Mapping of MRX81 in Xp11.2-Xq12 suggests the presence of a new gene involved in nonspecific X-linked mental retardation

Ida Annunziata, Carmela Lanzara, Ivan Conte, Alberto Zullo, Valerio Ventruto, Maria Michela Rinaldi, Michele D'Urso, Giorgio Casari, Alfredo Ciccodicola, Maria Giuseppina Miano

Research output: Contribution to journalArticlepeer-review


X-linked nonspecific mental retardation (MRX) accounts for ∼25% of mental retardation in males. A number of MRX loci have been mapped on the X chromosome, reflecting the complexity of gene action in central nervous system (CNS) specification and function. Eleven MRX genes have been identified, but many other causative loci remain to be refined to the single gene level. In 21 MRX families, the causative gene is located in the pericentromeric region; and we report here the identification by linkage analysis of a further such locus, MRX81. The new MRX locus was identified by two- and multi-point parametric analysis carried out on a large Italian family. Tight linkage of MRX81 to DNA markers ALAS2, DXS991, and DXS7132 was observed with a maximum LOD score of 3.43. Haplotype construction delineates an MRX81 critical region of 8 cM, the smallest MRX pericentromeric interval so far described, between DXS1039 and DXS1216, and placing it in Xp11.2-Xq12. So far, automated sequencing of two candidates in the region, the MRX gene oligophrenin (OPHN1) and the brain-specific ephrinB1 (EFNB1) gene, in DNA from affected males excluded their candidacy for MRX81, suggesting a novel disease gene.

Original languageEnglish
Pages (from-to)217-222
Number of pages6
JournalAmerican Journal of Medical Genetics
Volume118 A
Issue number3
Publication statusPublished - Apr 30 2003


  • Linkage analysis
  • MRX
  • MRX81
  • Nonspecific X mental retardation
  • Xp11.2-Xq12

ASJC Scopus subject areas

  • Genetics(clinical)


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