title: Genetic and epigenetic states of the GNAS complex in pseudohypoparathyroidism type Ib using methylation-specific multiplex ligation-dependent probe amplification assay.
abstract: BACKGROUND
  Pseudohypoparathyroidism 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.
  
  
  OBJECTIVE
  To 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.
  
  
  METHODS
  Retrospective case series.
  
  
  METHODS
  We studied 13 subjects with PHP-Ib (three families with eight affected members and one unaffected member and four sporadic cases).
  
  
  METHODS
  The 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.
  
  
  RESULTS
  In 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.
  
  
  CONCLUSIONS
  MS-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.
authors.affiliation: Clinical Research Institute, National Hospital Organization Kyoto Medical Center, 1-1 Mukaihata-cho, Fukakusa, Fushimi-ku, Kyoto 612-8555, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Yuno
authors.forename: Takeshi
authors.initials: T
authors.lastname: Usui
authors.forename: Yuko
authors.initials: Y
authors.lastname: Yambe
authors.forename: Kiichiro
authors.initials: K
authors.lastname: Higashi
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ugi
authors.forename: Junji
authors.initials: J
authors.lastname: Shinoda
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Mashio
authors.forename: Akira
authors.initials: A
authors.lastname: Shimatsu
mesh_terms: D002864:Chromogranins; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005260:Female; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000235:genetics*; D018392:Genomic Imprinting; D006801:Humans; D008297:Male; D060885:Multiplex Polymerase Chain Reaction; D011547:Pseudohypoparathyroidism / Q000235:genetics*; D012189:Retrospective Studies; D017384:Sequence Deletion
chemical_list: D002864:Chromogranins; C406732:GNAS protein, human; D019205:GTP-Binding Protein alpha Subunits, Gs