2314077a-5608-42eb-9936-f5790f20b951
title
An association between variants in the  IGF2  gene and Beckwith-Wiedemann syndrome: interaction between genotype and epigenotype.
80eb6127-afaa-4361-acc6-d2d308d21d6e
abstract
Beckwith-Wiedemann syndrome (BWS) is a fetal overgrowth disorder involving the deregulation of a number of genes, including  IGF2  and  CDKN1C , in the imprinted gene cluster on chromosome 11p15.5. In sporadic BWS cases the majority of patients have epimutations in this region. Loss of imprinting of the  IGF2  gene is frequently observed in BWS, as is reduced  CDKN1C  expression related to loss of maternal allele-specific methylation (LOM) of the differentially methylated region  KvDMR1 . The causes of epimutations are unknown, although recently an association with assisted reproductive technologies has been described. To date the only genetic mutations described in BWS are in the  CDKN1C  gene. In order to screen for other genetic predispositions to BWS, the conserved sequences between human and mouse differentially methylated regions (DMRs) of the  IGF2  gene were analyzed for variants. Four single nucleotide polymorphisms (SNPs) were found in DMR0 ( T123C ,  G358A ,  T382G  and  A402G ) which occurred in three out of 16 possible haplotypes: TGTA, CATG and CAGA. DNA samples from a cohort of sporadic BWS patients and healthy controls were genotyped for the DMR0 SNPs. There was a significant increase in the frequency of the CAGA haplotype and a significant decrease in the frequency of the CATG haplotype in the patient cohort compared to controls. These associations were still significant in a BWS subgroup with  KvDMR1  LOM, suggesting that the G allele at  T382G  SNP (CAGA haplotype) is associated with LOM at  KvDMR1 . This indicates either a genetic predisposition to LOM or interactions between genotype and epigenotype that impinge on the disease phenotype.