Transcriptional and functional analyses of SLC12A3 mutations: new clues for the pathogenesis of Gitelman syndrome.
Gitelman syndrome (GS) is a recessive salt-losing tubulopathy that is caused by mutations in the SLC12A3 gene that encodes the sodium-chloride co-transporter (NCC). GS is characterized by significant inter- and intrafamilial phenotype variability, with early onset and/or severe clinical manifestations in some patients. No correlations between the disease variability and the position/nature of SLC12A3 mutations have been investigated thus far. In this study, extensive mutational analyses of SLC12A3 were performed in 27 patients with GS, including genomic DNA sequencing, multiplex ligation-dependent probe amplification, cDNA analysis, and quantification of allele-specific transcripts, in parallel with functional analyses in Xenopus laevis oocytes and detailed phenotyping. Twenty-six SLC12A3 mutations were identified in 25 patients with GS, including eight novel (detection rate 80%). Transcript analysis demonstrated that splicing mutations of SLC12A3 lead to frameshifted mRNA subject to degradation by nonsense-mediated decay. Heterologous expression documented a novel class of NCC mutants with defective intrinsic transport activity. A subgroup of patients presented with early onset, growth retardation, and/or detrimental manifestations, confirming the potential severity of GS. The mutations that were associated with a severe presentation were the combination at least for one allele of a missplicing resulting in a truncated transcript that was downregulated by nonsense-mediated decay or a nonfunctional, cell surface-absent mutant. The most recurrent mutation on the second allele was a newly described NCC mutant that affected the functional properties of the co-transporter. These data suggest that the nature/position of SLC12A3 mutation, combined with male gender, is a determinant factor in the severity of GS and provide new insights in the underlying pathogenic mechanisms of the disease.
Riveira-Munoz
Eva
E
Division of Nephrology, Université Catholique de Louvain Medical School, Brussels, Belgium.
Chang
Qing
Q
Godefroid
Nathalie
N
Hoenderop
Joost G
JG
Bindels
René J
RJ
Dahan
Karin
K
Devuyst
Olivier
O
D000818:Animals; D018076:DNA, Complementary / Q000737:chemistry; D005260:Female; D005838:Genotype; D053579:Gitelman Syndrome / Q000209:etiology* / Q000235:genetics; D006801:Humans; D009154:Mutation; D010641:Phenotype; D012333:RNA, Messenger / Q000032:analysis; D011955:Receptors, Drug / Q000235:genetics* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D064486:Solute Carrier Family 12, Member 3; D027981:Symporters / Q000235:genetics* / Q000502:physiology; D014158:Transcription, Genetic; D014981:Xenopus
D018076:DNA, Complementary; D012333:RNA, Messenger; D011955:Receptors, Drug; C578874:SLC12A3 protein, human; D064486:Solute Carrier Family 12, Member 3; D027981:Symporters