Can we generate new hypotheses about Dent's disease from gene analysis of a mouse model? Experimental Physiology - Symposium Report

In humans, Dent's disease, an X-linked renal tubular disorder, is characterized by low molecular weight proteinuria, aminoaciduria, glycosuria, hyperphosphaturia, hypercalciuria, nephrolithiasis, progressive renal failure and sometimes rickets or osteomalacia. The aetiology of X-linked Dent's disease is established to be caused by mutations of the CLCN5 gene. The protein product of this gene is the voltage-gated chloride-proton exchanger CLC-5. Previous studies by the Johns Hopkins group (Guggino) and the Hamburg group (Jentsch) have established that the Clcn5 knockout mouse recapitulates the renal attributes of Dent's disease. In order to understand the changes in kidney function that accompany the knockout of the Clcn5 gene, we examined gene expression profiles from dissected proximal segment 1 (S1) and segment 2 (S2) tubules of mouse kidneys. Overall, 725 genes are expressed differentially in the proximal tubules of the Dent Clcn5 knockout mouse model compared with those of control wild-type mice. A major finding is the change in the cholesterol synthesis pathway. Some interesting changes also occur in genes encoding transport proteins. One of these transport proteins, the sodium bile cotransporter gene, Slc10a2, has transcripts increased by 17-fold in the Clcn5 knockout mouse. The Clc-3 protein encoded by Clcn3, a chloride-proton exchanger related to Clc-5, has a 1.9-fold increase in transcripts. The Npt2c protein, a proximal tubule sodium phosphate cotransporter encoded by Slc34a3, has a 0.6-fold decrease in the number of transcripts. The sodium-proton exchanger-like protein, Nhe10/sperm, encoded by Slc9a10, has a 0.5-fold decrease in transcript number. These genes are discussed with regard to the possible physiological outcomes of their transcript or protein changes.