A comprehensive study of c-Kit-expressing amacrine cells in the mammalian retina

Amacrine cells assemble complex circuits in the inner retina, where they integrate, modulate, and relay spatial and temporal information to retinal ganglion cells. Nevertheless, their organization and functional diversity are still not fully understood. In this study, we identify a distinct group of amacrine cells that express the stem cell factor receptor-c-Kit. Using combined techniques of anti-CD117 (c-Kit) immunolabeling, confocal imaging, and computational algorithms, we characterize the morphological features and spatial distribution of the c-Kit-expressing amacrine cells. Our results show that c-Kit-expressing amacrine cells are GABA-positive neurons with medium to wide dendritic fields that stratify within the specific strata in both ON and OFF sublaminae of the inner plexiform layer (IPL). The density recovery profile of c-Kit cells reveals regulated intercellular spacing, supporting the notion that they represent a single amacrine subtype with significant variation in their dendritic structures. Notably, a subset of these cells also bears ascending processes projecting into the outer plexiform layer (OPL). This distinct anatomical feature raises the possibility that c-Kit-expressing amacrine cells contribute to a long-range circuit across retinal layers and participate in a novel feedback pathway. Further analysis demonstrates that c-Kit-expressing amacrine cells are distinct from AII, starburst, nGnG, vGluT3-positive, VIP-positive, and dopaminergic amacrine cells. Our findings provide a new insight into the cellular diversity of amacrine cells and suggest a previously unrecognized functional role for c-Kit-expressing amacrine cells in the mammalian retina.