Kirrel (kin of irregular chiasm-1-like) proteins, also known as the NEPH (nephrin-like) family, are type I transmembrane glycoproteins within the immunoglobulin superfamily. Kirrel1 (NEPH1), Kirrel2 (NEPH3, Filtrin, NLG-1) and Kirrel3 (NEPH2, kirre) share 34 - 44% amino acid (aa) identity, and all interact with nephrin, podocin and the adaptor molecule ZO-1 (1, 4). All can be found in podocytes of the kidney glomerulus, and play a role in barrier function in the slit diaphragm. (2-6). Kirrel1 can also be found in central nervous system neurons, pancreas and placenta, Kirrel2 in pancreatic islet beta cells, brain and lymph nodes, and Kirrel3 in the brain and bone marrow, typically at sites where nephrin is also expressed.