Figure 5.

A-II amacrine morphology is perturbed in ApoER2 KOs at P7. Dab1 (red) and PKCα (blue) colabeling was performed on wild-type and ApoER2 KO retinas from P7. A–C, Rod bipolar axons extended into the IPL of wild-type retinas where they branched and started to form swollen varicosities in close association with A-II amacrine dendrites. D, E, The density of branched rod bipolar axons is reduced in ApoER2 KOs, paralleled by severely reduced dendritic arborization of A-II amacrine cells. PKCα was highly expressed by A-II amacrine cells in ApoER2 KO but not wild-type retinas. Upon closer magnification of F, a late developing rod bipolar axon can be seen in tight association with A-II amacrine soma. G–L, GlyT-1 was also used as a colabel (green) to visualize changes in A-II amacrine morphology. G–H, An A-II amacrine cell from C was magnified, revealing a dominant layer of dendritic appendages in s5 of a wild-type retina. GlyT-1 not colocalized with Dab1 likely represents synapses belonging to other glycinergic amacrine cells. J–L, In contrast, the A-II amacrine cell asterisked in F had a significant reduction in Dab1/GlyT-1-positive dendrites in s5. Scale bars: F (for A–F), 10 μm; J (for G–L), 5 μm.