Molecular and functional analysis of CIC-5 in idiopathic low-molecular-weight proteinuria

CIC-5在特发性低分子量蛋白尿中的分子和功能分析

• 批准号: 10670703
• 负责人: AIBA Satoru
• 金额: $ 1.86万
• 依托单位: TOHOKU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10670703/
• 关键词: low-molecular-weight protein; renal tubulopathy; chloride ion; genetic disorders; voided tubule cells; cell culture; クロライドチャンネル; 尿細管機能障害; 蛋白尿

Mutations in the CLCN5 gene have been demonstrated in three disorders of hypercalciuric nephrolithiasis, i.e., Dent's disease, X-linked recessive nephrolithiasis, and X-linked recessive hypophosphatemic rickets. Recently, a number of Japanese children with low-molecular-weight proteinuria (LMWP) showing symptoms similar to those shown by patients with Dent's disease in British families have also been reported to have mutations in the CLCN5 gene. The present study examines five unrelated Japanese families with LMWP, two of which lacked any signs other than LMWP, and three of which had several signs other than LMWP, i.e., hypercalciuria, aminoaciduria, hypophosphatemia, and rickets. One nonsense (E118X) and one missense (W22G) mutations were found in three patients in the two families having only LMWP. One genomic deletion including exon 5 to 8 in the CLCN5 gene was found in a patient with hypophosphatemic rickets, and a nonsense mutation (R347X) was found in one patient with LMWP and slight hypercalciuria. No mutation of the exons and exon-intron boundaries in the CLCN5 gene was found in one patient with LMWP, aminoaciduria, and hypokalemia. In addition to the predicted loss of chloride channel function in these nonsense and deletion mutations, the loss of function in the missense mutation W22G was confirmed in the Xenopus oocyte expression system. These results clarified four novel mutations in the CLCN5 genes and additionally suggested that the loss-of-function mutation of the CLCN5 does not necessarily lead to hypercalciuria and nephrocalcinosis in the early stage of the disease, and that LMWP is an early and essential manifestation of disorders of the CLC-5 chloride channel.

CLCN 5基因的突变已经在三种高尿钙肾结石疾病中得到证实，即，登特氏病、X连锁隐性肾结石和X连锁隐性低磷血症佝偻病。最近，一些日本儿童的低分子量蛋白尿（LMWP）表现出类似的症状与英国家庭中的登特氏病患者所表现出的症状也被报道有CLCN 5基因突变。本研究检查了五个不相关的日本LMWP家族，其中两个家族缺乏LMWP以外的任何体征，其中三个家族具有LMWP以外的几个体征，即，高钙尿症、氨基酸尿症、低磷酸盐血症和佝偻病。在两个LMWP家系中的3例患者中发现了1个无义突变（E118 X）和1个错义突变（W22 G）。在1例低磷血症性佝偻病患者中发现CLCN 5基因第5 ~ 8外显子缺失，在1例LMWP伴轻度高钙尿症患者中发现无义突变（R347 X）。在1例LMWP、氨基酸尿和低钾血症患者中未发现CLCN 5基因外显子和外显子-内含子边界突变。除了在这些无义突变和缺失突变中预测的氯离子通道功能丧失之外，错义突变W22 G中的功能丧失在爪蟾卵母细胞表达系统中得到证实。这些结果阐明了CLCN 5基因中的四种新突变，并进一步表明CLCN 5的功能丧失突变不一定导致疾病早期的高钙尿症和肾钙质沉着症，并且LMWP是CLC-5氯离子通道障碍的早期和基本表现。