May 3, 2018

CURE Discovery: Genetic Research Finds Potential Alternatives to Brain Surgery for Children with Cortical Dysplasia

A Potential Alternative is Already in Clinical Trial

Recent research by CURE grantee Dr. Jeong Ho Lee of the Korea Advanced Institute of Science and Technology has shed important light on the genetic mutations that lead to focal cortical dysplasia, a severe form of pediatric epilepsy that inadequately responds to available treatment options. Genetic mutations were found in the brain tissue of individuals affected by a particular subtype of focal cortical dysplasia (focal cortical dysplasia type II) that is characterized by brain abnormalities, leading to seizures and epilepsy.

Conventional genetic testing methods to identify genetic mutations in those with epilepsy often use blood or saliva from patients. However, these latest results from Dr. Lee and his team suggest that certain epilepsy-related gene mutations may only be detectable when brain tissue is analyzed.

Brain-Only Mutations in Genes that Cause Focal Cortical Dysplasia

By comparing blood and saliva samples to samples of brain tissue from a group of 40 individuals who had previously undergone brain surgery for focal cortical dysplasia type II, Dr. Lee and his team found that a significant number of these individuals (12.5%) had brain-only mutations in genes TSC1 and TSC2. Together with the previous pioneering work of his team to identify brain-only mutations in the MTOR gene in individuals with focal cortical dysplasia type II, they revealed that brain-only mutations in genes within the mTOR brain signaling pathway (including the genes TSC1, TSC2 and MTOR) are found in up to 30% of individuals with focal cortical dysplasia. The fact that these mutations were found only in the brain means that these mutations would be undetectable by conventional genetic testing methods, suggesting that investigation of brain-only mutations should be explored to a greater extent.

In addition to identifying brain-only mutations leading to focal cortical dysplasia, Dr. Lee and his team also addressed the current lack of adequate animal models to better study the disorder. The team was able to successfully recreate the brain-only mutations in genes TSC1 and TSC2 in developing mice, providing a much-needed animal model for further examination of the ways in which gene mutations can lead to focal cortical dysplasia type II.

Clinical Trials for the Treatment of Focal Cortical Dysplasia

Furthermore, the team provided evidence that mTOR inhibitors, such as rapamycin or everolimus, are promising anti-epileptic drugs for the treatment of focal cortical dysplasia. In fact, everolimus is currently under phase II clinical trial for the treatment of focal cortical dysplasia.

As noted by Dr. Lee, because focal cortical dysplasia is a drug-resistant epilepsy, many children with the disorder require invasive brain surgery as treatment. However, even in cases where surgery is performed, up to 40% of these children may still have seizures. By identifying genes associated with focal cortical dysplasia as well as creating a new way of studying the genetic mechanisms behind the disorder, Dr. Lee and his team have made progress towards the creation of novel, non-surgical targets at which to aim treatments for this devastating form of drug-resistant childhood epilepsy.

[1] Lim et al. Somatic mutations in TSC1 and TSC2 cause focal cortical dysplasia. Am J Human Genet 2017; 100(3):454-472.
[2] Guerrini et al. Diagnostic methods and treatment options for focal cortical dysplasia. Epilepsia 2015; 56(11):1669-86.
[3] Gaitanis and Donahue. Focal cortical dysplasia. Ped Neurol 2013; 49:79-87.
[4] Poduri et al. Genetic testing in the epilepsies – developments and dilemmas. Nat Rev Neurol 2014; 10(5):293-299.
[5] Lim et al. Brain somatic mutations in MTOR cause focal cortical dysplasia type II leading to intractable epilepsy. Nat Med 2015; 21(4):395-400.

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