Linked Life Data

12374764

Source:http://linkedlifedata.com/resource/pubmed/id/12374764

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
22
pubmed:dateCreated
2002-10-10
pubmed:databankReference
pubmed:abstractText
Pseudohypoparathyroidism Ib (PHPIb), characterized by parathyroid hormone-resistant hypocalcemia and hyperphosphatemia, is caused by a deregulation in the imprinting status of the GNAS1 cluster, comprising exons XL, NESP55 and 1A and the coding exons of Gsalpha. Differences in methylation of exon 1A and sporadically also of exons XL and NESP55 were found and thought to result in long-range effects on Gsalpha expression, limited to the proximal renal tubules. The exact imprinting defect is not precisely localized, and the expected differences in Gsalpha protein level and function are mainly hypothetical. We describe a PHPIb patient with lack of methylation of the exon XL and 1A promoters, and biallelic methylation of the NESP55 promoter. Platelets of this patient show a functional Gs defect, decreased cAMP formation upon Gs-receptor stimulation, normal Gsalpha sequence but reduced Gsalpha protein levels. Transcriptional deregulation between the now biallelically active promoters of both exon 1A and exon 1 of Gsalpha could explain the decreased Gsalpha expression in platelets and presumably in the proximal renal tubules. We found decreased NESP55 and increased XLalphas protein levels in platelets, in agreement with the methylation status of their corresponding first exons. In a megakaryocytic cell line MEG-01, exon 1A is methylated on both alleles, in contrast to the normally maternally methylated exon 1A in leukocytes. Experimental demethylation of exon 1A in MEG-01 cells led to reduced Gsalpha expression, in agreement with the observations in the patient. Platelet studies may therefore allow easy evaluation of disturbances of the GNAS1 cluster in PHPIb patients.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0964-6906
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
11
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
2741-50
pubmed:dateRevised
2009-11-19
pubmed:meshHeading
pubmed:year
2002
pubmed:articleTitle
Pseudohypoparathyroidism type Ib with disturbed imprinting in the GNAS1 cluster and Gsalpha deficiency in platelets.
pubmed:affiliation
Center for Molecular and Vascular Biology, Leuven, Belgium.
pubmed:publicationType
Journal Article, Case Reports, Research Support, Non-U.S. Gov't