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Epigenetics. 2013 Oct;8(10):1053-60. doi: 10.4161/epi.25812. Epub 2013 Aug 5.

Quantitative DNA methylation analysis improves epigenotype-phenotype correlations in Beckwith-Wiedemann syndrome.

Author information

1
Division of Pathology; Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico; Milano, Italy.
2
Division of Pathology; Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico; Milano, Italy; Department of Pathophysiology and Transplantation; Università degli Studi di Milano; Milano, Italy.
3
Department of Health Sciences; Università degli Studi di Milano; Milano, Italy.
4
Clinical Genetics; Pediatric Department; S. Gerardo Hospital; Fondazione MBBM; Università di Milano-Bicocca; Monza, Italy.
5
Department of Pathophysiology and Transplantation; Università degli Studi di Milano; Milano, Italy.
6
Clinical Genetics Unit; Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico; Milano, Italy.
7
Pediatric Oncology Unit; Fondazione IRCCS Istituto Nazionale dei Tumori; Milano, Italy.
8
Molecular Biology Laboratory; Istituto Auxologico Italiano; Milano, Italy.
9
Molecular Bases of Genetic Risk and Genetic Testing Unit; Department of Preventive and Predictive Medicine; Fondazione IRCCS Istituto Nazionale dei Tumori; Milano, Italy.
10
Department of Health Sciences; Università degli Studi di Milano; Milano, Italy; Molecular Biology Laboratory; Istituto Auxologico Italiano; Milano, Italy.
11
Division of Pathology; Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico; Milano, Italy; Department of Health Sciences; Università degli Studi di Milano; Milano, Italy.

Abstract

Beckwith-Wiedemann syndrome (BWS) is a rare disorder characterized by overgrowth and predisposition to embryonal tumors. BWS is caused by various epigenetic and/or genetic alterations that dysregulate the imprinted genes on chromosome region 11p15.5. Molecular analysis is required to reinforce the clinical diagnosis of BWS and to identify BWS patients with cancer susceptibility. This is particularly crucial prenatally because most signs of BWS cannot be recognized in utero. We established a reliable molecular assay by pyrosequencing to quantitatively evaluate the methylation profiles of ICR1 and ICR2. We explored epigenotype-phenotype correlations in 19 patients that fulfilled the clinical diagnostic criteria for BWS, 22 patients with suspected BWS, and three fetuses with omphalocele. Abnormal methylation was observed in one prenatal case and 19 postnatal cases, including seven suspected BWS. Seven cases showed ICR1 hypermethylation, five cases showed ICR2 hypomethylation, and eight cases showed abnormal methylation of ICR1 and ICR2 indicating paternal uniparental disomy (UPD). More cases of ICR1 alterations and UPD were found than expected. This is likely due to the sensitivity of this approach, which can detect slight deviations in methylation from normal levels. There was a significant correlation (p<0.001) between the percentage of ICR1 methylation and BWS features: severe hypermethylation (range: 75-86%) was associated with macroglossia, macrosomia, and visceromegaly, whereas mild hypermethylation (range: 55-59%) was associated with umbilical hernia and diastasis recti. Evaluation of ICR1 and ICR2 methylation by pyrosequencing in BWS can improve epigenotype-phenotype correlations, detection of methylation alterations in suspected cases, and identification of UPD.

KEYWORDS:

BWS; DNA methylation; UPD; genomic imprinting; pyrosequencing

PMID:
23917791
PMCID:
PMC3891686
DOI:
10.4161/epi.25812
[Indexed for MEDLINE]
Free PMC Article

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