Nephrin is a protein necessary for the proper functioning of the renal filtration barrier. The renal filtration barrier consists of fenestrated endothelial cells, the glomerular basement membrane, and thepodocytes of epithelial cells. Nephrin is a transmembrane protein that is a structural component of the slit diaphragm. They are present on the tips of the podocytes and maintain the normal relationship between the basement membrane and the podocytes of the epithelial cells.A defect in the gene for nephrin, NPHS1, is associated with congenital nephrotic syndrome of the Finnish typeand causes massive amounts of protein to be leaked into the urine, or proteinuria. Nephrin is also required for cardiovascular development.