In conclusion, the L623P mutation in the thiazide-sensitive Na-Cl cotransporter gene is suggested to impair the transporter activity, and to underlie this familial Gitelman's syndrome; Gitelman's syndrome observed in this kindred has been inherited in an autosomal recessive fashion.
Since he had two missense mutations (R261C and L623P) in the thiazide-sensitive Na-Cl cotransporter (TSC) gene (SLC12A3), he was diagnosed as having GS.
These results indicate that the R642C mutation in TSC is critically important for impairment of this cotransporter function and also suggest the necessity of further investigations in the genetic background of Gitelman's syndrome.
Although further in vitro study is required to prove that the mutations are responsible for GS, it is possible that Thr180Lys and Arg642Cys mutations might be common mutations in Japanese GS.
Genetic analysis identified SCN5A H558R polymorphism, which modulates the function of myocardial sodium channel, and SLC12A3 A588V mutation, which causes GS.
While the T180K variation was just a polymorphism, the L849H mutation was confirmed to be a loss-of-function mutation and appears to be responsible for the Gitelman's syndrome.
Genetic analysis evidenced a homozygous mutation (p.Arg399Cys) in the SLC12A3 gene coding for the sodium-chloride cotransporter (NCC), confirming the diagnosis of Gitelman syndrome.
Although further in vitro study is required to prove that the mutations are responsible for GS, it is possible that Thr180Lys and Arg642Cys mutations might be common mutations in Japanese GS.
However, mutation analysis showed that the proband is a compound heterozygote for 2 mutations in SLC12A3: a substitution of serine by leucine at amino acid position 555 (p.Ser555Leu) and a novel guanine to cytosine transition at the 5' splice site of intron 22 (c.2633+1G>C), providing the molecular diagnosis of GS.
Genetic testing showed that both were homozygotes for a novel missense mutation in exon 10 of the SLC12A3 gene [NM_000339.2, c.1276A > T; p.N426Y], which has not previously been reported in the literature in association with GS.
Genetic analysis of the SLC12A3 gene identified two novel missense mutations (c.1919A > G, p.N640S in exon 15; c.2522A > G, p.D841G in exon 21) in the patient with GS.
Since he had two missense mutations (R261C and L623P) in the thiazide-sensitive Na-Cl cotransporter (TSC) gene (SLC12A3), he was diagnosed as having GS.
To better model human GS caused by a specific mutation in the thiazide-sensitive Na(+) -Cl(-) cotransporter (NCC) gene SLC12A3, we generated a nonsense Ncc Ser707X knockin mouse corresponding to human p.Ser710X (c.2135C>A), a recurrent mutation with severe phenotypes in Chinese GS patients.
This case is the first to report a homozygous mutation in the 841th nucleotide of exon 6 on the SLC12A3 gene (p.Trp281Arg), which may cause Gitelman syndrome.
We have investigated the mechanisms by which a novel missense point mutation (c.1181G>A) found in two sisters causes Gitelman's syndrome by impairing the sodium chloride co-transporter (NCC, encoded by SLC12A3 gene) function.