. The strong artificial selection exercised by man during the domestication process and during the creation of the different breeds has led to the setting of several characters. Color inheritance illustrates the case of separate loci that control the expression of the phenotype. The coat of dogs consists of two parts: top coat (protective function) and undercoat (heat-insulating function). Some breeds have no undercoat (e.g. Yorkshire). The color of the coat depends on the characteristics of the pigments contained in the medullary and cortical layers of the hair [1]. According to Willis [1], it is possible to explain all the colors by means of two chemical pigments: hemoglobin and melanin. More specifically, melanin is differentiated into eumelanin (black-brown) and pheomelanin (yellow-reddish). The synthesis of pigments in the hair of mammals depends on the interaction between the Agouti protein and the Melanocortin 1 receptor [2]. The coat colors in the dog are linked to the presence/absence of two types of melanin and their possible combinations. It is important to underline that melanin do not show a precise time of formation and they develop during the different phases of the fetal development and after birth [1]. The knowledge of the genetic inheritance of the morphological traits is very important in order to establish suitable selection objectives in the different breeds.

#### **3. Relationship and inbreeding**

Measurement of F coefficient (consanguinity) in a population can be considered as a measure of the increase in the proportion of homozygous individuals following an inbreeding mating (between relatives) [3]. The coefficient of consanguinity F can be calculated with the following methods: 1) pedigree 2) run of homozigosity (ROH); 3) genomic kinship matrix; 4) SNP genotyping [4, 5]. Inbreeding can occur in small closed populations due to mating between related animals. In a closed population, the decrease in the fraction of heterozygotes from one generation to the next may be referred to as ΔF. This value varies in relation to the size of the population: ΔF = 1 / 2Ne where Ne is the effective number or effective size of the population. In a population, Ne depends on the number of males (Nm), and on the number of females (Nf), in the following relationship:

$$\mathbf{1}/N\mathbf{e} = \mathbf{1}/4\mathbf{N}\mathbf{f} + \mathbf{1}/4\ \mathbf{N}m; \Delta F = \mathbf{1}/8\mathbf{N}\mathbf{f} + \mathbf{1}/8\ \mathbf{N}m\tag{1}$$

The inbreeding coefficient, at a given t generation, can be calculated as a function of ΔF and t as:

$$\mathbf{F}\_{\mathbf{t}} = \mathbf{1} - \left(\mathbf{1} - \Delta F\right)^{\mathbf{t}} \tag{2}$$

**5**

*Canine Genetics and Genomics*

*DOI: http://dx.doi.org/10.5772/intechopen.95781*

an optimal genetic diversity in the population.

The general actions to be taken in a program for the genetic improvement within a breed should include: 1) genomic identification and characterization of individuals, highlighting their potential in terms of their contribution to maintaining biodiversity, aptitude and use 2) monitoring of demographic parameters and assessment of the risk of reduced genetic variability 3) characterization and evaluation of the intra-breed genetic variability for proper management activities. Modern molecular techniques can be helpful for the improvement of management strategies, even for small breeds and for qualitative traits. The current hypothesis is to add molecular data to classical schemes (assisted selection) to improve their accuracy. The first step in planning an improvement program consists of: 1) a clear definition of the objectives 2) identification of the traits to be recorded 3) evaluation of the gene effect of the characters to be selected 4) estimate of the effect of the environment

**4. Breeding programs and strategies**

resistance to diseases, longevity, etc.). These findings are based on the results of experiments carried out on different breeds and for several generations. Leroy *et al.* [8] showed that the increase in inbreeding in the population has an effect on individual survival and litter size of different breeds. Deleterious effects begin to occur when the value of F is about 0.375. Lower values are not to be considered dangerous. It is worth noting that this is the level of inbreeding that is achieved in only two generations of full sibling mating. For this reason, it is recommended to avoid mating between close relatives. Consanguinity is influenced by the number of individuals used per generation [9]. As a general rule, individuals whose numbers are lower in the breeding population they exert a proportionately greater effect on consanguinity. This is true both in relation to the male/female ratio (depend more on the number of males) and the different numbers of breeders in the various generations. The actual number of breeding animals is the parameter used in small populations to determine the expected inbreeding coefficient. Since the less numerous sex is the most important, the actual number of the population can be calculated even if the number of the larger sex is not known (e.g. 2 males and the number of females is assumed to be infinite: 1/Ne = 1/ 4Nf = 1/4 (2) =1/8 \* F = 1/16 = 0.0625). The family size is the number of offspring in each family who become parents in the next generation. In ideal conditions, the size of the population will remain constant in subsequent generations if each parent is replaced by another individual. In this case, the average number of offspring per parent is equal to 1 with an average family size of 2 (two parents). The Ne is also function of the variance of the family size. If males mate with more than one female, the number of offspring and thus the variance of the family size will differ between the two sexes. Several measures can be implemented to keep consanguinity within acceptable limits in the population: increase the number of breeders; mating of one male with a female (since the number within the sexes is the same, Ne will be maximized), reduce the variance size of the family (for a constant number of offspring for each family, the variance is equal to 0 and the Ne is double); avoid mating between siblings or cousins; avoid mating individuals in generations that overlap as inbreeding increases. If the management program includes the genetic improvement of one or more characters, selection must be carried out using selection indices that take into account of the level of relationship. The goal is to find the optimal number of offspring for each breeding animal and determine if a young animal (a candidate for selection) should be selected for breeding or not. This is done in an optimal way using the software EVA [10] that guarantees the achievement of the genetic progress and the maintenance

which shows the decrease (ΔF) of heterozygotes that occurs at each generation following inbreeding [6]. Lewis *et al.* [7] reported for 221 breeds of the UK Kennel Club a Ne that varies between 23.8 of the Manchester terrier breed to 918 of the Borzoi breed and an average value of F equal to 0.06. The deleterious effects of inbreeding are universally known. They can be summarized briefly in the increase in the frequency of all genetic defects and abnormalities (reproductive sphere,

#### *Canine Genetics and Genomics DOI: http://dx.doi.org/10.5772/intechopen.95781*

*Canine Genetics, Health and Medicine*

with simple inheritance, it is easier to make selection than for multiple control characters. The multiple control characters are also called quantitative or polygenic characters. These characters are influenced by many genes distributed on several loci and they are influenced by environmental factors. The strong artificial selection exercised by man during the domestication process and during the creation of the different breeds has led to the setting of several characters. Color inheritance illustrates the case of separate loci that control the expression of the phenotype. The coat of dogs consists of two parts: top coat (protective function) and undercoat (heat-insulating function). Some breeds have no undercoat (e.g. Yorkshire). The color of the coat depends on the characteristics of the pigments contained in the medullary and cortical layers of the hair [1]. According to Willis [1], it is possible to explain all the colors by means of two chemical pigments: hemoglobin and melanin. More specifically, melanin is differentiated into eumelanin (black-brown) and pheomelanin (yellow-reddish). The synthesis of pigments in the hair of mammals depends on the interaction between the Agouti protein and the Melanocortin 1 receptor [2]. The coat colors in the dog are linked to the presence/absence of two types of melanin and their possible combinations. It is important to underline that melanin do not show a precise time of formation and they develop during the different phases of the fetal development and after birth [1]. The knowledge of the genetic inheritance of the morphological traits is very important in order to estab-

Measurement of F coefficient (consanguinity) in a population can be considered as a measure of the increase in the proportion of homozygous individuals following an inbreeding mating (between relatives) [3]. The coefficient of consanguinity F can be calculated with the following methods: 1) pedigree 2) run of homozigosity (ROH); 3) genomic kinship matrix; 4) SNP genotyping [4, 5]. Inbreeding can occur in small closed populations due to mating between related animals. In a closed population, the decrease in the fraction of heterozygotes from one generation to the next may be referred to as ΔF. This value varies in relation to the size of the population: ΔF = 1 / 2Ne where Ne is the effective number or effective size of the population. In a population, Ne depends on the number of males (Nm), and on

1 / 1 / 4Nf 1 / 4 ; 1 /8Nf 1 /8 *Ne* = + ∆= + *Nm F Nm* (1)

F11 t = − −∆*F* (2)

