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J Med Genet 1999;36:754-758 doi:10.1136/jmg.36.10.754
  • Original article

Two unrelated patients with inversions of the X chromosome and non-specific mental retardation: physical and transcriptional mapping of their common breakpoint region in Xq13.1

  1. Laurent Villard*,a,
  2. Sylvain Briault*,b,
  3. Anne-Marie Lossia,
  4. Christine Paringauxb,
  5. Jérôme Belougnea,
  6. Laurence Colleauxa,
  7. D R Pincusc,
  8. E Woollattd,
  9. James Lespinassee,
  10. Arnold Munnichf,
  11. Claude Moraineb,
  12. Michel Fontèsa,
  13. Jozef Geczd,g
  1. aINSERM U491, Université de la Méditerranée, Faculté de Médecine La Timone, 27 Bd J Moulin, 13385 Marseille, France, bService de Génétique, Hôpital Bretonneau, 2 Bd Tonnellé, 37044 Tours, France, cAllamanda Medical Centre, Southport, Australia, dDepartment of Cytogenetics and Molecular Genetics, Women’s and Children’s Hospital, Adelaide, Australia, eLaboratoire de Cytogénétique, Centre Hospitalier de Chambery, 73000 Chambery, France, fDépartement de Génétique, Hôpital Necker-Enfants Malades, 149 rue de Sèvres, 75743 Paris Cedex 15, France, gDepartment of Paediatrics, University of Adelaide, Adelaide, Australia.
  1. Dr Villard.
  • Revised 27 May 1999
  • Accepted 16 June 1999

Abstract

Two unrelated mildly retarded males with inversions of the X chromosome and non-specific mental retardation (MRX) are described. Case 1 has a pericentric inversion 46,Y,inv(X)(p11.1q13.1) and case 2 a paracentric inversion 46,Y,inv(X) (q13.1q28). Both male patients have severe learning difficulties. The same chromosomal abnormalities were found in their mothers who are intellectually normal. Fluorescence in situ hybridisation mapping showed a common area of breakage of each of the inverted chromosomes in Xq13.1 near DXS131 and DXS162. A detailed long range restriction map of the breakpoint region was constructed using YAC, PAC, and cosmid clones. We show that the two inverted chromosomes break within a short 250 kb region. Moreover, a group of ESTs corresponding to an as yet uncharacterised gene was mapped to the same critical interval. We hypothesise that the common inversion breakpoint region of the two cases in Xq13.1 may contain a new MRX gene.

Footnotes

  • ↵* The first two authors contributed equally to this work

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