Figure 8: Proposed role for RORβ1 in amacrine and horizontal cell differentiation.

It is proposed that RORβ1 and Foxn4 in progenitor cells cooperatively promote commitment to amacrine and horizontal cell fates by synergistic induction of Ptf1a. Ptf1a is transiently induced in post-mitotic precursors and consolidates the fates of both classes of interneurons. Many factors (not shown) contribute to the subsequent terminal differentiation of horizontal and amacrine cell sub-lineages, indicated here according to main neurotransmitter types (GABA, glycine, acetyl choline, dopamine, glutamate). Relative timing of expression of RORβ1, Foxn4 and Ptf1a is indicated on the right: Foxn4 is in dividing progenitors, Ptf1a in post-mitotic precursors and RORβ1 in both progenitors and precursors.