Presence and significance of a R110W mutation in the DNA-binding domain of GCM2 gene in patients with isolated hypoparathyroidism and their family members

Abstract

Objective: Glial cells missing 2 (GCM2) gene encodes a parathyroid-specific transcription factor. We assessed GCM2 gene sequence in patients with isolated hypoparathyroidism (IH). Design: Case-control study. Methods: Complete DNA sequencing of the GCM2 gene including its exons, promoter, and 5 0 and 3 0UTRs 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 K7 ). 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 0 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.

Calcium-Sensing Receptor Autoantibodies and Idiopathic Hypoparathyroidism

“…The low prevalence of the CaSRAbs in hypoparathyroidism could be due to the lack of a sensitive CaSRAb assay for epitopes not measured in the present study. Alternatively, it could reflect heterogeneity in the etiology of idiopathic hypoparathyroidism as indicated by GCM2 mutations, NALP5Ab (7,14), and an occasional PTH gene mutation in these patients. …”

“…Cases included 147 patients with idiopathic hypoparathyroidism attending the endocrine clinics of our tertiary care center during 1998 -2011 (5,7,10,14). Three of these had APECED syndrome (14).…”

“…In the present study, sequencing was performed for all patients in whom sufficient genomic DNA was available for the PTH (n ϭ 139) and CaSR gene (n ϭ 135) mutations. In addition, 37 patients were also assessed for the R110W mutation in the GCM2 gene in addition to the 101 reported earlier (7).…”

“…Genetic abnormalities associated with idiopathic hypoparathyroidism include mutations of the parathyroid hormone (PTH) and calcium-sensing receptor (CaSR) (4 -6) genes. Recently the R110W mutation of the GCM2 (glial cell missing 2) gene was observed in 10.9% of these patients (7).…”

Genetic Disorders Caused by Mutations in the PTH/PTHrP Receptor and Downstream Effector Molecules

“…4 GCM2 mutations can be associated with autosomal recessive and dominant forms of isolated hypoparathyroidism. [62][63][64][65][66][67][68] Furthermore, mutations in GNA11, the gene encoding Gα11, one of the signaling proteins at the calcium-sensing receptor, were recently shown to cause an autosomal dominant form of hypoparathyroidism. 69,70 Lastly, FAM111A mutations have been identified in patients with hypoparathyroidism associated with impaired skeletal development in the context of KennyCaffey syndrome type 2.…”