The inbreeding coefficient, at a given t generation, can be calculated as a func-

( ) t

which shows the decrease (ΔF) of heterozygotes that occurs at each generation following inbreeding [6]. Lewis *et al.* [7] reported for 221 breeds of the UK Kennel Club a Ne that varies between 23.8 of the Manchester terrier breed to 918 of the Borzoi breed and an average value of F equal to 0.06. The deleterious effects of inbreeding are universally known. They can be summarized briefly in the increase in the frequency of all genetic defects and abnormalities (reproductive sphere,

lish suitable selection objectives in the different breeds.

the number of females (Nf), in the following relationship:

**3. Relationship and inbreeding**

**4**

tion of ΔF and t as:

resistance to diseases, longevity, etc.). These findings are based on the results of experiments carried out on different breeds and for several generations. Leroy *et al.* [8] showed that the increase in inbreeding in the population has an effect on individual survival and litter size of different breeds. Deleterious effects begin to occur when the value of F is about 0.375. Lower values are not to be considered dangerous. It is worth noting that this is the level of inbreeding that is achieved in only two generations of full sibling mating. For this reason, it is recommended to avoid mating between close relatives. Consanguinity is influenced by the number of individuals used per generation [9]. As a general rule, individuals whose numbers are lower in the breeding population they exert a proportionately greater effect on consanguinity. This is true both in relation to the male/female ratio (depend more on the number of males) and the different numbers of breeders in the various generations. The actual number of breeding animals is the parameter used in small populations to determine the expected inbreeding coefficient. Since the less numerous sex is the most important, the actual number of the population can be calculated even if the number of the larger sex is not known (e.g. 2 males and the number of females is assumed to be infinite: 1/Ne = 1/ 4Nf = 1/4 (2) =1/8 \* F = 1/16 = 0.0625). The family size is the number of offspring in each family who become parents in the next generation. In ideal conditions, the size of the population will remain constant in subsequent generations if each parent is replaced by another individual. In this case, the average number of offspring per parent is equal to 1 with an average family size of 2 (two parents). The Ne is also function of the variance of the family size. If males mate with more than one female, the number of offspring and thus the variance of the family size will differ between the two sexes. Several measures can be implemented to keep consanguinity within acceptable limits in the population: increase the number of breeders; mating of one male with a female (since the number within the sexes is the same, Ne will be maximized), reduce the variance size of the family (for a constant number of offspring for each family, the variance is equal to 0 and the Ne is double); avoid mating between siblings or cousins; avoid mating individuals in generations that overlap as inbreeding increases. If the management program includes the genetic improvement of one or more characters, selection must be carried out using selection indices that take into account of the level of relationship. The goal is to find the optimal number of offspring for each breeding animal and determine if a young animal (a candidate for selection) should be selected for breeding or not. This is done in an optimal way using the software EVA [10] that guarantees the achievement of the genetic progress and the maintenance an optimal genetic diversity in the population.


**4.5 Goldenhar's syndrome (GS)**

*Special Considerations in Human Airway Management*

dysfunction and mouth opening limitation. TCS is associated with Cleft Palate in 30% of the cases, and pharyngeal hypoplasia is commonly associated as well. All these anomalies can disrupt several functions like breathing, swallowing, chewing, and speech. Systemic manifestations, namely cardiac, renal, and skeletal, especially

*Treacher Collins syndrome with characteristic facial features including downward and laterally slanting palpebral fissures, paucity of lashes and lack of naso-frontal angle, bird like appearance, micrognathia,*

*Airway and anesthetic implications*: Treacher Collins syndrome (TCS) was firstly reported as a hazard for general anesthesia in 1963 by Edward Ross due to the difficulty in maintaining a free and adequate airway. Several associated mechanisms are the cause, namely mandibular hypoplasia, micrognathia, retrognathia, posterior displacement of the bulky tongue, and the pharyngeal hypoplasia, resulting in a small and narrow retromandibular space [29, 30]. The presence of a temporomandibular joint abnormality or a small mouth aperture may further worsen the case. Thus, upper airway obstruction is common at induction of anesthesia and may require an airway manual maneuver (a two-hand mask ventilation, chin lift, and jaw thrust) and insertion of an oropharyngeal/nasopharyngeal airway. If unsuccessful, insertion of a supraglottic airway device such as a laryngeal mask airway before intubation is indicated. In addition, the failure rate of direct intubation is extremely high owing to the difficulty in alignment of the three axes (oral, pharyngeal, and laryngeal axes), which complicates further the visualization of the glottis. The degree of severity worsens with increasing age mainly because of the decreased

cervical vertebral defects, may also be observed [1, 4, 6, 7, 17].

*microtia (deformed pinna), macrostomia, and large tongue [27].*

**166**

**Figure 4.**

mandibular growth.

*Overview*: Goldenhar's syndrome, also called Facio-auriculo-vertebral syndrome or Oculo-Auriculo-Vertebral syndrome, is a variant of hemifacial microsomia disorders that affect the eye, ear, nose, lip, soft palate, and mandible, and often associated with vertebral and cardiac anomalies. It was initially reported in 1952 by a Belgian-American ophthalmologist Maurice Goldenhar. In 1963, Gorlin introduced the term "Oculo-Auriculo-Vertebral syndrome" due to the presence of associated vertebral anomalies (**Figure 5**).

*Genetics*: the exact etiology remains unclear. Most cases are sporadic, but some rare familial cases were reported suggesting autosomal dominant or recessive inheritance [33].

*Incidence*: Goldenhar's syndrome occurs in about 1 in 3000 to 1 in 5000 live births, affecting males predominantly. Male to female ratio is 2:1.

*Pathophysiology*: this hemifacial microsomia is caused by the underdevelopment of the first and second branchial arches during the 4th week of gestation resulting in craniofacial anomalies, ocular anomalies, vertebral anomalies, and cardiac defects.

*Clinical considerations*: Goldenhar's syndrome (GS) is a multisystem syndrome with a wide spectrum of clinical features. Craniofacial anomalies are unilateral in 90% of the cases and include mandibular hypoplasia, hypoplastic zygomatic arch, micrognathia, macrostomia, external and middle ear malformations (microtia, preauricular appendages, and atresia) often with sensorineural hearing loss, and eye anomalies (epibulbar dermoids, lipodermoids, microphthalmos, and coloboma). Nevertheless, in 10% of cases both facial sides may be affected with one side typically more affected than the other. Oral cavity anomalies like palate anomalies

#### **Figure 5.**

*Goldenhar's syndrome before and after surgical procedure for lip and palatoplasty, correction of macrostomia and nasal septum deformity, excision of pre-auricular tags: (A) preoperative; (B) postoperative [32].*

(high arch or cleft) and tongue anomalies are often associated. Additionally, almost 50% of children with Goldenhar's syndrome may have vertebral defects, especially at the cervical level, such as hemivertebrae or hypoplasia, along with a potential risk of subluxation at the atlanto-occipital joint. Neck movements are limited during flexion and extension, increasing the rate of difficult or failed tracheal intubation procedure. Congenital cardiac structural malformations (Tetralogy of Fallot and septal defects) are present in about one third of the cases. In rare cases, some degrees of mental retardation and other systemic anomalies, mainly genitourinary, pulmonary, and vascular are reported [4, 6, 7, 17].

*Airway and anesthetic implications*: anesthesia or sedation may be provided for children with Goldenhar's syndrome for various procedures (ear reconstruction, distraction osteogenesis, soft tissue reconstruction, skin graft, cardiac, etc.).

The anesthetic management is risky because of the difficult airway. The degree of difficulties depends directly on the severity of craniofacial anomalies and associated vertebral defects and tends to worsen progressively with increasing age. Detecting patients at risk in the preoperative setting may anticipate challenging airway situations. Consultation of previous anesthesia records is of a valuable help; however, the airway must be reassessed before any new airway manipulation. The degree of severity of mandibular hypoplasia correlates with difficult tracheal intubation. Virtual imaging using 3D CT or cone-beam computed tomography may be indicated for selected patients to assess the airway anatomy looking for anomalies [34].

