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Identification and functional analysis of a novel CaSR mutation in a family with familial hypocalciuric hypercalcemia.

Authors :
Kim ES
Kim SY
Lee JY
Han JH
Sohn TS
Son HS
Moon SD
Source :
Journal of bone and mineral metabolism [J Bone Miner Metab] 2016 Nov; Vol. 34 (6), pp. 662-667. Date of Electronic Publication: 2015 Sep 19.
Publication Year :
2016

Abstract

The calcium-sensing receptor (CaSR) is a G-protein-coupled receptor that plays an essential role in maintaining calcium homeostasis. In the present study, we analyzed the CaSR gene in a Korean family with familial hypocalciuric hypercalcemia (FHH). Genetic studies were performed by direct sequence analysis of the CaSR gene in genomic DNA obtained from peripheral leukocytes. A novel heterozygous G to T substitution at nucleotide position 1711 in exon 6, resulting in the G571W mutation, was identified in the CaSR gene in a 26-year-old female with asymptomatic hypercalcemia, a low calcium/creatinine clearance ratio, and normal intact parathyroid hormone. To study CaSR expression, the mutation was introduced by site-directed mutagenesis into a wild-type (WT) CaSR-expressing pCR3.1 vector, and COS-7 cells were transfected with either the WT or mutant CaSR-containing vector. Transfected cells loaded with Fura-2/AM, a fluorescent indicator of Ca <superscript>2+</superscript> , were assessed for CaSR function by the change in intracellular calcium [as measured by the 340 nm/380 nm fluorescence intensity ratio (F340/F380)] made in response to challenge with extracellular Ca <superscript>2+</superscript> . Both WT and G571W cells had equivalent amounts of CaSR protein in the cell membrane. However, after challenge with extracellular Ca <superscript>2+</superscript> , cells transfected with G571W CaSR responded with a lower F340/F380 ratio than those transfected with WT CaSR and showed decreased sensitivity to extracellular Ca <superscript>2+</superscript> concentrations. The G571W mutation had therefore impaired the CaSR function. In conclusion, we identified a novel loss-of-function mutation, G571W, in the CaSR gene in a Korean family with FHH.

Details

Language :
English
ISSN :
1435-5604
Volume :
34
Issue :
6
Database :
MEDLINE
Journal :
Journal of bone and mineral metabolism
Publication Type :
Academic Journal
Accession number :
26386835
Full Text :
https://doi.org/10.1007/s00774-015-0713-z