slc4a2b gene mutation leads to HC apoptosis. The control zebrafish, Tg(Brn3c:mGFP) (A), and the mutant zebrafish, Tg(Brn3c:mGFP);slc4a2bmut (B), were used for the apoptosis assay. Here, the anti-cleaved caspase-3 antibody was used to detect the apoptotic cells. Scale bar = 20 μm.