In situ hybridization shows direct evidence of skewed X inactivation in one of monozygotic twin females manifesting Duchenne muscular dystrophy
✍ Scribed by Zneimer, Susan M. ;Schneider, Nancy R. ;Richards, C. Sue
- Book ID
- 102703041
- Publisher
- John Wiley and Sons
- Year
- 1993
- Tongue
- English
- Weight
- 748 KB
- Volume
- 45
- Category
- Article
- ISSN
- 0148-7299
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✦ Synopsis
A novel combination of conventional and molecular cytogenetic techniques was used to investigate the expression of an X-linked recessive disorder in one of monozygotic (MZ) twin females. These twins carry a deletion, approximately 300 kb in length, in one of their X chromosomes within the dystrophin gene, which is responsible for Duchenne muscular dystrophy (DMD) in one twin [Richards et al.: Am J Hum Genet 46:672-681,19901. A unique DNA fragment generated from a n exon within this gene deletion was hybridized in situ to both twins' metaphase chromosomes, a probe which would presumably hybridize only to the normal X chromosome and not to the X chromosome carrying the gene deletion. Chromosomes were identified by reverse-banding (R-banding) a n d by the addition of 5-bromodeoxyuridine (BrdU) in culture to distinguish early and late replicating X chromosomes, corresponding to active a n d inactive X chromosomes, respectively. Hybridization experiments showed predominant inactivation of the normal X chromosome in the twin with DMD. This is the fwst report showing direct evidence at the chromosome level of unequal inactivation of cytogenetically normal X chromosomes resulting in the manifestation of an X-linked recessive disorder in one of monozygotic twin females. This study may now facilitate other research of unequal X inactivation a n d of females manifesting X-linked recessive disorders.