Nephrin is the protein product of the NPHS1 gene. It is a transmembrane protein of the immunoglobulin superfamily, containing 1241 amino acids. Nephrin is produced by glomerular podocytes, and expressed in the visceral epithelial cells, suggesting that it plays an important role in the development or maintenance of the glomerular filtration barrier. Defects in this protein are the cause of nephrotic syndrome type 1 (NPHS1), an autosomal recessive disease characterized by proteinuria, hypoalbuminemia, hyperlipidemia, and edema.

Two common mutations in the NPHS1 gene have been identified in the Finnish population in connection with NPHS1; the Fin-major and the Fin-minor. The Fin-major mutation results in a frameshift and a stop codon in exon 2 and a truncated protein of only 90 amino acids, while the Fin-minor mutation is a nonsense mutation in exon 26 and leads to a truncated 1109-residue protein. Insertions, deletions, and nonsense and missense mutations in this gene have been identified in non-Finnish patients.