Distinct Methylation Changes at the IGF2-H19 Locus in Congenital Growth Disorders and Cancer

Abstract

BackgroundDifferentially methylated regions (DMRs) are associated with many imprinted genes. In mice methylation at a DMR upstream of the H19 gene known as the Imprint Control region (IC1) is acquired in the male germline and influences the methylation status of DMRs 100 kb away in the adjacent Insulin-like growth factor 2 (Igf2) gene through long-range interactions. In humans, germline-derived or post-zygotically acquired imprinting defects at IC1 are associated with aberrant activation or repression of IGF2, resulting in the congenital growth disorders Beckwith-Wiedemann (BWS) and Silver-Russell (SRS) syndromes, respectively. In Wilms tumour and colorectal cancer, biallelic expression of IGF2 has been observed in association with loss of methylation at a DMR in IGF2. This DMR, known as DMR0, has been shown to be methylated on the silent maternal IGF2 allele presumably with a role in repression. The effect of IGF2 DMR0 methylation changes in the aetiology of BWS or SRS is unknown.Methodology/Principal FindingsWe analysed the methylation status of the DMR0 in BWS, SRS and Wilms tumour patients by conventional bisulphite sequencing and pyrosequencing. We show here that, contrary to previous reports, the IGF2 DMR0 is actually methylated on the active paternal allele in peripheral blood and kidney. This is similar to the IC1 methylation status and is inconsistent with the proposed silencing function of the maternal IGF2 allele. Beckwith-Wiedemann and Silver-Russell patients with IC1 methylation defects have similar methylation defects at the IGF2 DMR0, consistent with IC1 regulating methylation at IGF2 in cis. In Wilms tumour, however, methylation profiles of IC1 and IGF2 DMR0 are indicative of methylation changes occurring on both parental alleles rather than in cis.Conclusions/SignificanceThese results support a model in which DMR0 and IC1 have opposite susceptibilities to global hyper and hypomethylation during tumorigenesis independent of the parent of origin imprint. In contrast, during embryogenesis DMR0 is methylated or demethylated according to the germline methylation imprint at the IC1, indicating different mechanisms of imprinting loss in neoplastic and non-neoplastic cells.

Specific epigenetic alterations of IGF2-H19 locus in spermatozoa from infertile men

“…Our data provides evidence of a methylation of IGF2 DMR0 in spermatozoa. This is in concordance with the recent report of Murrell et al, 20 analysing the DMR0 methylation status in growth disorders, cancers and normal tissues and suggesting that the active paternal IGF2 allele is methylated at the DMR0 in cis with H19 methylation in normal individuals. In our study, the methylation pattern of DMR0 was similar in normal and abnormal sperms.…”

Hypermethylation of the IGF2 differentially methylated region 2 is a specific event in insulinomas leading to loss-of-imprinting and overexpression

“…Gastrinomas, non-functioning PETs, and SIETs displayed a methylation profile, which is comparable with the one observed in many types of sporadic tumors with a stable methylation of the H19 DMR, but significant hypomethylation of at least the IGF2 DMR0 (Murrell et al 2008). The hypomethylation of the DMR0 itself has been proposed as a DNA methylationbased biomarker for risk assessment of cancer development (Cui et al 2003, Kaneda & Feinberg 2005.…”

“…A second difference is found for the DMR0. This region is only differentially methylated in the mouse placenta, where methylation occurs on the maternal allele, while this region is methylated specifically on the paternal allele in human tissues (Murrell et al 2008). Taking these differences into account, the conserved hypermethylation of the murine and human DMR2 indicates that the upregulation of IGF2 expression might be a major factor in the tumorigenesis of insulinomas.…”

Association of genomic instability, and the methylation status of imprinted genes and mismatch-repair genes, with neural tube defects

“…They conclude that mechanisms of imprinting loss in neoplastic and non-neoplastic cells may be different. 37 Wang et al 38 researched the relation between hypo-methylation of long interspersed nucleotide elements (LINE-1) and risk of neural tube defects, and found that methylation the levels of genomic DNA and LINE-1 decreased significantly in the neural tissue of NTD samples. Hypo-methylation of LINE-1 is thought to be connected to genomic instability and endogenous DNA double-strand breaks in some cancers.…”