Provides, together with MAGI1, an adhesion machinery at tight junctions, which may regulate the permeability of kidney glomerulus and small intestinal epithelial cells. Mediates calcium-independent homophilic cell adhesion. In testis, it may function as a cell adhesion molecule rather than a tight-junction protein. It may participate in the adhesion between spermatogonia-spermatogonia, spermatogonia-Sertoli cells, and Sertoli cells-Sertoli cells. Interacts with MAGI1 at tight junctions, forms a tripartite complex with NPHS1 (By similarity). Interacts with LNX1 isoform 2 via its PDZ 2 domain, it may also interact with other isoforms containing this domain. Localized to kidney glomeruli and small intestinal epithelial cells. In kidney glomeruli, it is localized at slit diaphragm. Also found in spermatogonia, gonocytes, hematopoietic stem cells and Sertoli cells. N-glycosylated. No visible phenotype. Belongs to the immunoglobulin superfamily.