Fig. 5.

Working model for Xbsx function in cell proliferation and differentiation of photoreceptor precursors. (A) Schematic summary of the relation between Xbsx expression and pineal cell proliferation in WT and manipulated embryos. (B) Model of action for Xbsx. The pink cell represents the common progenitor of projection neurons and photoreceptors. It is assumed that photoreceptor precursors undergo a limited number of asymmetrical cell divisions. Xbsx knockdown prevents cell cycle exit of photoreceptor precursors that eventually undergo apoptosis. Xbsx overexpression increases cell cycle exit of photoreceptor precursors and promotes their differentiation.