Clayton-Smith J, Read A P, Donnai D
Department of Medical Genetics, St Mary's Hospital, Manchester, England.
Am J Med Genet. 1992 Feb 15;42(4):633-7. doi: 10.1002/ajmg.1320420440.
Monozygotic (MZ) twinning occurs with relatively high frequency in Wiedemann-Beckwith syndrome (WBS). Ten sets of MZ twins with WBS have been reported. Nine of these have been female and in each case the twins were discordant for the WBS phenotype. The tenth set was male. They were concordant for WBS and both had a duplication of chromosome 15 which they shared in common with their phenotypically normal mother. The WBS gene has been assigned to the locus 11p15 and there appear to be several different genetic mechanisms involving this locus which all give rise to WBS. An imprinting effect for the WBS gene has been proposed because of the transmission of the gene preferentially through the maternal line in some large pedigrees. We describe two further sets of female MZ twins with WBS. One pair is concordant and one discordant for the condition. The possible genetic mechanisms involved in the expression of WBS are discussed, with particular reference to twinning, genomic imprinting and X-inactivation which is thought to be associated with the occurrence of MZ twinning in females.
单卵双生（MZ）在威德曼-贝克威思综合征（WBS）中出现的频率相对较高。已报道了10对患有WBS的MZ双胞胎。其中9对为女性，且每对双胞胎的WBS表型不一致。第10对为男性。他们的WBS表型一致，并且都有15号染色体的重复，这与他们表型正常的母亲相同。WBS基因已被定位到11p15位点，似乎有几种涉及该位点的不同遗传机制，这些机制都会导致WBS。由于在一些大家族中该基因优先通过母系传递，因此有人提出WBS基因存在印记效应。我们描述了另外两对患有WBS的女性MZ双胞胎。一对双胞胎的病情一致，另一对不一致。本文讨论了WBS表达中可能涉及的遗传机制，特别提到了双生子现象、基因组印记和X染色体失活，后者被认为与女性MZ双生子的发生有关。
