Idiopathic low molecular weight proteinuria associated with hypercalciuric nephrocalcinosis in Japanese children is due to mutations of the renal chloride channel (CLCN5).

Abstract

The annual urinary screening of Japanese children above 3 yr of age has identified a progressive proximal renal tubular disorder characterized by low molecular weight proteinuria, hypercalciuria, and nephrocalcinosis. The disorder, which has a familial predisposition and occurs predominantly in males, has similarities to three X-linked proximal renal tubular disorders that are due to mutations in the renal chloride channel gene, CLCN5. We have investigated four unrelated Japanese kindreds with this tubulopathy and have identified four different CLCN5 mutations (two nonsense, one missense, and one frameshift). These are predicted to lead to a loss of chloride channel function, and heterologous expression of the missense CLCN5 mutation in Xenopus oocytes demonstrated a 70% reduction in channel activity when compared with the wild-type. In addition, singlestranded conformation polymorphism (SSCP) analysis was found to be a sensitive and specific mutational screening method that detected Ͼ 75% of CLCN5 mutations. Thus, the results of our study expand the spectrum of clinical phenotypes associated with CLCN5 mutations to include this proximal renal tubular disorder of Japanese children. In addition, the mutational screening of CLCN5 by SSCP will help to supplement the clinical evaluation of the annual urinary screening program for this disorder. ( J. Clin. Invest. 1997. 99:967-974.)

Relevance of the D13 Region to the Function of the Skeletal Muscle Chloride Channel, ClC-1

“…By contrast, fully functional, although kinetically slower, versions of rClC-1 are expressed and inserted into the membrane of Sf9 cells, despite lacking the D13 domain or the final 100 amino acids of the carboxyl tail. These results are consistent with previous observations of the naturally occurring myotonic mutant of human ClC-1, R894X (8), and of ClC-5 mutants associated with Dent's disease (10,11). The conclusions from these earlier studies have, however, implicated D13 as an essential functional region (4).…”

“…Reconstitution experiments (4), in which the nonfunctional mutant S720X was restored to functionality by co-expression with either the complementary or an overlapping carboxyl tail peptide, have reinforced this view. Another hint of the importance of D13 is provided by mutations that truncate the kidney chloride channel, ClC-5, before or within D13, these also being nonfunctional when expressed in Xenopus oocytes (10,11).…”

A case of adult Dent disease in Japan with advanced chronic kidney disease

“…Assays were performed using QuickGene DNA whole blood kit S (Fujifilm, Japan). Leukocyte DNA was extracted, and all the exons and exon-intron boundaries were amplified using CLCN5-specific primers via polymerase chain reaction (PCR) amplification, according to previously described methods [5]. The DNA sequence of the PCR products was determined by Taq polymerase cycle sequencing and a semi-automated detection system (ABI 3130xl Genetic Analyzer; Applied Biosystems, Japan).…”

ClC-5 chloride channel and kidney stones: what is the link?

“…Many of them have explored and characterized the mutations responsible for the several variants of XLN (20,21,26,28,30,(56)(57)(58)(59). Very few papers have focused on the physiological role and regulation of this channel (35,47,49).…”

“…Although ClC-5 may have a structure and function pattern similar to that of other members of the family, such studies have not been done on ClC-5. Similar studies are necessary because they could help clarify why different mutations of ClCN5 may result in such different phenotypes (20,21,26,28,30,(56)(57)(58)(59)(60).…”