title: A deep intronic mutation in the SLC12A3 gene leads to Gitelman syndrome.
abstract: Many mutations have been detected in the SLC12A3 gene of Gitelman syndrome (GS, OMIM 263800) patients. In previous studies, only one mutant allele was detected in approximately 20 to 41% of patients with GS; however, the exact reason for the nonidentification has not been established. In this study, we used RT-PCR using mRNA to investigate for the first time transcript abnormalities caused by deep intronic mutation. Direct sequencing analysis of leukocyte DNA identified one base insertion in exon 6 (c.818_819insG), but no mutation was detected in another allele. We analyzed RNA extracted from leukocytes and urine sediments and detected unknown sequence containing 238bp between exons 13 and 14. The genomic DNA analysis of intron 13 revealed a single-base substitution (c.1670-191C>T) that creates a new donor splice site within the intron resulting in the inclusion of a novel cryptic exon in mRNA. This is the first report of creation of a splice site by a deep intronic single-nucleotide change in GS and the first report to detect the onset mechanism in a patient with GS and missing mutation in one allele. This molecular onset mechanism may partly explain the poor success rate of mutation detection in both alleles of patients with GS.
authors: Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan. nozu@med.kobe-u.ac.jp
authors: Kandai
authors: K
authors: Nozu
authors: Kazumoto
authors: K
authors: Iijima
authors: Yoshimi
authors: Y
authors: Nozu
authors: Ei
authors: E
authors: Ikegami
authors: Takehide
authors: T
authors: Imai
authors: Xue Jun
authors: XJ
authors: Fu
authors: Hiroshi
authors: H
authors: Kaito
authors: Koichi
authors: K
authors: Nakanishi
authors: Norishige
authors: N
authors: Yoshikawa
authors: Masafumi
authors: M
authors: Matsuo
mesh_terms: D000483:Alleles; D001483:Base Sequence; D002648:Child; D004252:DNA Mutational Analysis; D005091:Exons; D005260:Female; D053579:Gitelman Syndrome / Q000235:genetics*; D006801:Humans; D007438:Introns; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D012333:RNA, Messenger / Q000378:metabolism; D011955:Receptors, Drug / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D064486:Solute Carrier Family 12, Member 3; D027981:Symporters / Q000235:genetics*
chemical_list: D012333:RNA, Messenger; D011955:Receptors, Drug; C578874:SLC12A3 protein, human; D064486:Solute Carrier Family 12, Member 3; D027981:Symporters