Zac1+m/- retinae lose amacrine cell feedback inhibition. (a) Schematic of aggregation assay protocol. (b-j) Immunolabeling of dissociated cell pellets with Pax6 (red (c,d,f,g,i,j)), BrdU (green (b,d,e,g,h,j)) and merged image with DAPI (blue (d,g,j)). E14.5 progenitors cultured alone (b-d) or with E18.5 wild-type (e-g) or Zac1+m/- (h-j) retinal cells. Arrowheads mark Pax6/BrdU double+ nuclei (d,g,j). (k) Percentage of BrdU+ E14.5 cells that differentiated into Pax6+ amacrine cells when cultured alone (black bar; 1,085 BrdU/Pax6 double+/2,892 BrdU+) or with E18.5 wild-type (grey bar; 853 BrdU/Pax6 double+/3,215 BrdU+) or Zac1+m/- (white bar; 2,559 BrdU/Pax6 double+/7,196 BrdU+) retinal cells. n indicates number of individual retinal aggregates quantified.