Genetic and epigenetic states of the GNAS complex in pseudohypoparathyroidism type Ib using methylation-specific multiplex ligation-dependent probe amplification assay

• Published in: European journal of endocrinology Vol. 168; no. 2; pp. 169 - 175
• Main Authors: Yuno, Akiko, Usui, Takeshi, Yambe, Yuko, Higashi, Kiichiro, Ugi, Satoshi, Shinoda, Junji, Mashio, Yasuo, Shimatsu, Akira
• Format: Journal Article
• Language: English
• Published: Bristol BioScientifica 01.02.2013
• Subjects: Biological and medical sciences; Chromogranins; Clinical Study; DNA Methylation; Endocrinopathies; Epigenesis, Genetic; Female; Fundamental and applied biological sciences. Psychology; Genomic Imprinting; GTP-Binding Protein alpha Subunits, Gs - genetics; Humans; Male; Medical sciences; Multiplex Polymerase Chain Reaction; Non tumoral diseases. Target tissue resistance. Benign neoplasms; Parathyroids. Parafollicular cells. Cholecalciferol. Phosphocalcic homeostasis (diseases); Pseudohypoparathyroidism - genetics; Retrospective Studies; Sequence Deletion; Vertebrates: endocrinology; Endocrinopathy; Amplification; Assay; Ligature; Pseudohypoparathyroidism; Genetics; Methylation; Probe; Endocrinology; Genetic disease; Complexity
• ISSN: 0804-4643; 1479-683X; 1479-683X
• DOI: 10.1530/EJE-12-0548

ContextPseudohypoparathyroidism type Ib (PHP-Ib) is a rare disorder resulting from genetic and epigenetic aberrations in the GNAS complex. PHP-Ib, usually defined by renal resistance to parathyroid hormone, is due to a maternal loss of GNAS exon A/B methylation and leads to decreased expression of the stimulatory G protein α (Gsα) in specific tissues.ObjectiveTo clarify the usefulness of methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA), we evaluated genetic and epigenetic changes of the GNAS locus in Japanese PHP-Ib patients.DesignRetrospective case series.PatientsWe studied 13 subjects with PHP-Ib (three families with eight affected members and one unaffected member and four sporadic cases).MeasurementsThe methylation status of GNAS differentially methylated regions (DMRs) was evaluated using MS-MLPA. The main outcome measure was the presence of deletion mutations in the GNAS locus and STX16, which were assessed using MLPA.ResultsIn all familial PHP-Ib cases, a ∼3 kb deletion of STX16 and demethylation of the A/B domain were identified. In contrast, no deletion was detected throughout the entire GNAS locus region in the sporadic cases. Broad methylation abnormalities were observed in the GNAS DMRs.ConclusionsMS-MLPA allows for precise and rapid analysis of the methylation status in GNAS DMRs as well as the detection of microdeletion mutations in PHP-Ib. Results confirm the previous findings in this disorder and demonstrate that this method is valuable for the genetic evaluation and visualizing the methylation status. The MS-MLPA assay is a useful tool that may facilitate making the molecular diagnosis of PHP-Ib.