Facemask ventilation is challenging in children with Goldenhar's syndrome due to a poor mask seal, often requiring the use of a gauze with self-adhesive tape to provide an adequate seal. The reason for this poor mask fit is the facial asymmetry and the presence of a soft tissue slit extended from the side of the mouth to the middle of the cheek on the abnormal hemi-face.

**169**

laryngoscope.

*An Approach to the Airway Management in Children with Craniofacial Anomalies*

Tracheal intubation is usually more difficult to achieve than maintaining airway

Although fiberoptic intubation (FOB) technique is one of the popular options for securing difficult airways of patients with GS, various strategies can be adopted successfully to perform tracheal intubation; however, it is recommended that the airway operator sticks with the tool and technique that is the most familiar to his practice. These include: FOB through LMA (video-assisted fiberoptic intubation (VAFI)), GlideScope, Air-Q, Airtraq, C-MAC D-blade or C-MAC Miller-blade videolaryngoscopy, Pentax-AWS Airwayscope with tracheal introducer, Laryngeal Mask Airway helped by Pediatric Boussignac Bougie or retrograde tracheal intubation. The Truview PCD® laryngoscopy has proven its effectiveness and offers the advantage of continuously supplying oxygen via its oxygenation side port during the procedure. When the intubation is not required, LMA or nasopharyngeal airway

*Overview:* it was initially described by Klippel and Feil in 1912 as a clinical triad

*Genetics*: Klippel-Feil syndrome is an inherited autosomal dominant condition. It is the result of an anomalous partition of the cervical somites during embryogenesis

*Clinical considerations*: KFS is classified into three classes according to the level and severity of the spine fusion, with type 1 representing a considerable fusion of numerous cervical vertebrae, type 2 representing fusions of one or two cervical vertebrae, and type 3 representing cervical vertebrae fusions combined with thoracic

KPS may be related to other anomalies such as cranio-facial deformities includ-

Neurological deficits with hyperlaxed cervical spines and neuro-degeneration

*Airway and anesthetic implications*: KFS is often associated with difficult intubation, evidently because of the fixed neck which does not allow proper extension of the atlanto-axial joint during laryngoscopy and the subsequent advanced Cormack-Lehane view. Many reports describe a grade 4 view with a conventional

ing craniosynostosis, cleft lip, micrognathia, and laryngeal defects. Thoracic deformities such as scoliosis may be present in addition to other skeletal deformities like scapular elevation (Sprengel's). Uro-genital malformations are commonly pres-

Screening patients at risk for cervical spine instability is a crucial step before airway management in order to avoid spinal injury, especially those with

ent as well as congenital heart defects most commonly the VSD.

with fused spines are commonly associated with KPS [17].

of an extremely short "compressed" neck, a low hairline at the rear end of the skull, and a limited mobility of the neck caused by fusion of two or more cervical vertebrae. Despite being discovered as a triad, it is not uncommon for patients with KFS to meet just one clinical criterion of the above. It may be associated with other

*Incidence*: KFS has a prevalence of 1:40000 to 1:42000 of live births.

patency, especially in the case right-sided hemifacial microsomia. Several combined conditions may contribute to difficult intubation, including retrognathia, micrognathia, asymmetrical hypoplasia of the mandible, limited mouth opening, palatal anomalies, potentially associated vertebral defects, and limited neck motion. The hypoplastic mandible reduces the retromandibular space. The relatively bulky tongue is displaced posteriorly overhanging the larynx, thus making visualization of the vocal inlets difficult, even nearly impossible during conventional

*DOI: http://dx.doi.org/10.5772/intechopen.93426*

constitutes a possible alternative [1, 35, 36].

between the third and eighth week of gestation.

**4.6 Klippel-Feil syndrome (KFS)**

and/or lumbar vertebral fusions.

anomalies (**Figure 6**).

laryngoscopy.

*An Approach to the Airway Management in Children with Craniofacial Anomalies DOI: http://dx.doi.org/10.5772/intechopen.93426*

Tracheal intubation is usually more difficult to achieve than maintaining airway patency, especially in the case right-sided hemifacial microsomia. Several combined conditions may contribute to difficult intubation, including retrognathia, micrognathia, asymmetrical hypoplasia of the mandible, limited mouth opening, palatal anomalies, potentially associated vertebral defects, and limited neck motion. The hypoplastic mandible reduces the retromandibular space. The relatively bulky tongue is displaced posteriorly overhanging the larynx, thus making visualization of the vocal inlets difficult, even nearly impossible during conventional laryngoscopy.

Although fiberoptic intubation (FOB) technique is one of the popular options for securing difficult airways of patients with GS, various strategies can be adopted successfully to perform tracheal intubation; however, it is recommended that the airway operator sticks with the tool and technique that is the most familiar to his practice. These include: FOB through LMA (video-assisted fiberoptic intubation (VAFI)), GlideScope, Air-Q, Airtraq, C-MAC D-blade or C-MAC Miller-blade videolaryngoscopy, Pentax-AWS Airwayscope with tracheal introducer, Laryngeal Mask Airway helped by Pediatric Boussignac Bougie or retrograde tracheal intubation. The Truview PCD® laryngoscopy has proven its effectiveness and offers the advantage of continuously supplying oxygen via its oxygenation side port during the procedure. When the intubation is not required, LMA or nasopharyngeal airway constitutes a possible alternative [1, 35, 36].

#### **4.6 Klippel-Feil syndrome (KFS)**

*Special Considerations in Human Airway Management*

(high arch or cleft) and tongue anomalies are often associated. Additionally, almost 50% of children with Goldenhar's syndrome may have vertebral defects, especially at the cervical level, such as hemivertebrae or hypoplasia, along with a potential risk of subluxation at the atlanto-occipital joint. Neck movements are limited during flexion and extension, increasing the rate of difficult or failed tracheal intubation procedure. Congenital cardiac structural malformations (Tetralogy of Fallot and septal defects) are present in about one third of the cases. In rare cases, some degrees of mental retardation and other systemic anomalies, mainly genitourinary,

*Goldenhar's syndrome before and after surgical procedure for lip and palatoplasty, correction of macrostomia and nasal septum deformity, excision of pre-auricular tags: (A) preoperative; (B) postoperative [32].*

*Airway and anesthetic implications*: anesthesia or sedation may be provided for children with Goldenhar's syndrome for various procedures (ear reconstruction, distraction osteogenesis, soft tissue reconstruction, skin graft, cardiac, etc.).

The anesthetic management is risky because of the difficult airway. The degree of difficulties depends directly on the severity of craniofacial anomalies and associated vertebral defects and tends to worsen progressively with increasing age. Detecting patients at risk in the preoperative setting may anticipate challenging airway situations. Consultation of previous anesthesia records is of a valuable help; however, the airway must be reassessed before any new airway manipulation. The degree of severity of mandibular hypoplasia correlates with difficult tracheal intubation. Virtual imaging using 3D CT or cone-beam computed tomography may be indicated

Facemask ventilation is challenging in children with Goldenhar's syndrome due to a poor mask seal, often requiring the use of a gauze with self-adhesive tape to provide an adequate seal. The reason for this poor mask fit is the facial asymmetry and the presence of a soft tissue slit extended from the side of the mouth to the

for selected patients to assess the airway anatomy looking for anomalies [34].

pulmonary, and vascular are reported [4, 6, 7, 17].

middle of the cheek on the abnormal hemi-face.

**168**

**Figure 5.**

*Overview:* it was initially described by Klippel and Feil in 1912 as a clinical triad of an extremely short "compressed" neck, a low hairline at the rear end of the skull, and a limited mobility of the neck caused by fusion of two or more cervical vertebrae. Despite being discovered as a triad, it is not uncommon for patients with KFS to meet just one clinical criterion of the above. It may be associated with other anomalies (**Figure 6**).

*Genetics*: Klippel-Feil syndrome is an inherited autosomal dominant condition. It is the result of an anomalous partition of the cervical somites during embryogenesis between the third and eighth week of gestation.

*Incidence*: KFS has a prevalence of 1:40000 to 1:42000 of live births.

