Myotubular Myopathy in a girl with a deletion of Xq27-q28 and unbalanced X inactivation assigns the MTM1 gene to a 600-kb region
- Laboratoire de Genetique Molecularire des Eucaryotes du CNRS, INSERM U184, Strasbourg (France)
- Laboratoire de Genetique, CHRU, Nancy (France)
- INSERM U153, Paris (France)
- CHRU, Dijon (France)
- Institut for Humangenetik, Lubeck (France)
A young girl with a clinically moderate form of myotubular myopathy was found to carry a cytogenetically detectable deletion in Xq27-q28. The deletion had occurred de novo on the paternal X chromosome. It encompasses the fragile X (FRAXA) and Hunter syndrome (IDS) loci, and the DXS304 and DXS455 markers, in Xq27.3 and proximal Xq28. Other loci from the proximal half of Xq28 (DXS49, DXS256, DXS258, DXS305, and DXS497) were found intact. As the X-linked myotubular myopathy locus (MTM1) was previously mapped to Xq28 by linkage analysis, the present observation suggested that MTM1 is included in the deletion. However, a significant clinical phenotype is unexpected in a female MTM1 carrier. Analysis of inactive X-specific methylation at the androgen receptor gene showed that the deleted X chromosome was active in {approximately}80% of leukocytes. Such unbalanced inactivation may account for the moderate MTM1 phenotype and for the mental retardation that later developed in the patient. This observation is discussed in relation to the hypothesis that a locus modulating X inactivation may lie in the region. Comparison of this deletion with that carried by a male patient with a severe Hunter syndrome phenotype but no myotubular myopathy, in light of recent linkage data on recombinant MTM1 families, led to a considerable refinement of the position of the MTM1 locus, to a region of {approximately}600 kb, between DXS304 and DXS497. 46 refs., 4 figs.
- OSTI ID:
- 75451
- Journal Information:
- American Journal of Human Genetics, Journal Name: American Journal of Human Genetics Journal Issue: 5 Vol. 56; ISSN AJHGAG; ISSN 0002-9297
- Country of Publication:
- United States
- Language:
- English
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