Analysis of the IGF2/H19 imprinting control region uncovers new genetic defects, including mutations of OCT-binding sequences, in patients with 11p15 fetal growth disorders.
The imprinted expression of the IGF2 and H19 genes is controlled by the imprinting control region 1 (ICR1) located at chromosome 11p15.5. This methylation-sensitive chromatin insulator works by binding the zinc-finger protein CTCF in a parent-specific manner. DNA methylation defects involving the ICR1 H19/IGF2 domain result in two growth disorders with opposite phenotypes: an overgrowth disorder, the Beckwith-Wiedemann syndrome (maternal ICR1 gain of methylation in 10% of BWS cases) and a growth retardation disorder, the Silver-Russell syndrome (paternal ICR1 loss of methylation in 60% of SRS cases). Although a few deletions removing part of ICR1 have been described in some familial BWS cases, little information is available regarding the mechanism of ICR1 DNA methylation defects. We investigated the CTCF gene and the ICR1 domain in 21 BWS patients with ICR1 gain of methylation and 16 SRS patients with ICR1 loss of methylation. We identified four constitutional ICR1 genetic defects in BWS patients, including a familial case. Three of those defects are newly identified imprinting defects consisting of small deletions and a single mutation, which do not involve one of the CTCF binding sites. Moreover, two of those defects affect OCT-binding sequences which are suggested to maintain the unmethylated state of the maternal allele. A single-nucleotide variation was identified in a SRS patient. Our data extends the spectrum of constitutive genetic ICR1 abnormalities and suggests that extensive and accurate analysis of ICR1 is required for appropriate genetic counseling in BWS patients with ICR1 gain of methylation.
Demars
Julie
J
Epigenetics in Human Health and Disease, Baker IDI Heart and Diabetes Institute, Melbourne, 3004 VIC, Australia.
Shmela
Mansur Ennuri
ME
Rossignol
Sylvie
S
Okabe
Jun
J
Netchine
Irène
I
Azzi
Salah
S
Cabrol
Sylvie
S
Le Caignec
Cédric
C
David
Albert
A
Le Bouc
Yves
Y
El-Osta
Assam
A
Gicquel
Christine
C
D001483:Base Sequence; D001506:Beckwith-Wiedemann Syndrome / Q000235:genetics; D002880:Chromosomes, Human, Pair 11 / Q000235:genetics*; D015331:Cohort Studies; D019175:DNA Methylation; D005260:Female; D005317:Fetal Growth Retardation / Q000235:genetics* / Q000378:metabolism; D018392:Genomic Imprinting; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000235:genetics* / Q000378:metabolism; D008297:Male; D009154:Mutation; D050810:Octamer Transcription Factors / Q000378:metabolism*; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics* / Q000378:metabolism
C094335:H19 long non-coding RNA; D050810:Octamer Transcription Factors; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D007335:Insulin-Like Growth Factor II