Analysis of the methylation status of the KCNQ1OT and H19 genes in leukocyte DNA for the diagnosis and prognosis of Beckwith–Wiedemann syndrome

Abstract

Beckwith ± Wiedemann syndrome (BWS) is an overgrowth disorder involving developmental abnormalities, tissue and organ hyperplasia and an increased risk of embryonal tumours (most commonly Wilms tumour). This multigenic disorder is caused by dysregulation of the expression of imprinted genes in the 11p15 chromosomal region. Molecular diagnosis of BWS is currently difficult, mostly due to the large spectrum of genetic and epigenetic abnormalities. The other difficulty in managing BWS is the identification of patients at risk of tumour. An imprinted antisense transcript within KCNQ1, called KCNQ1OT (also known as LIT1), was recently shown to be normally expressed from the paternal allele. A loss of imprinting of the KCNQ1OT gene, associated with the loss of maternal allele-specific methylation of the differentially methylated region KvDMR1 has been described in BWS patients. The principal aim of this study was to evaluate the usefulness of KvDMR1 methylation analysis of leukocyte DNA for the diagnosis of BWS. The allelic status of the 11p15 region and the methylation status of the KCNQ1OT and H19 genes were investigated in leukocyte DNA from 97 patients referred for BWS and classified into two groups according to clinical data: complete BWS (CBWS) (n=61) and incomplete BWS (IBWS) (n=36). Fifty-eight (60%) patients (39/61 CBWS and 19/36 IBWS) displayed abnormal demethylation of KvDMR1. In 11 of the 56 informative cases, demethylation of KvDMR1 was related to 11p15 uniparental disomy (UPD) (nine CBWS and two IBWS). Thirteen of the 39 patients with normal methylation of KvDMR1 displayed hypermethylation of the H19 gene. These 13 patients included two siblings with 11p15 trisomy. These results show that analysis of the methylation status of KvDMR1 and the H19 gene in leukocyte DNA is useful in the diagnosis of 11p15-related overgrowth syndromes, resulting in the diagnosis of BWS in more than 70% of investigated patients. We also evaluated clinical and molecular features as prognostic factors for tumour and showed that mosaicism for 11p15 UPD and hypermethylation of the H19 gene in blood cells were associated with an increased risk of tumour.

The Frequency of Methylation Abnormalities Among Estonian Patients Selected by Clinical Diagnostic Scoring Systems for Silver–Russell Syndrome and Beckwith–Wiedemann Syndrome

“…Compared to other studies (Gaston et al, 2001;Bliek et al, 2009;Calvello et al, 2013;Mussa et al, 2013;Ibrahim et al, 2014), our detection rate of epigenetic alterations in chromosome 11p15 was significantly lower in the BWS group, but comparable in the SRS group (Bartholdi et al, 2009;Peña-herrera et al, 2010). In our group, 5 of 13 (38%) SRS patients with positive clinical scoring had abnormal methylation in chromosome 11p15.…”

“…In our group, 5 of 13 (38%) SRS patients with positive clinical scoring had abnormal methylation in chromosome 11p15. In the BWS group, of all the patients who met the clinical criteria, only one patient was diagnosed with ICR2 hypomethylation (8%), whereas in other studies, the detection rate for imprinting disorders in 11p15 has been 28-72% (Gaston et al, 2001;Calvello et al, 2013;Mussa et al, 2013;Baskin et al, 2014;Eggermann et al, 2014). When we compared the symptoms of our BWS group patients with recent criteria by Ibrahim et al (2014), eight patients met the minimum score for BWS, but nevertheless the detection rate remained low (12.5%).…”

Lessons from BWS twins: complex maternal and paternal hypomethylation and a common source of haematopoietic stem cells

“…27 In the majority of BWS cases, molecular diagnosis relies on analysis of leukocyte-derived DNA. In two large studies, 24,28 DMR2 hypomethylation was found in DNA derived from blood samples of both the affected and nonaffected twins of discordant twin pairs. It has been proposed that aberrant methylation in the blood of the healthy twin is caused by vascular connections in the placenta that is shared by both MZ (monochorionic, diamnionic) twins.…”

Methylation Status of H19/IGF2 Differentially Methylated Region in in vitro Human Blastocysts Donated by Healthy Couples

“…Hypomethylation of ICR1 is observed in RSS patients [13,14] , while hypermethylation of ICR1, which is associated with increased IGF2 expression, is observed in BWS patients [15] . It has been shown that paternally expressed genes (such as IGF2) tend to increase fetal growth, whereas those expressed maternally , such as H19, restrict fetal growth [16][17][18] .…”