Mutations of CLCN5 in Japanese children with idiopathic low molecular weight proteinuria, hypercalciuria and nephrocalcinosis.
Akuta N., Lloyd SE., Igarashi T., Shiraga H., Matsuyama T., Yokoro S., Cox JP., Thakker RV.
The annual urinary screening of Japanese children above three years of age has identified a progressive renal tubular disorder characterized by low molecular weight proteinuria, hypercalciuria and nephrocalcinosis. The disorder has been observed in over 60 patients and has a familial predisposition. Mutations of a renal chloride channel gene, CLCN5, have been reported in four such families, and we have undertaken studies in additional patients from 10 unrelated, non-consanguineous Japanese families to further characterize such CLCN5 mutations and to ascertain their prevalence. CLCN5 abnormalities we identified in 7 of the 10 unrelated patients and consisted of 5 mutations (2 nonsense, 1 frameshift and 2 missense), 1 deletion and 1 silent polymorphism. A clustering of these mutations in CLCN5 exons 8 and 10 was observed. Over 80% of the CLCN5 mutations could be readily detected by single stranded conformational polymorphism (SSCP) analysis, thereby providing a useful mutation screening method. Our results, which indicate that over 70% of Japanese patients with this renal tubulopathy have CLCN5 mutations, will help in the genetic and clinical evaluation of children at risk from this disorder.