*Clinical considerations*: KFS is classified into three classes according to the level and severity of the spine fusion, with type 1 representing a considerable fusion of numerous cervical vertebrae, type 2 representing fusions of one or two cervical vertebrae, and type 3 representing cervical vertebrae fusions combined with thoracic and/or lumbar vertebral fusions.

KPS may be related to other anomalies such as cranio-facial deformities including craniosynostosis, cleft lip, micrognathia, and laryngeal defects. Thoracic deformities such as scoliosis may be present in addition to other skeletal deformities like scapular elevation (Sprengel's). Uro-genital malformations are commonly present as well as congenital heart defects most commonly the VSD.

Neurological deficits with hyperlaxed cervical spines and neuro-degeneration with fused spines are commonly associated with KPS [17].

*Airway and anesthetic implications*: KFS is often associated with difficult intubation, evidently because of the fixed neck which does not allow proper extension of the atlanto-axial joint during laryngoscopy and the subsequent advanced Cormack-Lehane view. Many reports describe a grade 4 view with a conventional laryngoscope.

Screening patients at risk for cervical spine instability is a crucial step before airway management in order to avoid spinal injury, especially those with

#### **Figure 6.**

*Child with Klippel-Feil syndrome and anomaly of the Occipito-cervical junction. The images show an elevated left shoulder due to a Sprengel anomaly, a short, webbed neck, and a low hairline (scar on the thorax after surgical repair of nonrestrictive atrial septal defect) [37].*

hyperlaxed spines who may require C-spine precautions with in-line-stabilization during intubation. This is performed via a lateral neck X-ray in flexion and extension positions [1, 4–7].

Obstructive sleep apnea (OSA) is not uncommonly encountered in patients with KFS, hence a preoperative sleep study may be indicated along with postoperative apnea monitor. A preoperative echocardiography must be considered especially in patients with pulmonary hypertension secondary to OSA and scoliosis.

A history of previous smooth intubation in KPS patient does not implicate a future favorable outcome due to the progressive nature of the disease. Hence, a careful preoperative assessment and planning is critical for safe airway management.

Bag-mask ventilation is likely difficult in those patients as well as direct laryngoscopy owing to the fixed neck or the in-line neck stabilization.

Should the older child be cooperative enough to sustain an awake fiberoptic intubation (with light sedation) that would be the approach of choice avoiding both the risks of difficult ventilation and neck injury secondary to airway manipulation.

Otherwise, a plan to preserve spontaneous ventilation during anesthetic induction should be performed with either total intravenous anesthesia (TIVA) or inhaled Sevoflurane (IV Dexmedetomidine and IV Ketamine can be used as well) avoiding the use of neuro-muscular blockers.

A trial of manual bag-mask to assess for ventilation is used by some practitioners before airway manipulation. The various arrays of airway tools including videoscopes (Glidescope/C-MAC etc.) as well as the fiberoptic bronchoscope have been used successfully for intubation in patients with KFS. They are preferred as first line intubation technique due to the lower incidence of cervical spine mobilization when used.

**171**

**Figure 7.**

*An Approach to the Airway Management in Children with Craniofacial Anomalies*

to the severity of their cardio-pulmonary and airway pathology.

impose challenges to airway management (**Figure 7**).

*Incidence:* 1 per 13,700–15,000 of live births.

and adrenal carcinoma has been observed [6, 7, 17].

*Macroglossia in the patient with Beckwith-Wiedemann syndrome after intubation [38].*

If the patient is on a home BIPAP, it will be required after extubation.

*Overview:* it was initially reported by J Bruce Beckwith and Hans-Rudolf Wiedemann. It is one of the syndromes associated with a huge tongue that may

*Genetics:* it is caused by genetic alterations on chromosome 11p15 region.

*Clinical considerations:* Beckwith-Wiedemann syndrome is characterized by a clinical tetrad of macroglossia (Most common), omphalocele, umbilical hernia, and

*Airway and anesthetic implications*: the main anesthetic considerations in BWS are abnormal airway anatomy, hypoglycemia, and cardiac anomalies (cardiomegaly and other cardiac structural defects). A detailed pre-operative assessment of the airway, the cardiac, and the urinary system is mandatory. Visceromegaly may shift the diaphragm upward reducing functional residual capacity. Associated congenital malformations, prematurity, and interventions early in life may complicate anesthetic management. These children frequently require corrective surgical

These children are associated with exomphalos, macroglossia, gigantism, macrosomia, visceromegaly, horizontal earlobe creases, renal medullary dysplasia, cardiac malformations, hypoglycemia, hypothyroidism, hyperlipidemia, polycythemia, hypercalciuria, and embryonal tumors. The presence of three features out of the above will confirm the clinical diagnosis of BWS after ruling out the clinical features of overgrowth syndromes. The risk for embryonal tumor development especially hepatoblastoma, neuroblastoma, rhabdomyosarcoma, gonadoblastoma,

It is important to keep in mind that the option of an emergency surgical airway such as cricothyrotomy/tracheostomy is very limited in patients with KFS due to the extremely short neck, thus the airway approach must be very carefully planned. Extubation must only be attempted when the patient is fully awake and in the presence of protective airway reflexes. An opioid-sparing anesthetic technique is recommended (regional anesthesia whenever possible) as the presence of OSA may increase narcotic-sensitivity. KFS patients should preferably be monitored in the post-operative setting in a high dependency unit or an intensive care unit according

*DOI: http://dx.doi.org/10.5772/intechopen.93426*

**4.7 Beckwith-Wiedemann syndrome**

neonatal hypoglycemia.

#### *An Approach to the Airway Management in Children with Craniofacial Anomalies DOI: http://dx.doi.org/10.5772/intechopen.93426*

It is important to keep in mind that the option of an emergency surgical airway such as cricothyrotomy/tracheostomy is very limited in patients with KFS due to the extremely short neck, thus the airway approach must be very carefully planned.

Extubation must only be attempted when the patient is fully awake and in the presence of protective airway reflexes. An opioid-sparing anesthetic technique is recommended (regional anesthesia whenever possible) as the presence of OSA may increase narcotic-sensitivity. KFS patients should preferably be monitored in the post-operative setting in a high dependency unit or an intensive care unit according to the severity of their cardio-pulmonary and airway pathology.

If the patient is on a home BIPAP, it will be required after extubation.

#### **4.7 Beckwith-Wiedemann syndrome**

*Special Considerations in Human Airway Management*

hyperlaxed spines who may require C-spine precautions with in-line-stabilization during intubation. This is performed via a lateral neck X-ray in flexion and exten-

*Child with Klippel-Feil syndrome and anomaly of the Occipito-cervical junction. The images show an elevated left shoulder due to a Sprengel anomaly, a short, webbed neck, and a low hairline (scar on the thorax after*

A history of previous smooth intubation in KPS patient does not implicate a future favorable outcome due to the progressive nature of the disease. Hence, a careful preoperative assessment and planning is critical for safe airway

Bag-mask ventilation is likely difficult in those patients as well as direct laryn-

Should the older child be cooperative enough to sustain an awake fiberoptic intubation (with light sedation) that would be the approach of choice avoiding both the risks of difficult ventilation and neck injury secondary to airway

Otherwise, a plan to preserve spontaneous ventilation during anesthetic induc-

A trial of manual bag-mask to assess for ventilation is used by some practitioners

tion should be performed with either total intravenous anesthesia (TIVA) or inhaled Sevoflurane (IV Dexmedetomidine and IV Ketamine can be used as well)

before airway manipulation. The various arrays of airway tools including videoscopes (Glidescope/C-MAC etc.) as well as the fiberoptic bronchoscope have been used successfully for intubation in patients with KFS. They are preferred as first line intubation technique due to the lower incidence of cervical spine mobilization

patients with pulmonary hypertension secondary to OSA and scoliosis.

goscopy owing to the fixed neck or the in-line neck stabilization.

avoiding the use of neuro-muscular blockers.

Obstructive sleep apnea (OSA) is not uncommonly encountered in patients with KFS, hence a preoperative sleep study may be indicated along with postoperative apnea monitor. A preoperative echocardiography must be considered especially in

**170**

when used.

sion positions [1, 4–7].

*surgical repair of nonrestrictive atrial septal defect) [37].*

management.

