a potential cellular injury and anti-aging treatment. cochlea the retinoblastoma protein is involved in the growth and development of mammalian hair cells of the cochlea, and appears to be related to the cells' inability to regenerate. embryonic hair cells require prb, among other important proteins, to exit the cell-cycle and stop dividing, which allows maturation of the auditory system. once wild-type mammals have reached adulthood, their cochlear hair cells become incapable of proliferation. in studies where the gene for prb is deleted in mice cochlea, hair cells continue to proliferate in early adulthood. though this may seem to be a positive development, prb-knockdown mice tend to develop severe hearing loss due to degeneration of the organ of corti. for this reason, prb seems to be instrumental for completing the development of mammalian hair cells and keeping them alive. however, it is clear that without prb, hair cells have the ability to proliferate, which is why prb is known as a tumor suppressor. temporarily and precisely turning off prb in adult mammals with damaged hair cells may lead to propagation and therefore successful regeneration. suppressing function of the retinoblastoma protein in the adult rat cochlea has been found to cause proliferation of supporting cells and hair cells. prb can be downregulated by activating the sonic hedgehog pathway, which phosphorylates the proteins and reduces gene transcription. neurons disrupting prb expression in vitro, either by gene deletion or knockdown of prb short interfering rna, causes dendrites to branch out farther. in addition, schwann cells, which provide essential support for the survival of neurons, travel with the neurites, extending farther than normal. the inhibition of prb supports the continued growth of nerve cells. interactions prb is known to interact with more than 300 proteins, some of which are listed below: abl gene androgen receptor apoptosis-antagonizing transcription factor arid4a aryl hydrocarbon receptor brca1 brf1 c-jun c-raf cdk9 cutl1 cyclin a1 cyclin d1 cyclin t2 dnmt1 e2f1 e2f2, e4f1 eid1 enc1 frk hbp1 hdac1 hdac3 histone deacetylase 2 insulin jarid1a large tumor antigen lin9 mcm7 morf4l1 mrfap1, myod ncoa6 pa2g4 peroxisome proliferator-activated receptor gamma pik3r3 plasminogen activator inhibitor-2 polymerase (dna directed), alpha 1 prdm2 prkra prohibitin promyelocytic leukemia protein rbbp4 rbbp7 rbbp8 rbbp9 snapc1 skp2 snapc3 snw1 suv39h1 taf1 thoc1 trap1 trip11 ubtf usp4. detection several methods for detecting the rb1 gene mutations have been developed including a method that can detect large deletions that correlate with advanced stage retinoblastoma. overview of signal transduction pathways involved in apoptosis.