Elevated proto-oncogene expression in polycystic kidneys of the C57BL/6J (cpk) mouse.

Polycystic kidney disease in the C57BL/6J (cpk) mouse is an autosomal recessive disorder which leads to the rapid development of renal cysts and kidney failure during the first 3 to 4 postnatal weeks. Previously, we showed that the cystic kidneys of affected mice have abnormally elevated levels of c-myc mRNA. In the study presented here, it is shown that mRNAs for the proto-oncogenes c-fos and c-Kiras, as well as c-myc, are markedly elevated in cystic kidneys, suggesting that there is a more general abnormality in gene expression associated with the disease. It is also evident that there are two stages to this abnormal proto-oncogene expression. In the first stage, which occurs up through the second postnatal week, there are modest increases in proto-oncogene mRNA which parallel the increased cell proliferation that accompanies cyst growth at this time. In the second stage, which occurs after the second postnatal week, there are markedly elevated levels of proto-oncogene mRNA that are seen at a time when cell proliferation is declining. The development of this latter stage suggests either that there is a fundamental abnormality intrinsic to polycystic kidneys that leads to uncontrolled proto-oncogene expression later in disease progression or that there is a secondary response in the kidney to the progressive renal failure.