Cell adhesion molecule that plays a role in neuronal self-avoidance. Promotes repulsion between specific neuronal processes of either the same cell or the same subtype of cells (By similarity). Adhesion molecule that promotes lamina-specific synaptic connections in the retina: expressed in specific subsets of interneurons and retinal ganglion cells (RGCs) and promotes synaptic connectivity via homophilic interactions (PubMed:18216854). Homodimer; mediates homophilic interactions to promote cell adhesion. SDK1, SDK2, DSCAM and DSCAML1 are expressed in non-overlapping subsets of interneurons and retinal ganglion cells (RGCs) that form synapses in distinct inner plexiform layer (IPL) sublaminae (PubMed:18216854).