Fig. 5.

Blimp1 overexpression increases photoreceptor and decreases bipolar cell fate choice. (A-D) P1 retinas were electroporated in vivo with GFP control (A,B) or Blimp1-GFP (C,D) expression vectors and tissue collected at P5. (A,C) Transfected regions of control (A) and Blimp1-GFP (C) retinas stained for GFP (green) and Otx2 (red). The bright, elongated nuclei (termed Otx2⁺⁺) represent bipolars and undifferentiated photoreceptors and bipolars (arrows), whereas the faint, small nuclei (Otx2⁺) mark photoreceptors (arrowheads). (B,D) Definitive bipolars in GFP control (B) or Blimp1-GFP (D) transfected retinas were labeled for Chx10 (red) (arrows). Arrowheads mark photoreceptors. (E) Relative frequency of cell fates observed in Blimp1-GFP-transfected cells normalized to control (1.0). At P5, Blimp1-GFP cells were more likely to be photoreceptors and less likely to be bipolar cells compared with controls. Error bars indicate the s.d. ^*, P<0.05; ^**, P<0.01; unpaired two-tailed t-tests. Scale bars: 50 μm, except 5 μm for insets.