Studying the ATOH1 gene regulatory network

Hearing loss due to injury of the sensory hair cells of the inner ear is largely irreversible in mammals. ATOH1, a proneural basic helix loop helix transcription factor is essential for inner ear hair cell differentiation and has garnered particular interest as a potential regeneration tool. Additionally, the transcription factors, POU4F3 and GFI1, are important in maturation and maintenance of inner ear hair cells and compel attention themselves. However, the roles of these transcription factors and their interrelationship in hair cell development and maintenance are not completely understood. In order to define a regulatory relationship between these transcription factors requires further study. We transfected a prosensory inner ear precursor cell line with these transcription factors and investigated the global transcriptome changes through microarray analysis and confirmed with quantitative RT-PCR. Furthermore, we employed a bioinformatic approach to explore the promoter regions of these genes and examined potential biological relationships through the Ingenuity Pathway Analysis software. We demonstrate that the regulatory pathways between Atoh1, Pou4f3 and Gfi1 are indirect and together comprise a larger gene regulatory network rather than a direct sequential cascade. Further evaluation revealed that these transcription factors differentially express genes classified into cell cycle and cell proliferation gene ontology categories. Pou4f3 displayed a potential to regulate multiple genes correlated with apoptosis, through which it may exhibit an important facilitatory function in hair cell maintenance. Finally, we illustrate for the first time the potential ability of Atoh1 and Gfi1 to regulate levels of certain proteins through differential regulation of the Ubc gene and cell cycle-associated binding partners.