**Figure 6.**

manipulation.

*Overview:* it was initially reported by J Bruce Beckwith and Hans-Rudolf Wiedemann. It is one of the syndromes associated with a huge tongue that may impose challenges to airway management (**Figure 7**).

*Genetics:* it is caused by genetic alterations on chromosome 11p15 region. *Incidence:* 1 per 13,700–15,000 of live births.

*Clinical considerations:* Beckwith-Wiedemann syndrome is characterized by a clinical tetrad of macroglossia (Most common), omphalocele, umbilical hernia, and neonatal hypoglycemia.

These children are associated with exomphalos, macroglossia, gigantism, macrosomia, visceromegaly, horizontal earlobe creases, renal medullary dysplasia, cardiac malformations, hypoglycemia, hypothyroidism, hyperlipidemia, polycythemia, hypercalciuria, and embryonal tumors. The presence of three features out of the above will confirm the clinical diagnosis of BWS after ruling out the clinical features of overgrowth syndromes. The risk for embryonal tumor development especially hepatoblastoma, neuroblastoma, rhabdomyosarcoma, gonadoblastoma, and adrenal carcinoma has been observed [6, 7, 17].

*Airway and anesthetic implications*: the main anesthetic considerations in BWS are abnormal airway anatomy, hypoglycemia, and cardiac anomalies (cardiomegaly and other cardiac structural defects). A detailed pre-operative assessment of the airway, the cardiac, and the urinary system is mandatory. Visceromegaly may shift the diaphragm upward reducing functional residual capacity. Associated congenital malformations, prematurity, and interventions early in life may complicate anesthetic management. These children frequently require corrective surgical

interventions in infancy such as tongue reduction surgeries, hernia repair, exomphalos repair or hepatectomy.

Preoperative assessment should include a careful evaluation of the airway focusing on the mouth opening, tongue size, and preoperative head and neck imaging if required. It should focus also on other systems involvement such as the heart, hence an echocardiography is recommended. The genito-urinary system and the liver must be evaluated in addition to the preoperative glucose homeostasis.

The major challenge during airway management of a patient with Beckwith-Wiedemann syndrome pertains to the huge tongue which might completely obstruct the airway with anesthetic induction rendering the bag-mask ventilation and intubation difficult to perform [39, 40].

Hence a careful plan A, with a backup plan B and a plan C must be organized beforehand. An intravenous line is recommended to be secured before induction. Keeping spontaneous ventilation is considered to be the safest approach to the airway that can be achieved with intravenous anesthetics or inhalational Sevoflurane and by avoiding non-depolarizing neuro-muscular blockers. Some practices may use muscle relaxants after making sure of the ability to ventilate by a trial of ventilation after induction. Sugammadex muscle (rocuronium antidote) has allowed more confidence for anesthesiologists to give muscle relaxants in order to facilitate intubation.

A variety of tools can be used for intubation ranging from the direct laryngoscopes aided by a Gum elastic Bougie or a stylet, to the Videoscopes including the C-MAC and the Glidescope, to the fiberoptic bronchoscope.

A plan B consists of inserting a laryngeal mask airway should ventilation become problematic, and in case of the latter's failure, a plan C with a surgical airway must be immediately implemented.

Extubation must only occur when patient is fully awake and may be helped with a nasopharyngeal airway "in-situ" to help overcoming the tongue's obstruction in the immediate post-operative period. Patients with BWS must have a post-operative monitoring after surgery in the high dependency area or the intensive care unit.

#### **4.8 Mucopolysaccharidosis (MPS)**

*Overview*: the mucopolysaccharidoses (MPS) are a set of storage diseases caused by a disordered or absent lysosomal hydroxylase enzyme leading to the build-up of muco-polysaccharides (glycosaminoglycans (GAG)) in the connective tissues, the musculo-skeletal system and the visceral organs. They are classified as seven syndromes with each involving a mix of 11 enzymatic disorders [41]. Mucopolysaccharidoses patients are associated with a high incidence of difficult bag-mask ventilation which represents the "nightmare" for the anesthesiologist or the airway operator.

*Incidence*: as a rare set of conditions, MPS accounts for less than 0.1% of all genetic but have been reported throughout the world in various forms. Region and ethnic background may affect the phenotype of MPS.

*Genetic*: inheritance autosomal recessive.

*Pathophysiology*: the mutation in lysosomal hydroxylase enzyme leads to an impaired metabolism of mucopolysaccharides (GAG) which will accumulate in multiple body tissues leading to macroglossia, adenotonsillar hypertrophy, and laryngeal/tracheal tissue distortion and narrowing.

Some types of MPS (Type1: Hurler, Type 4: Morquio, and Type 6: Maroteaux-Lamy) may be associated with atlantoaxial subluxation and odontoid hypoplasia which may lead to spinal cord compression with subsequent neurological deficit. Accumulation in the cervical spines may lead to a short and fixed neck. The

**173**

*An Approach to the Airway Management in Children with Craniofacial Anomalies*

temporo-mandibular joint may get affected with restricted mobility. Deposition of mucopolysaccharides in the heart and vascular tissues may lead to cardiomyopa-

*Clinical considerations and airway management*: difficult ventilation and intubation are common concerns in patients with mucopolysaccharidoses as the thick and uncompliant infiltrated tissues (skin, tongue, and mucous membranes of the airway, bones, and joints) may render the natural airway narrow and not distensible by the positive pressure ventilation applied by the bag-mask. Laryngoscopy is often challenging due to difficult manipulation of the laryngoscope as a result of the stiff and thick tissues. The large tongue, the hypertrophied tonsils, and the limited mouth opening are caused by the immobile temporo-mandibular joints [40]. This effect is compounded if there is a subluxation of the atlanto-axial joint or cervicalspine affection which mandates an in-line-stabilization during airway management. A narrow/distorted trachea may prevent an appropriately sized endotracheal

Fortunately, the enzymatic replacement therapy may hinder the progression of the disease, hence an adequately treated mucopolysaccharidosis patient may have a

Preoperatively, the MPS patient must be well assessed for the extent of the disease as well as a focused airway assessment including the mouth opening, tongue and tonsillar size, presence of obstructive sleep apnea (which is very common in MPS), and pulmonary hypertension. A preoperative echocardiography is essential to rule out any associated cardiomyopathy. Patients with MPS type 1 (Hurler), 4 (Morquio), and 6 must be checked for any cervical spine or atlanto-

Intravenous cannulation in MPS patients may be challenging due to the thick infiltrated skin, hence a preoperatively inserted intravenous line before anesthetic

Spontaneous ventilation must be maintained during induction of anesthesia due to the high risk of difficult ventilation in case of apnea. This could be achieved with either intravenous or inhalational induction agents and by avoiding neuro-muscular

An LMA must be used as a second plan whenever encountering difficulties in

Video-laryngoscopies are other favorable options for intubation in MPS patients especially those with unstable cervical spine owing to the lesser risk of neck mobilization when used. Establishment of a surgical airway access such as tracheostomy may be difficult due to the thick tissues and the associated tracheal deformities.

Vascular anomalies are disorders of abnormal vasculogenesis or lymphogenesis. They can involve any part of body and can present in any phase of development. They include different types according to histopathology and anatomical site.

VMs may be with other syndromic malformations such as Parkes-Weber, Sturge-Weber, Klippel-Trenaunay Servelle-Martorell, PHACE and LUMBAR syndromes.

*Overview*: infantile hemangioma (IH) is the most prevalent vascular anomaly of the head and neck. It may cause a life-threatening airway obstruction if located in

ventilation; it can also be used to facilitate fiberoptic intubation.

**5. Craniofacial vascular malformations (VMs)**

*DOI: http://dx.doi.org/10.5772/intechopen.93426*

thies, arrhythmias, and pulmonary hypertension [5].

tube from passing throughout the vocal cords.

axial instability [42].

induction is preferable.

**5.1 Subglottic hemangiomas**

the glottic/subglottic area.

blockers.

lesser risk of difficult airway than the untreated patient.

