Figure 15

Proposed model for Vsx2 as a cell fate time regulator. We propose that Vsx2 expressed in progenitors represses genes required for differentiation of multiple lineages, including Vsx1- and Ath5-expressing cells, and possibly also represses itself. Only when Vsx2 is turned off can cells proceed to initially form progenitors that express Vsx1 and later Ath5 (arrows). These cells will continue differentiation in the previously described conserved histogenic order. We show a possible repression of Ath5, the first gene known to be directly involved in neural cell fate during retina development. Our data also support the idea of a repression of horizontal and amacrine fate genes, possibly through Foxn4 (dashed arrow).