Loss of TMEM16B from Mpp4 ^−/− photoreceptor synapses. A , B , Retinal sections from wild-type ( A ) and Mpp4 ^−/− mutant ( B ) mice were double-labeled with TMEM16B-7H10 (green) and MPP4 (red) antibodies. Yellow color in the merged wild-type image ( A ) indicates colocalization of TMEM16B and MPP4 in the OPL. Scale bars: 50 μm.