#### *An Approach to the Airway Management in Children with Craniofacial Anomalies DOI: http://dx.doi.org/10.5772/intechopen.93426*

temporo-mandibular joint may get affected with restricted mobility. Deposition of mucopolysaccharides in the heart and vascular tissues may lead to cardiomyopathies, arrhythmias, and pulmonary hypertension [5].

*Clinical considerations and airway management*: difficult ventilation and intubation are common concerns in patients with mucopolysaccharidoses as the thick and uncompliant infiltrated tissues (skin, tongue, and mucous membranes of the airway, bones, and joints) may render the natural airway narrow and not distensible by the positive pressure ventilation applied by the bag-mask. Laryngoscopy is often challenging due to difficult manipulation of the laryngoscope as a result of the stiff and thick tissues. The large tongue, the hypertrophied tonsils, and the limited mouth opening are caused by the immobile temporo-mandibular joints [40]. This effect is compounded if there is a subluxation of the atlanto-axial joint or cervicalspine affection which mandates an in-line-stabilization during airway management.

A narrow/distorted trachea may prevent an appropriately sized endotracheal tube from passing throughout the vocal cords.

Fortunately, the enzymatic replacement therapy may hinder the progression of the disease, hence an adequately treated mucopolysaccharidosis patient may have a lesser risk of difficult airway than the untreated patient.

Preoperatively, the MPS patient must be well assessed for the extent of the disease as well as a focused airway assessment including the mouth opening, tongue and tonsillar size, presence of obstructive sleep apnea (which is very common in MPS), and pulmonary hypertension. A preoperative echocardiography is essential to rule out any associated cardiomyopathy. Patients with MPS type 1 (Hurler), 4 (Morquio), and 6 must be checked for any cervical spine or atlantoaxial instability [42].

Intravenous cannulation in MPS patients may be challenging due to the thick infiltrated skin, hence a preoperatively inserted intravenous line before anesthetic induction is preferable.

Spontaneous ventilation must be maintained during induction of anesthesia due to the high risk of difficult ventilation in case of apnea. This could be achieved with either intravenous or inhalational induction agents and by avoiding neuro-muscular blockers.

An LMA must be used as a second plan whenever encountering difficulties in ventilation; it can also be used to facilitate fiberoptic intubation.

Video-laryngoscopies are other favorable options for intubation in MPS patients especially those with unstable cervical spine owing to the lesser risk of neck mobilization when used. Establishment of a surgical airway access such as tracheostomy may be difficult due to the thick tissues and the associated tracheal deformities.


**7. Summary**

We have reviewed various studies with regard to the understanding of pathomechanism of infertility in endometriosis, based on its impacts on number of pathologic conditions, such as: pelvic adhesion and endometrioma, abnormal folliculogenesis and impaired oocyte function, altered sperm function, reduced embryo quality, and impaired endometrium receptivity. The controversy regarding whether endometriosis is a cause of infertility or an incidental finding is ongoing.

Based on several studies reviewed above showed that peritoneal microenvironment of women with endometriosis which contain pro-inflammatory factor and ROS is the main causative factor of the pathomechanism of infertility in endometriosis. They have a key role through autocrine-paracrine communication alteration in the mechanism of pelvic adhesion, abnormal folliculogenesis, reduced oocyte/embryo quality, reduced sperm fuction and implantaion impairment (see figure 2). We hope that the increase of our understanding on the above pathomechanism can increase our attention to the improvement of the complex management of infertility in endometriosis.

### **8. Acknowledgments**

The author would like to thank Prof Lila Dewata and Prof Samsulhadi for their assistance in the preparation of the manuscript.

#### **9. References**

350 Endometriosis - Basic Concepts and Current Research Trends

in the adhesion of blastocysts to the luminal epithelium. Scanning electron microscopy in sequential endometrial biopsies showed that pinopodes formed briefly (1–2 days) and that their numbers correlate with implantation (Nikas *et al.,* 1999). Garcia-Velasco (2001) found pinopode expression in women with endometriosis did not differ from that of patients without endometriosis undergoing artificial cycles. Similarly, the clinical outcome in these women was comparable to that of the general population included in the oocyte donation program and this study stated that pinopode expression is not altered, suggesting that endometrial receptivity in women with this disease remains unaltered (Garcia-Velasco *et al*.,

Endometrial aspects and molecular studies on the receptivity status of endometrium resulted in conflicting data. Several studies suggest that an altered follicular microenvironment could be responsible for a defective folliculogenesis, and subsequently reduced oocyte/embryo quality, and in turn, result in altered embryo implantation but the

Fig. 2. Pathomechanism of infertility in endometriosis (Hendarto, 2011)

We have reviewed various studies with regard to the understanding of pathomechanism of infertility in endometriosis, based on its impacts on number of pathologic conditions, such as: pelvic adhesion and endometrioma, abnormal folliculogenesis and impaired oocyte function, altered sperm function, reduced embryo quality, and impaired endometrium receptivity. The controversy regarding whether endometriosis is a cause of infertility or an

2001).

**7. Summary**

incidental finding is ongoing.

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**19**

*China*

*Xinjiang Medical University,*

**Analysis of Differential Genes of Uyghur Women with Endometriosis in Xinjiang**

Aixingzi Aili, Ding Yan, Hu Wenjing, Yang Xinhua and Hanikezi Tuerxun

Endometriosis (EM) is a common and important health problem, it is estimated to be present in 10%-15% of women in the reproductive age group and 25%-35% of infertile women. In the First Affiliated Hospital of Xinjiang Medical University in China, 447 cases primaily diagnosed with surgically confirmed endometriosis between January 2000 to September 2005, among them 349 cases of endometriosis were Han Chinese (78.1%) and 69

Xinjiang is the biggest province of China inhabited by ethnic minorities in which Uyghur people are accounted for more than 40% of the total population. In recent years, the number of the Uyghur women with endometriosis have been increased in Xinjiang, however still clearly less than Han chinese with endometriosis. The data from pathology deparment of the First Affiliated Hospital of Xinjiang Medical University between 1992 and 1996 showed that there were only three Uyghur women with endometriosis (5.76%) among 52 cases. Between 2000 and 2001, only 4 Uyghur women with endometriosis (3.1%) among 128 patients. Between 2003 and 2010, there were 73 Uyghur women (13.45%) with endometriosis

**1. Introduction**

Fig. 1.

cases Uyghur women with endometriosis (15.3%).


**5. SOCS molecules and cytokine signalling pathways**

As discussed in the previous section, a diversity of signalling cascades are involved in regu‐ lating neuronal cell proliferation, differentiation and survival. However, JAK-STAT signal‐ ling seems to be one of the central pathways in the regulation of adult neurogenesis. Since its discovery twenty years ago, this pathway has been studied extensively due to its key roles in modulating many different physiological processes through responses to various regulatory molecules [146].

neurogenic niche [50]. Further, it has an important role in the positive regulation of reactive

Regulation of Basal and Injury-Induced Fate Decisions of Adult Neural Precursor Cells: Focus on SOCS2 and Related

Signalling Pathways

249

http://dx.doi.org/10.5772/53268

An important aspect to cytokine signalling via a pathway such as JAK-STAT is the need for its downregulation following activation. Thus far, JAK-STAT signalling is known to be neg‐ atively regulated by protein inhibitors of activated STATs (PIAS), the SH2-containing pro‐ tein tyrosine phosphatases (SHPs) and suppressors of cytokine signalling (SOCS) proteins [160]. In this section, SOCS proteins will be the focus of discussion as the negative regulation of the JAK-STAT signalling pathway by SOCS has several effects on the regulation of neuro‐

The SOCS family consists of eight members, namely, SOCS1-7 and cytokine-inducible Src homology 2 (SH2) protein (CIS). They are characterised by a central SH2 domain, a C-termi‐ nal SOCS box and a variable N-terminal domain. In addition to these, SOCS1 and SOCS3 also contain a small kinase inhibitory domain. CIS was the first member of this protein fami‐ ly to be cloned. It is also unique to the rest of the SOCS family as a result of its SH2 domain

