Fig. 9.

RGC birthdates in transgenic, Math5 KO and rescued animals. Embryos with the four indicated genotypes were exposed to a single pulse of EdU at E11 and E12, E13.5, E15.5 or E17.5, and are compared as littermates. (A–D) GCL confocal views of P1 birthdated retinal flatmounts, stained for Brn3a (green) and EdU (magenta). (E) RGC birthdating curves for each genotype. No Brn3a+ RGC births were detected in any genotype after E17. The overall number of RGC births is substantially reduced in Math5 KO and Crx>Math5 Tg (Tg) rescued mice. (F) Normalized RGC birthdating curves for each genotype. Because virtually all RGCs are born between E11 and E17, the total number of RGCs was summed across the 4 time points for each genotype, and the RGC birth fraction at each time is plotted relative to this total. The normalized curves are quite similar. However, very few, if any, Brn3a+ RGCs were born during early neurogenesis (E11–E12) in Math5 knockout (KO) or rescued (Tg; Math5 KO) mice. In the rescued mice, a larger fraction of RGCs were born during mid-gestation (E15.5). (G) Brn3a+ RGC density jitter plots for each genotype. Each data point represents a single eye. The Crx>Math5 transgene (Tg) partially rescues the RGC deficiency in Math5 KO mice, which have significantly more Brn3a+ RGCs than Math5 KO controls, although this effect is variable. The Crx>Math5 Tg does not significantly affect RGC density in heterozygotes. Scale bar, 50 µm.