Presence and significance of a R110W mutation in the DNA-binding domain of GCM2 gene in patients with isolated hypoparathyroidism and their family members.
OBJECTIVE
Glial cells missing 2 (GCM2) gene encodes a parathyroid-specific transcription factor. We assessed GCM2 gene sequence in patients with isolated hypoparathyroidism (IH).


METHODS
Case-control study.


METHODS
Complete DNA sequencing of the GCM2 gene including its exons, promoter, and 5' and 3' UTRs was performed in 24/101 patients with IH. PCR-restriction fragment length polymorphism was used to detect a novel R110W mutation in all 101 IH patients and 655 healthy controls. Significance of the mutation was assessed by electrophoretic mobility shift assay (EMSA) and nuclear localization on transfection.


RESULTS
A heterozygous R110W mutation was present in DNA-binding domain in 11/101 patients (10.9%) and absent in 655 controls (P<10(-7)). Four of 13 nonaffected first-degree relatives for five of these index cases had R110W mutation. Four heterozygous single nucleotide polymorphisms were found in the 5' region. One of the 11 patients with R110W also had T370M change in compound heterozygous form. Mutant R110W and T370M GCM2 proteins showed decreased binding with GCM recognition elements on EMSA indicating loss of function. Both wild-type and R110W mutant GCM2 proteins showed nuclear localization.


CONCLUSIONS
The present study indicates a significant association of R110W variant with IH. Absence of effect of heterozygous R110W mutation on DNA binding and presence of the same mutation in asymptomatic family members indicate that additional genetic (akin to T370M change) or nongenetic factors might contribute to the expression of diseases in IH. Alternatively, it is possible that association of R110W with IH could be due to linkage disequilibrium with the unidentified relevant genes in IH.
Tomar
Neeraj
N
Department of Endocrinology and Metabolism, All India Institute of Medical Sciences, New Delhi 110029, India.
Bora
Hema
H
Singh
Ratnakar
R
Gupta
Nandita
N
Kaur
Punit
P
Chauhan
Shyam Singh
SS
Sharma
Yagya Dutta
YD
Goswami
Ravinder
R
D016022:Case-Control Studies; D004252:DNA Mutational Analysis; D005192:Family Health; D005260:Female; D020022:Genetic Predisposition to Disease / Q000453:epidemiology; D006367:HeLa Cells; D006579:Heterozygote; D006801:Humans; D007011:Hypoparathyroidism / Q000453:epidemiology* / Q000235:genetics*; D008297:Male; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics*; D010375:Pedigree; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D020641:Polymorphism, Single Nucleotide; D015995:Prevalence; D017434:Protein Structure, Tertiary; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics*
C119532:GCM2 protein, human; D009687:Nuclear Proteins; D014157:Transcription Factors