title: Discordant KCNQ1OT1 imprinting in sets of monozygotic twins discordant for Beckwith-Wiedemann syndrome.
abstract: Beckwith-Wiedemann syndrome (BWS) presents with visceromegaly, macroglossia, tumor predisposition and other congenital abnormalities, and is usually associated with abnormalities of chromosome 11p15. A number of identical twin pairs, mostly female, have been reported to be discordant for BWS. We show here that the incidence of female monozygotic twins among patients with BWS is dramatically increased over that of the general population. A cluster of imprinted genes within 11p15 is thought to be coordinately regulated via the imprinted expression of KCNQ1OT1, which encodes an untranslated RNA. In skin fibroblasts from five monozygotic twin pairs discordant for BWS, each affected twin had an imprinting defect at KCNQ1OT1 on 11p15, whereas the unaffected twin did not. Five additional monozygotic twin pairs, for whom only blood was available, also displayed an imprinting defect at KCNQ1OT1. It is possible that discordance for BWS in MZ twins is due to unequal splitting of the inner cell mass during twinning, thereby causing differential maintenance of imprinting at KCNQ1OT1. Alternatively, we propose that KCNQ1OT1 is especially vulnerable to a loss of imprinting event, caused by a lack of maintenance DNA methylation at a critical stage of preimplantation development, and that this loss of imprinting predisposes to twinning as well as to discordance for BWS. These data underscore the importance of continued surveillance of children born following assisted reproductive technologies that impact the preimplantation embryo.
authors.affiliation: Division of Clinical and Metabolic Genetics and the Research Institute, Department of Paediatrics Hospital for Sick Children, Toronto, Ontario, Canada. rweks@sickkids.on.ca
authors.forename: Rosanna
authors.initials: R
authors.lastname: Weksberg
authors.forename: Cheryl
authors.initials: C
authors.lastname: Shuman
authors.forename: Oana
authors.initials: O
authors.lastname: Caluseriu
authors.forename: Adam C
authors.initials: AC
authors.lastname: Smith
authors.forename: Yan-Ling
authors.initials: YL
authors.lastname: Fei
authors.forename: Joy
authors.initials: J
authors.lastname: Nishikawa
authors.forename: Tracy L
authors.initials: TL
authors.lastname: Stockley
authors.forename: Lyle
authors.initials: L
authors.lastname: Best
authors.forename: David
authors.initials: D
authors.lastname: Chitayat
authors.forename: Ann
authors.initials: A
authors.lastname: Olney
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Ives
authors.forename: Adele
authors.initials: A
authors.lastname: Schneider
authors.forename: Timothy H
authors.initials: TH
authors.lastname: Bestor
authors.forename: Madeline
authors.initials: M
authors.lastname: Li
authors.forename: Paul
authors.initials: P
authors.lastname: Sadowski
authors.forename: Jeremy
authors.initials: J
authors.lastname: Squire
mesh_terms: D001506:Beckwith-Wiedemann Syndrome / Q000235:genetics*; D019175:DNA Methylation; D004200:Diseases in Twins / Q000235:genetics*; D004303:Dosage Compensation, Genetic; D005347:Fibroblasts / Q000502:physiology; D018392:Genomic Imprinting; D006801:Humans; D022661:RNA, Untranslated; D012744:Sex Ratio; D014430:Twins, Monozygotic / Q000235:genetics*
chemical_list: D022661:RNA, Untranslated