Expression of polycystin in mouse metanephros and extra-metanephric tissues

The presence of messenger RNA for the mouse homologue of the polycystic kidney disease 1 gene (PKD1) was demonstrated by reverse transcription- polymerase chain reaction (RT-PCR) methods in mouse embryo messenger RNA. A single locus for the PKD1 gene was detected on mouse chromosome 17 by fluorescent in situ hybridization. Immunoprecipitation of proteins from [³⁵S] methionine-labeled mouse metanephric explants with an anti- polycystin antibody (Pc1) revealed high molecular weight hands, the highest being >400 kDa. Immunoperoxidase staining of mouse embryos with Pc1 revealed expression of polycystin as early as day 8 gestation. The expression was seen in epithelial cells of the ureteric bud, in condensing blastemal cells of the developing metanephros and, subsequently, in cells of the nascent tubules. In addition, Pc1 immunoreactivity was seen in hepatocytes and billary epithelium, cardiac and skeletal muscle, neural tissue, gut, and bronchial epithelium. In post-natal and adult mouse kidney and liver persistent slight to moderate immunoreactivity was observed. Immunofluorescent studies of cultured 13-day mouse metanephroi revealed polycystin expression in ureteric bud epithelium, early glomerular structures (that is, condensates, S-shaped and comma-shaped bodies) and in proximal and distal tubular epithelia. These data indicate that the mouse has a single gene homologous to human PKD1 on chromosome 17, and polycystin is expressed in a variety of tissues during embryonic development.