Glial cell fate specification modulated by the bHLH gene Hes5 in mouse retina

Neurons and glial cells differentiate from common precursors. Whereas the gene glial cells missing (gcm) determines the glial fate in Drosophila, current data about the expression patterns suggest that, in mammals, gcm homologues are unlikely to regulate gliogenesis. Here, we found that, in mouse retina, the bHLH gene Hes5 was specifically expressed by differentiating Müller glial cells and that misexpression of Hes5 with recombinant retrovirus significantly increased the population of glial cells at the expense of neurons. Conversely, Hes5-deficient retina showed 30-40% decrease of Müller glial cell number without affecting cell survival. These results indicate that Hes5 modulates glial cell fate specification in mouse retina.