Roles of homeobox genes in retinal ganglion cell differentiation and axonal guidance

Abstract

Retinal ganglion cells (RGCs) provide the only output of the retina, with their axons projecting to central nervous system targets. The combinatorial roles of homeodomain (HD) and basic helix-loop-helix (bHLH) transcription factors (TFs) determine RGC differentiation. The Class IV POU-domain proteins, BRN3a, BRN3b, and BRN3c, are all expressed in RGC. However, only Brn3b deletion leads to a major defect in RGC differentiation and axonal guidance. Dlx1/Dlx2 double knockout mice have 33% loss of late-born RGCs. Vax2 is restricted to ventral RGC and maintains ventral RGC axonal projections to their target, the medial rostral superior colliculus (SC). Isl1 defines a distinct but overlapping subpopulation of RGCs with Brn3b, whereas Isl2 specifies the contralateral projection of RGC axons. © 2012 Springer Science+Business Media, LLC.