1. High frequency of paternal iso or heterodisomy at chromosome 20 associated with sporadic pseudohypoparathyroidism 1B
- Author
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Marie-Laure Kottler, Matthieu Decamp, Nadia Coudray, Céline Ballandonne, Claire Bracquemart, Cindy Colson, Nicolas Gruchy, Hervé Mittre, Arnaud Molin, Harald Jüppner, Rieko Takatani, Nicolas Richard, Service de Génétique [CHU Caen], CHU Caen, Normandie Université (NU)-Tumorothèque de Caen Basse-Normandie (TCBN)-Normandie Université (NU)-Tumorothèque de Caen Basse-Normandie (TCBN)-Université de Caen Normandie (UNICAEN), Normandie Université (NU), Biologie, génétique et thérapies ostéoarticulaires et respiratoires (BIOTARGEN), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU), Œstrogènes, reproduction, cancer (OeReCa), Chiba University Hospital, Endocrine Unit, and Massachusetts General Hospital [Boston]
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Adult ,Male ,0301 basic medicine ,congenital, hereditary, and neonatal diseases and abnormalities ,Histology ,Physiology ,Endocrinology, Diabetes and Metabolism ,Chromosomes, Human, Pair 20 ,030209 endocrinology & metabolism ,Biology ,Article ,Cohort Studies ,03 medical and health sciences ,0302 clinical medicine ,Gene Frequency ,GNAS complex locus ,medicine ,Humans ,Epigenetics ,Allele ,Imprinting (psychology) ,Pseudohypoparathyroidism ,Genetics ,Methylation ,Uniparental Disomy ,medicine.disease ,030104 developmental biology ,Differentially methylated regions ,[SDV.GEN.GH]Life Sciences [q-bio]/Genetics/Human genetics ,biology.protein ,Female ,Chromosome 20 - Abstract
International audience; Pseudohypoparathyroidism 1B (PHP1B) is caused by maternal epigenetic defects in the imprinted GNAS cluster. PHP1B can follow an autosomal dominant mode of inheritance or occur sporadically (spor-PHP1B). These latter patients present broad methylation changes of two or more differentially methylated regions (DMR) that, when mimicking the paternal allele, raises the suspicious of the occurrence of paternal uniparental disomy of chromosome 20 (upd(20)pat). A cohort of 33 spor-PHP1B patients was screened for upd(20)pat using comparative genomic hybridization with SNP-chip. Methylation analyses were assessed by methylation specific-multiplex ligation-dependent probe amplification. Upd(20)pat was identified in 6 patients, all exhibiting typical paternal methylation pattern compared to normal controls, namely a complete loss of methylation of GNAS A/B:TSS-DMR, negligible methylation at GNAS-AS1 :TSS-DMR and GNAS-XL:Ex1-DMR and complete gain of methylation at GNAS-NESP:TSS-DMR. The overall frequency of upd(20) is 18% in our cohort when searched considering both severe and partial loss of imprinting. However, twenty five patients displayed severe methylation pattern and the upd(20)pat frequency reaches 24% when searching in this group. Consequently, up to day, upd(20)pat is the most common anomaly than other genetic alterations in spor-PHP1B patients. Upd(20)pat occurrence is not linked to the parental age in contrast to upd(20)mat, strongly associated with an advanced maternal childbearing age. This study provides criteria to guide further investigations for upd(20)pat needed for an adequate genetic counseling.
- Published
- 2019
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