Molecular basis of autosomal recessive polycystic kidney disease (ARPKD).

Autosomal recessive polycystic kidney disease (ARPKD) is a serious genetic disease characterized by cystic changes in the collecting ducts of the kidney and bile ducts within the liver. The gene for ARPKD (PKHD1) is located on chromosome 6p12 and encodes a protein called fibrocystin/polyductin (FPC), 1 of many proteins that are normally present at the primary cilia of the renal tubules and intrahepatic bile ducts. The severity of the clinical disease depends on the type of genetic mutations. Although exact function of FPC is not fully known, it is generally felt that like many of the other ciliary proteins, it plays a vital role in maintaining the structural integrity of organs such as kidney and liver, by modulating important cellular functions, including proliferation, secretion, apoptosis, and terminal differentiation. FPC probably works in conjunction with cellular proteins involved in autosomal dominant polycystic kidney disease that is, polycystin-1 and polycystin-2, which are also located in the primary cilia. Genetic abnormalities in PKHD1 may result in structural and functional abnormalities of FPC, leading to cystic phenotype.