In 1994, the autosomal recessive polycystic kidney disease gene (PKDHD1) was localized to the short arm of chromosome 6.[6] Fibrocystin/polyductin, a protein encoded by PKDHD1, is expressed on the cilia of renal and bile duct epithelial cells and is thought to be crucial in maintaining the normal tubular architecture of renal tubules and bile ducts. However, the precise function of this protein has yet to be completely studied or understood. The protein strengthens the theory that the primary defect in autosomal recessive polycystic kidney disease is linked to ciliary dysfunction