Six3 overexpression rescues the Six3OS knockdown phenotype whereas Six3OS overexpression is not sufficient to rescue the loss of Six3. (A) Six3OS knockdown combined with Six3 overexpression led to a cell type distribution indistinguishable from cells electroporated with control constructs when tested by immunostaining of dissociated electroporated retinal cells. (B) Six3 knockdown combined with Six3OS overexpression led to an increase in Muller glia and a decrease in rod bipolar cells and a decrease in syntaxin (Syn)-positive amacrine cells. GS, glutamine synthetase. (C-E) Section immunohistochemistry of retinas confirm a distribution of GFP-positive cells that is indistinguishable from controls when Six3OS knockdown is combined with Six3 overexpression, while Six3 knockdown and Six3OS overexpression led to a decrease in bipolar cells (F, white arrowheads). GCL, ganglion cell layer; INL, inner nuclear layer; ONL, outer nuclear layer; OS, outer segment.