The role of NeuroD as a differentiation factor in the mammalian retina

NeuroD, a vertebrate homolog of Drosophila atonal gene, plays an important role in the differentiation of neuronal precursors (Lee et al., 1995). We h ave investigated whether NeuroD subserves a similar function in mammalian r etinal neurogenesis. Expression of NeuroD is detected in successive stages of retinal neurogenesis and is associated with a differentiating population of retinal cells. The association of NeuroD predominantly with postmitotic precursors in early as well as late neurogenesis suggests that NeuroD expr ession plays an important role in the terminal differentiation of retinal n eurons. This notion is supported by observations that overexpression of Neu roD during late neurogenesis promotes premature differentiation of late-bor n neurons, rod photoreceptors, and bipolar cells, and that NeuroD can inter act specifically with the E-box element in the proximal promoter of the phe notype-specific gene, opsin.