NPHS1 and congenital nephrotic syndrome, Finnish type: The best-studied SD protein is Nephrin (gene NPHS1), and more than 250 Nephrin mutations have been linked to congenital nephrotic syndrome of the Finnish type (CNF), an inherited form of steroid-resistant nephrotic syndrome (SRNS) leading to severe proteinuria and renal failure (Kestilä et al, 1998; Martin & Jones, 2018).