Ptf1a overexpression leads to enhanced proportions of GABAergic horizontal and displaced amacrine cells. Analysis of GABAergic cell proportions among GFP-positive horizontal and amacrine transfected cells in stage 40/41 retinas, following Ptf1a-VP16 lipofection. (A-D) Quantification of GABA-positive cells in the horizontal, amacrine and ganglion cell layers as indicated. Values are given as mean +/- s.e.m. p < 0.001 (***) (binomial test). (E-P) Typical sections of retinas lipofected with gap-GFP alone (E-G, K-M) or gap-GFP plus Ptf1a-VP16 (H-J, N-P), immunostained with an anti-GABA antibody. Arrows in E-G and K-M point to examples of gap-GFP-transfected GABA-negative horizontal and ganglion cell, respectively, in control retinas. Arrows in H-J and N-P point to GABA-positive horizontal and displaced amacrine cells, respectively, in gap-GFP plus Ptf1a-VP16 lipofected retinas. Ctrl: control; HCL: horizontal cell layer; ACL: amacrine cell layer; GCL: ganglion cell layer; INL: inner nuclear layer. Scale Bar represents 30 μm.