Mutations of the polycystic kidney and hepatic disease 1 (PKHD1) gene have been 
shown to cause autosomal recessive polycystic kidney disease (ARPKD), but the 
cellular functions of the gene product (PKHD1) remain uncharacterized. To 
illuminate its properties, the spatial and temporal expression patterns of PKHD1 
were determined in mouse, rat, and human tissues by using polyclonal Abs and 
mAbs recognizing various specific regions of the gene product. During 
embryogenesis, PKHD1 is widely expressed in epithelial derivatives, including 
neural tubules, gut, pulmonary bronchi, and hepatic cells. In the kidneys of the 
pck rats, the rat model of which is genetically homologous to human ARPKD, the 
level of PKHD1 was significantly reduced but not completely absent. In cultured 
renal cells, the PKHD1 gene product colocalized with polycystin-2, the gene 
product of autosomal dominant polycystic disease type 2, at the basal bodies of 
primary cilia. Immunoreactive PKHD1 localized predominantly at the apical domain 
of polarized epithelial cells, suggesting it may be involved in the 
tubulogenesis and/or maintenance of duct-lumen architecture. Reduced PKHD1 
levels in pck rat kidneys and its colocalization with polycystins may underlie 
the pathogenic basis for cystogenesis in polycystic kidney diseases.