Figure 11

The developmental progression of Ptf1a-expressing horizontal and amacrine cells in the retina. Results used to draw this schematic come from this study and [29, 33]. Beginning at 35 hpf, some multipotent progenitors undergo their terminal division and migrate towards their final laminar position (unconstrained mode) over the next 3 to 6 hours. During this migration, Ptf1a:GFP expression is turned on. Once settled at their correct position, processes start extending towards the developing IPL (basally for amacrine cells with somas in the INL, apically for amacrine cells that will be displaced to the ganglion cell layer). Some of these Ptf1a:GFP-expressing cells migrate back apically, reach their final layer, undergo a last division as committed horizontal progenitors and subsequently differentiate as horizontal cells. Processes of differentiating amacrine cells in the INL start extending laterally in the IPL either in the outer or inner half. By 120 hpf, horizontal and amacrine cell types have differentiated and 28 different subtypes of amacrine cells can be distinguished. AC, amacrine cell; GCL, ganglion cell layer; HC, horizontal cell; hpf, hours postfertilization; INBL, inner neuroblastic layer; INL, inner nuclear layer; IPL, inner plexiform layer; ONBL, outer neuroblastic layer; ONL, outer nuclear layer; OPL, outer plexiform layer.