Nozu Kandai, Fu Xue Jun, Nakanishi Koichi, Yoshikawa Norishige, Kaito Hiroshi, Kanda Kyoko, Krol Rafal Przybyslaw, Miyashita Ritsuko, Kamitsuji Hidekazu, Kanda Shoichiro, Hayashi Yoshiki, Satomura Kenichi, Shimizu Nobuhiko, Iijima Kazumoto, Matsuo Masafumi
Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Hyogo, 6500017, Japan.
Pediatr Res. 2007 Sep;62(3):364-9. doi: 10.1203/PDR.0b013e318123fb90.
Type III Bartter syndrome (BS) (OMIM607364) is caused by mutations in the basolateral chloride channel CIC-Kb gene (CLCNKB). The CLCNKB gene is sometimes reported as having a large deletion mutation, but all cases reported previously were large homozygous deletions and a large heterozygous deletion is impossible to detect by direct sequencing. This report concerns a genetic analysis of five Japanese patients with type III BS. To identify the mutations, we used polymerase chain reaction (PCR) and direct sequencing. To detect large heterozygous deletion mutations of the CLCNKB gene, we conducted semiquantitative PCR amplification using capillary electrophoresis. The result was that four mutations were identified, comprising one novel 2-bp deletion mutation, an entire heterozygous deletion, and a heterozygous deletion mutation of exons 1 and 2. The nonsense mutation W610X was detected in all patients, and this mutation is likely to constitute a founder effect in Japan. Capillary electrophoresis is a new method and extremely useful for detecting large heterozygous deletions, and should be used to examine type III BS cases in whom only a heterozygous mutation has been detected by direct sequencing. This is the first report to identify large heterozygous deletion mutations in the CLCNKB gene in patients with type III BS.
III型巴特综合征（BS）（OMIM607364）由基底外侧氯通道CIC-Kb基因（CLCNKB）突变引起。CLCNKB基因有时报道存在大片段缺失突变，但此前报道的所有病例均为大片段纯合缺失，大片段杂合缺失无法通过直接测序检测到。本报告涉及5例日本III型BS患者的基因分析。为鉴定突变，我们采用聚合酶链反应（PCR）和直接测序。为检测CLCNKB基因的大片段杂合缺失突变，我们使用毛细管电泳进行半定量PCR扩增。结果鉴定出4种突变，包括1种新的2碱基缺失突变、1种完全杂合缺失以及外显子1和2的杂合缺失突变。在所有患者中均检测到无义突变W610X，该突变在日本可能构成奠基者效应。毛细管电泳是一种检测大片段杂合缺失的新方法且极为有用，应用于直接测序仅检测到杂合突变的III型BS病例的检查。这是首篇报道在III型BS患者中鉴定出CLCNKB基因大片段杂合缺失突变的文章。