SOCS expression is induced following activation of the JAK-STAT pathway. This initiates a classic negative feedback loop whereby the SOCS proteins activated by JAK-STAT signal‐ ling now go on to inhibit it. SOCS proteins achieve downregulation of signalling by binding to tyrosine phosphorylated proteins via their SH2 domain. The exact mechanism by which signalling inhibition is achieved varies depending on the SOCS protein in question. For ex‐ ample, SOCS1 and SOCS3 both work to block the kinase activity of activated JAK proteins. In the case of SOCS1, this is achieved by directly binding and blocking access to the activat‐ ed JAK. In the case of SOCS3, this is achieved by its binding to the activated gp130 receptor such that STAT proteins can no longer dock onto the phosphorylated tyrosine residues and be activated by JAK. One mechanism of action for SOCS2 is by blocking STAT access to the

SOCS proteins are also able to regulate activity of target proteins, including other SOCS pro‐ teins, through interaction with their SOCS box [163, 164]. Interestingly, SOCS2, SOCS6 and SOCS7 have the potential to interact with all members of the SOCS protein family including themselves [164]. In terms of SOCS2, when expressed at high levels, it is able to inhibit the action of SOCS1 and SOCS3 by targeting them for proteasomal degradation [164]. This has also been proposed as a mechanism for the dual action of SOCS2 on GH signalling as ob‐ served in the overgrowth phenotypes of SOCS2 knockout and overexpressing mice descri‐

Signalling via the JAK-STAT pathway has an important role in neural precursor prolifera‐ tion and differentiation [153, 166-168]. Following the discovery that SOCS proteins regulate the JAK-STAT pathway, the next obvious step was to examine them for possible roles in the nervous system. In doing so, analysis of the SOCS family gene expression in the developing mouse forebrain brought SOCS2 into the spotlight [168]. The genes SOCS1 – SOCS3 and CIS

which differs in a few amino acids from most all other known SH2 domains [161].

astrocytes in the injured CNS [159].

**5.2. The suppressors of cytokine signalling**

genesis and NPC fate.

activated receptor [162].

bed below [165].

#### **5.1. JAK/STAT signalling**

The JAK-STAT pathway can be activated by a range of cytokines, growth factors and hor‐ mones. In the regulation of adult neurogenesis, activation of this pathway is carried out by a group of neuroregulatory cytokines. Members of this cytokine group include CNTF, LIF and cardiotrophin 1 (CT-1), all of which belong to the interleukin 6 family of cytokines. These cyto‐ kines initiate JAK-STAT activation by binding and signalling through the LIF receptor-β (LIFRβ)/ glycoprotein 130 (gp130) receptor complex. The receptor complex bound by CNTF differs slightly in that it has a third extracellular receptor component, the CNTF receptor-α (structurally related to gp130), that is held to the membrane via a glycosylphosphoinositol [147].

Cytokine binding results in the dimerization of LIFRβ and gp130 receptors to form a com‐ plex [148]. This initiates autophosphorylation and activation of JAK proteins which are asso‐ ciated with the intracellular domains of the LIFRβ and gp130 receptors [149]. Members of the JAK protein family include JAK1, JAK2, JAK3 and TYK2. Cytokines signalling through the LIFRβ/gp130 pathway have been found to activate at least JAK1, JAK2 and TYK2 [150]. In terms of the CNS, only JAK1 and JAK2 expression has been found at significant levels [151]. JAK2 is highly expressed in the developing brain compared to JAK1, thus, a role for it in the regulation of neurogenesis in the developing brain has been suggested [151].

After activation, JAKs phosphorylate tyrosine residues in the intracellular domains of LIFRβ and gp130. These phosphorylated residues become binding sites for SH2 domain containing proteins such as STAT. STAT proteins are a family of transcription factors comprised of STAT1, STAT2, STAT3, STAT4, STAT5a, STAT5b and STAT6 [152]. Upon binding to the ac‐ tivated receptor complex, STAT proteins are phosphorylated by JAKs resulting in their di‐ merization. Dimerized STAT proteins are now able to translocate into the nucleus and induce gene expression of target neural genes such as glial fibrillary acidic protein (GFAP), peripherin and vasoactive intestinal peptide [46]. Other SH2 domain containing proteins can also bind the activated LIFRβ/gp130 receptor complex to activate the Ras/MAPK and PI-3K/Akt signalling pathways [49].

The LIFRβ/gp130 pathway is essential for the regulation of astrogliogenesis in the develop‐ ing and adult brain. In cultured cortical precursors, CNTF, LIF and CT-1 all promote astro‐ cyte formation through LIFRβ/gp130 activation [153-155]. Integral to this pathway is signalling via STAT3, as highlighted by the observation that STAT3 activation in neural stem cells induces glial differentiation, while its inhibition promotes a neuronal fate [156, 157]. Also, in neuroepithelial cells, STAT3 activation promotes astrogliogenisis via LIF in‐ duced bone morphogenetic protein 2 expression [158]. In addition to regulating astroglio‐ genesis, STAT3 induction by CNTF was found to be essential in the maintenance of the SGZ neurogenic niche [50]. Further, it has an important role in the positive regulation of reactive astrocytes in the injured CNS [159].

An important aspect to cytokine signalling via a pathway such as JAK-STAT is the need for its downregulation following activation. Thus far, JAK-STAT signalling is known to be neg‐ atively regulated by protein inhibitors of activated STATs (PIAS), the SH2-containing pro‐ tein tyrosine phosphatases (SHPs) and suppressors of cytokine signalling (SOCS) proteins [160]. In this section, SOCS proteins will be the focus of discussion as the negative regulation of the JAK-STAT signalling pathway by SOCS has several effects on the regulation of neuro‐ genesis and NPC fate.

#### **5.2. The suppressors of cytokine signalling**

ling seems to be one of the central pathways in the regulation of adult neurogenesis. Since its discovery twenty years ago, this pathway has been studied extensively due to its key roles in modulating many different physiological processes through responses to various

The JAK-STAT pathway can be activated by a range of cytokines, growth factors and hor‐ mones. In the regulation of adult neurogenesis, activation of this pathway is carried out by a group of neuroregulatory cytokines. Members of this cytokine group include CNTF, LIF and cardiotrophin 1 (CT-1), all of which belong to the interleukin 6 family of cytokines. These cyto‐ kines initiate JAK-STAT activation by binding and signalling through the LIF receptor-β (LIFRβ)/ glycoprotein 130 (gp130) receptor complex. The receptor complex bound by CNTF differs slightly in that it has a third extracellular receptor component, the CNTF receptor-α (structurally related to gp130), that is held to the membrane via a glycosylphosphoinositol

Cytokine binding results in the dimerization of LIFRβ and gp130 receptors to form a com‐ plex [148]. This initiates autophosphorylation and activation of JAK proteins which are asso‐ ciated with the intracellular domains of the LIFRβ and gp130 receptors [149]. Members of the JAK protein family include JAK1, JAK2, JAK3 and TYK2. Cytokines signalling through the LIFRβ/gp130 pathway have been found to activate at least JAK1, JAK2 and TYK2 [150]. In terms of the CNS, only JAK1 and JAK2 expression has been found at significant levels [151]. JAK2 is highly expressed in the developing brain compared to JAK1, thus, a role for it

After activation, JAKs phosphorylate tyrosine residues in the intracellular domains of LIFRβ and gp130. These phosphorylated residues become binding sites for SH2 domain containing proteins such as STAT. STAT proteins are a family of transcription factors comprised of STAT1, STAT2, STAT3, STAT4, STAT5a, STAT5b and STAT6 [152]. Upon binding to the ac‐ tivated receptor complex, STAT proteins are phosphorylated by JAKs resulting in their di‐ merization. Dimerized STAT proteins are now able to translocate into the nucleus and induce gene expression of target neural genes such as glial fibrillary acidic protein (GFAP), peripherin and vasoactive intestinal peptide [46]. Other SH2 domain containing proteins can also bind the activated LIFRβ/gp130 receptor complex to activate the Ras/MAPK and

The LIFRβ/gp130 pathway is essential for the regulation of astrogliogenesis in the develop‐ ing and adult brain. In cultured cortical precursors, CNTF, LIF and CT-1 all promote astro‐ cyte formation through LIFRβ/gp130 activation [153-155]. Integral to this pathway is signalling via STAT3, as highlighted by the observation that STAT3 activation in neural stem cells induces glial differentiation, while its inhibition promotes a neuronal fate [156, 157]. Also, in neuroepithelial cells, STAT3 activation promotes astrogliogenisis via LIF in‐ duced bone morphogenetic protein 2 expression [158]. In addition to regulating astroglio‐ genesis, STAT3 induction by CNTF was found to be essential in the maintenance of the SGZ

in the regulation of neurogenesis in the developing brain has been suggested [151].

regulatory molecules [146].

