Skewed inactivation of an X chromosome deleted at the dystrophin gene in an asymptomatic mother and her affected daughter |
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Authors: | Frédérique Tihy Nicolas Vogt Dominique Recan Bernard Malfoy France Leturcq Michelle Coquet Françoise Serville Daniel Fontan Jean-Michel Guillard Jean-Claude Kaplan Bernard Dutrillaux Nicole Lemieux |
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Institution: | (1) Département de Pathologie, Faculté de Médecine, Université de Montréal, Montréal, Canada;(2) Section de Biologie, URA 620 CNRS, Institut Curie, Paris, France;(3) Laboratoire de Biochimie Génétique, Hôpital Cochin, Paris, France;(4) Services Neuropathologie et Pédiatrie, Hôpital Pellegrin, Bordeaux, France;(5) Section de Biologie, CNRS URA 620, Institut Curie, 26, Rue d'Ulm, F-75231 Paris Cedex, 05, France |
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Abstract: | A girl with severe Becker muscular dystrophy and apparently normal chromosomes had a heterozygous deletion for exons 51, 52, and 53 of the dystrophin gene. This deletion was transmitted by her mother, who was unaffected. To differentiate the normal and the deleted X chromosomes, fluorescence in situ hybridization (FISH) was applied to metaphase chromosomes, using probes for both exons 51 and 52, which are only 388 and 113 base pairs long, respectively. FISH signals were observed in one or both chromatids of one chromosome, but never on both chromosomes, suggesting the lack of hybridization on the deleted X chromosome. Using 5-bromodeoxyuridine incorporation to differentiate the late (inactive) and the early replicating (active) X chromosomes, 77% of the signals were observed on the active X chromosomes in the mother. This percentage was only 18% in the daughter, suggesting that skewed inactivation of the X chromosomes was responsible for the phenotypic differences. |
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