EXPRESSION OF POLYCYSTIN IN MOUSE METANEPHROS AND EXTRA-METANEPHRIC TISSUES

The presence of messenger RNA for the mouse homologue of the polycysti c kidney disease 1 gene (PKD1) was demonstrated by reverse transcripti on-polymerase chain reaction (RT-PCR) methods in mouse embryo messenge r RNA. A single locus for the PKD1 gene was detected on mouse chromoso me 17 by fluorescent in situ hybridization. Immunoprecipitation of pro teins from [S-35] methionine-labeled mouse metanephric explants with a n anti-polycystin antibody (Pc1) revealed high molecular weight bands, the highest being > 400 kDa. Immunoperoxidase staining of mouse embry os with Pc1 revealed expression of polycystin as early as day 8 gestat ion. The expression was seen in epithelial cells of the ureteric bud, in condensing blastemal cells of the developing metanephros and, subse quently, in cells of the nascent tubules. In addition, Pc1 immunoreact ivity was seen in hepatocytes and biliary epithelium, cardiac and skel etal muscle, neural tissue, gut, and bronchial epithelium. In post-nat al and adult mouse kidney and liver persistent slight to moderate immu noreactivity was observed. Immunofluorescent studies of cultured 13-da y mouse metanephroi revealed polycystin expression in ureteric bud epi thelium, early glomerular structures (that is, condensates, S-shaped a nd comma-shaped bodies) and in proximal and distal tubular epithelia. These data indicate that the mouse has a single gene homologous to hum an PKD1 on chromosome 17, and polycystin is expressed in a variety of tissues during embryonic development.