Figure 4: Excess ganglion cells in Rorb^1g/1g mice.

(a) Normal numbers of BrdU⁺ proliferating cells were detected in the retina in 1g/1g mice 1 h after a pulse delivery of BrdU. Graph of BrdU⁺ cell counts at E12.5 and P1 shows no differences between +/+ and 1g/1g mice; mean±s.d.; P>0.8. Counts represent BrdU⁺ cells per 150 μm length of retina, determined on 10 μm thick cryosections. Scale bar, 30 μm in all panels. (b) Immunostaining for Brn3a⁺ ganglion cells (purple) in retinal sections at P3. Sections were co-stained for activated caspase 3 (turquoise), a marker of apoptotic cells. Arrows, double-labelled cells in 1g/1g mice, which were rarely observed in +/+ mice. (c) The postnatal decline in excess Brn3a⁺ cells correlated with increased cell death rates in 1g/1g mice. Left, counts of Brn3a⁺ cells per 150 μm length of retina in 10 μm thick sections. For +/+ and 1g/1g differences at E18.5, P3 and P7, P<0.001. Right, counts of caspase 3⁺ cells per section; mean±s.d.; *P<0.001. Statistical analyses were performed using Student’s t-test.