Analysis of the GNAS1 Gene in Albright’s Hereditary Osteodystrophy

Abstract

Albright's hereditary osteodystrophy (AHO) is characterized by phenotypic signs that typically include brachydactyly and sc calcifications occurring with or without hormone resistance toward PTH or other hormones such as thyroid hormone or gonadotropins. Different inactivating mutations of the gene GNAS1 encoding Gsalpha lead to a reduced Gsalpha protein activity in patients with AHO and pseudohypoparathyroidism type Ia or without resistance to PTH (pseudopseudohypoparathyroidism). We investigated 29 unrelated patients with AHO and pseudohypoparathyroidism type Ia or pseudopseudohypoparathyroidism and their affected family members performing functional and molecular genetic analysis of Gsalpha. In vitro determination of Gsalpha protein activity in erythrocyte membranes was followed by the investigation of the whole coding region of the GNAS1 gene using PCR, nonisotopic single strand conformation analysis, and direct sequencing of the PCR products. All patients showed a reduced Gsalpha protein activity (mean 59% compared with healthy controls). In 21/29 (72%) patients, 15 different mutations in GNAS1 including 11 novel mutations were detected. In addition we add five unrelated patients with a previously described 4 bp deletion in exon 7 (Delta GACT, codon 189/190), confirming the presence of a hot spot for loss of function mutations in GNAS1. In eight patients, no molecular abnormality was found in the GNAS1 gene despite a functional defect of Gsalpha. We conclude that biochemical and molecular analysis of Gsalpha and its gene GNAS1 can be valuable tools to confirm the diagnosis of AHO. However, in some patients with reduced activity of Gsalpha, the molecular defect cannot be detected in the exons encoding the common form of Gsalpha.

Molecular Analysis of the GNAS1 Gene for the Correct Diagnosis of Albright Hereditary Osteodystrophy and Pseudohypoparathyroidism

“…A causal mutation in GNAS1 was found in 15 of these families, i.e. a mutation detection rate of 71.4%, as reported for other series (14,39).…”

Early manifestation of calcinosis cutis in pseudohypoparathyroidism type Ia associated with a novel mutation in the GNAS gene

“…From our personal experience we presume that there is a wide individual variation of occurrence. Congenital hypothyroidism is another notable feature in our patient, as most individuals with AHO and PHP Ia show signs of hypothyroidism only in later life (8,11,15). A typical finding in patients suffering from the combination of AHO and congenital hypothyroidism is disturbed psychomotor development in spite of sufficient thyroid hormone-substitution therapy (16).…”

“…Exons 2-13 of the GNAS gene including intron/exon boundaries were individually amplified in 10 fragments by PCR using the oligonucleotide primers reported previously (8). 100 ng DNA in a final volume of 50 ml using 20 pmol of each primer, 200 mmol or 2 mmol dNTP, 0.5 or 1 U Taq polymerase (AmpliTaq; Perkin-Elmer Corp., Norwalk, CT, USA), 20 mmol Tris (pH 8.4), 1.0 -2.5 mmol MgCl 2 were applied to an initial denaturation at 94 8C for 5 min, followed by 34 cycles of annealing at 52 -62 8C for 90 s, elongation at 72 8C for 2 min, and denaturation at 94 8C for 75 s, and a final elongation at 72 8C for 5 min.…”

Diagnosis and management of pseudohypoparathyroidism and related disorders: first international consensus statement

“…Unassisted and uneventful pregnancies have been reported in female patients with PHP1A 120,221 and autosomal dominant PHP1B 44,72,153,160,216 ; these pregnancies are more often seen in women with PPHP, who give birth to offspring with PHP1A 24,36,45,117,122,[221][222][223] . In a few cases, either infertility 193 or the need for the use of an assisted reproductive technique to obtain pregnancy 47,224,225 have been reported.…”