248 Trends in Cell Signaling Pathways in Neuronal Fate Decision

**5.1. JAK/STAT signalling**

PI-3K/Akt signalling pathways [49].

[147].

The SOCS family consists of eight members, namely, SOCS1-7 and cytokine-inducible Src homology 2 (SH2) protein (CIS). They are characterised by a central SH2 domain, a C-termi‐ nal SOCS box and a variable N-terminal domain. In addition to these, SOCS1 and SOCS3 also contain a small kinase inhibitory domain. CIS was the first member of this protein fami‐ ly to be cloned. It is also unique to the rest of the SOCS family as a result of its SH2 domain which differs in a few amino acids from most all other known SH2 domains [161].

SOCS expression is induced following activation of the JAK-STAT pathway. This initiates a classic negative feedback loop whereby the SOCS proteins activated by JAK-STAT signal‐ ling now go on to inhibit it. SOCS proteins achieve downregulation of signalling by binding to tyrosine phosphorylated proteins via their SH2 domain. The exact mechanism by which signalling inhibition is achieved varies depending on the SOCS protein in question. For ex‐ ample, SOCS1 and SOCS3 both work to block the kinase activity of activated JAK proteins. In the case of SOCS1, this is achieved by directly binding and blocking access to the activat‐ ed JAK. In the case of SOCS3, this is achieved by its binding to the activated gp130 receptor such that STAT proteins can no longer dock onto the phosphorylated tyrosine residues and be activated by JAK. One mechanism of action for SOCS2 is by blocking STAT access to the activated receptor [162].

SOCS proteins are also able to regulate activity of target proteins, including other SOCS pro‐ teins, through interaction with their SOCS box [163, 164]. Interestingly, SOCS2, SOCS6 and SOCS7 have the potential to interact with all members of the SOCS protein family including themselves [164]. In terms of SOCS2, when expressed at high levels, it is able to inhibit the action of SOCS1 and SOCS3 by targeting them for proteasomal degradation [164]. This has also been proposed as a mechanism for the dual action of SOCS2 on GH signalling as ob‐ served in the overgrowth phenotypes of SOCS2 knockout and overexpressing mice descri‐ bed below [165].

Signalling via the JAK-STAT pathway has an important role in neural precursor prolifera‐ tion and differentiation [153, 166-168]. Following the discovery that SOCS proteins regulate the JAK-STAT pathway, the next obvious step was to examine them for possible roles in the nervous system. In doing so, analysis of the SOCS family gene expression in the developing mouse forebrain brought SOCS2 into the spotlight [168]. The genes SOCS1 – SOCS3 and CIS were found to be expressed at all ages (E10 to P25) with a common peak in expression be‐ tween E14 and P8. However, the level of SOCS2 expression was much higher in comparison. The spatial pattern of SOCS2 expression also distinguished it from the other SOCS genes, with moderate to high levels of expression in neurogenic regions and in newborn neurons. In the adult, SOCS2 was maintained in the CA3 region of the hippocampus and at a moder‐ ate level in the dentate gyrus, compared to other SOCS genes whose expression was not lo‐ calized, if expressed at all under basal conditions. SOCS2 expression was also present in the cerebral cortex and other regions such as the olfactory bulb, forebrain and cerebellum. Inter‐ estingly, SOCS2 was first upregulated at the time of neuronal differentiation, which is be‐ tween the developmental stages E10 and E12, suggesting a role for SOCS2 in neural precursor differentiation [168].

induces SOCS gene expression [179]. JAK2 may also activate STAT1 and STAT3, however this can be cell type specific [180, 181]. One mechanism by which SOCS2 may block STAT5 activation is via its binding to phosphorylated tyrosine residues at the STAT5 binding site

Regulation of Basal and Injury-Induced Fate Decisions of Adult Neural Precursor Cells: Focus on SOCS2 and Related

Signalling Pathways

251

http://dx.doi.org/10.5772/53268

SOCS2 can also regulate signalling via the EGF receptor (EGFR) [175, 176]. The main physio‐ logical target for EGFR is EGF. EGFR primarily activates and signals through the Ras/MAPK pathway [183]. In terms of the neuronal effects of EGF, it has been shown to enhance neurite outgrowth and survival of different populations of cultured neurons [175, 183]. Relevant to this review, it also has an important role in neurogenesis. As described above, in the adult SVZ and dentate gyrus, EGF regulates neural precursor cell proliferation [37]. The impor‐ tance of this role is evident when, in response to brain injury, there is an expansion of neural stem cell numbers in the SVZ as a result of an increased responsiveness to EGF due to EGFR upregulation [184]. Important for SOCS2 interaction, EGF also activates STAT5, a process in‐ volving the Src tyrosine kinase [185-187]. Overexpression of SOCS2 in PC12 cells inhibited this EGF induced STAT5 phosphorylation [176]. The EGFR was also constitutively phos‐ phorylated at the Src binding site, Tyr845, in SOCS2 overexpressing PC12 cells. It was there‐ fore proposed that SOCS2 competitively bound to Tyr845 and blocked its dephosphorylation by the phosphatase SHP2 to allow prolonged Src activation and enhancement of neurite out‐

However, while SOCS2 regulated SVZ-derived neurogenesis in a GH dependent manner during development, in the adult SVZ it appears to regulate neurogenesis via regulation of erythropoietin signalling [188]. Further, the mechanism by which SOCS2 regulates adult hippocampal neurogenesis is different and does not appear to involve GH or erythropoietin, although Epo transiently enhanced SGZ NPC proliferation [189, 190]. Hippocampal neuro‐ genesis was studied under control and voluntary exercise conditions (to enhance basal hip‐ pocampal neurogenesis) in wildtype, SOCS2Tg and GHR-/- mice. Mice of all 3 genotypes had similar basal levels of neurogenesis and equivalently increased neurogenesis in response to exercise at early timepoints (8 days) aimed at measuring extent of NPC proliferation. How‐ ever, at later timepoints (35 days) aimed at examining newborn neuron survival, there was a 50% increase in the survival of adult hippocampal neurons in SOCS2Tg mice, under basal conditions and following voluntary exercise. Additionally, SOCS2Tg mice performed better than wildtype animals in the Morris Water Maze which probes hippocampal-dependent cognition [190]. This was an exciting result, as it identified SOCS2 as a potential therapeutic target that could enhance the survival of newly born neurons following brain injury. How‐ ever, given that GHR-/- mice showed no differences in adult hippocampal neurogenesis compared to wildtype, the mechanism by which SOCS2 promotes survival in this case re‐ mains to be determined. One possible explanation for this increase in neuronal survival in SOCS2Tg mice may be that the enhanced neurite outgrowth observed in SOCS2Tg neurons may aid functional integration into existing circuitry and the consequent maturation and

on the GHR [182].

growth [176].

survival of neurons.


**10th Anniversary of Water**

Special Issue Editor **Arjen Y. Hoekstra†**

MDPI • Basel • Beijing • Wuhan • Barcelona • Belgrade

*Special Issue Editor* Arjen Y. Hoekstra† University of Twente The Netherlands

*Editorial Office* MDPI St. Alban-Anlage 66 4052 Basel, Switzerland

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**5.5 Inflammation**

Inflammation is common to both T1DM and T2DM. However, in T1DM inflammation is upstream involving cellular interactions that release cytokines and fibrinogen [127]. The cytokines and fibrinogen have been found to influence platelet activation independent of hyperglycemia [123, 128]. Since fibrinogen is an acute phase protein

associated with acute inflammatory conditions, its correlation with platelet functions points to the role of inflammation in the modulation platelet response after stimulation.