rax, hes1, and notch1 promote the formation of Muller glia by postnatal retinal progenitor cells

We are interested in the mechanisms of glial cell development in the verteb rate central nervous system. We have identified genes that can direct the f ormation of glia in the retina, rax, a homeobox gene, Hes1, a basic helix-l oop-helix gene, and notch1, a transmembrane receptor gene, are expressed in retinal progenitor cells, downregulated in differentiated neurons, and exp ressed in Muller glia. Retroviral transduction of any of these genes result ed in expression of glial markers. In contrast, misexpression of a dominant -negative Hes1 gene reduced the number of glia. Cotransfection of rax with reporter constructs containing the Hes1 or notch1 regulatory regions led to the upregulation of reporter transcription. These data suggest a regulator y heirarchy that controls the formation of glia at the expense of neurons.