Nephrocystin-4 (NPHP4), also known as nephroretinin, is a component of the nephronophthisis (NPHP) module which is part of the transition zone (TZ) of the cilia. NPHP4 forms complexes with alpha-tubulin, NPHP1 and RPGRIP1. The interaction with NPHP1 is crucial for cell-cell and cell-matrix adhesion signaling. Mutations in NPHP4 have been shown to cause nephronophthisis (NPHP), an autosomal recessive cause of kidney failure and earlier stages of chronic kidney disease among adults.
Jiyao W et al.(2023). "The conserved domain database in 2023.",