Molecular characterization of FRAXE-positive subjects with mental impairment in two unrelated Italian families

Silvia Russo, Angelo Selicorni, Maria Francesca Bedeschi, Federica Natacci, Patrizia Viziello, Renato Fortuna, Giovanni Pagani, Leda Dalprà, Lidia Larizza

Research output: Contribution to journalArticlepeer-review


The FRAXE fragile site, 600 Kb distal to the more common FRAXA, has been reported to be expressed in subjects with mild nonsyndromal mental retardation. Amplification of more than 200 GCC repeats associated with methylation of the adjacent CpG island at Xq28 is responsible for FRAXE fragility. We describe two unrelated, mentally retarded males identified during a screening for fragile X syndrome. Both index cases underwent FRAXE molecular analysis, following cytogenetic expression of the fra X site and negative FRAXA test. In family 1, we were able to investigate other 13 subjects over three generations, identifying two additional FRAXE-positive males, one with a fully mutated allele and one with a mosaic genotype. Detailed evaluation of physical traits and psychometric tests was performed on three retarded males from family 1 and the propositus from family 2. All of them were found to lack a definite phenotype, and showed different degrees of mental retardation. Slight mental retardation was evident in the mosaic male, suggesting that methylation might be an important determinant of mental impairment.

Original languageEnglish
Pages (from-to)304-308
Number of pages5
JournalAmerican Journal of Medical Genetics
Issue number3
Publication statusPublished - Jan 23 1998


  • Clinical phenotype
  • Mental impairment
  • Mosaic genotype
  • Psychometric test

ASJC Scopus subject areas

  • Genetics(clinical)


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