Cis-regulatory analysis of the key developmental gene, Sox10, in neural crest and ear

Abstract

In vertebrates, Sox10 is a transcription factor essential for the formation of neural crest cells and their derivatives as well as placode-derived inner ear structures. At gastrula stages, both presumptive neural crest and placode cells reside at the neural plate border, between the non-neural ectoderm and the neural plate. Despite their common site of origin, these two cell populations have different characteristics. Neural crest cells are a multipotent, stem cell-like population that arises at all axial levels, migrates extensively in the embryo and forms a wide array of derivatives ranging from neurons to melanocytes and cartilage. On the other hand, placode cells are restricted to the cranial region, have limited migratory capacity and contribute only to sensory structures such as the eye, ear, olfactory epithelium and distal portions of the cranial sensory ganglia. Interestingly, I have identified cis-regulatory modules responsible for the regulation of Sox10 in these two different embryonic regions and at different times. Among these modules, I found a downstream novel cis-regulatory region, Sox10E2,that mediates initial Sox10 expression in cranial neural crest cells and otic placode cells. Through a combination of computational analysis, experimental perturbation of putative upstream transcription factors and their binding sites within the Sox10E2 regulatory module, plus chromatin immunoprecipitation, I revealed a set of direct inputs into Sox10E2 regulatory region. The results show that cMyb, Sox9 and Ets1 are responsible for the initial Sox10 expression in delaminating cranial neural crest cells, whereas cMyb, Sox8 and Pea3 regulate Sox10 expression in the otic placode. Analyzing Sox10 regulation through the enhancer Sox10E2 has helped unravel gene regulatory inputs contributing to both neural crest formation and otic placode development. The finding that paralogous factors activate the same regulatory module in these two populations suggests the intriguing possibility of an ancient cooption of regulatory function and/or a common ancestral crest-placode origin.