Screening for FMR1 and FMR2 mutations in 222 individuals from Spanish special schools

Identification of a case of FRAXE-associated mental retardation

Montserrat Milà, Aurora Sànchez, Cèlia Badenas, Carme Brun, Dolores Jiménez, M. Paula Villa, Sergi Castellví-Bel, Xavier P. Estivill

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

Fragile X syndrome is the most common inherited form of familial mental retardation. It results from a (CGG)(n) trinucleotide expansion in the FMR1 gene leading to the typical Martin-Bell phenotype. Clinical features vary depending on age and sex. Expansion of a (CCG)(n) repeat in the FMR2 gene corresponds to the FRAXE fragile site which lies distal to FRAXA and is also associated with mental retardation, but it is less frequent and lacks a consistent phenotype. Analysis of repeat expansions in these two genes allows the molecular diagnosis of these different entities. We report here the screening of the FRAXA and FRAXE mutations in 222 unrelated mentally retarded individuals attending Spanish special schools. PCR and/or Southern blotting methods were used. We detected full mutations in the FMR1 gene in 11 boys (4.9%) and 1 boy (0.5%) with a CCG)(n) repeat expansion in the FMR2 gene. The latter shows mild mental retardation with psychotic behaviour and no remarkable physical traits. Molecular studies revealed a mosaicism for methylation in the FMR2 gene. This case supports the observation that expansions greater than 100 repeats can be partially methylated and cause the phenotype.

Original languageEnglish
Pages (from-to)503-507
Number of pages5
JournalHuman Genetics
Volume100
Issue number5-6
DOIs
Publication statusPublished - 1997
Externally publishedYes

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Intellectual Disability
Mutation
Genes
Phenotype
Fragile X Syndrome
Mosaicism
Mentally Disabled Persons
Southern Blotting
Methylation
Polymerase Chain Reaction

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)

Cite this

Screening for FMR1 and FMR2 mutations in 222 individuals from Spanish special schools : Identification of a case of FRAXE-associated mental retardation. / Milà, Montserrat; Sànchez, Aurora; Badenas, Cèlia; Brun, Carme; Jiménez, Dolores; Paula Villa, M.; Castellví-Bel, Sergi; Estivill, Xavier P.

In: Human Genetics, Vol. 100, No. 5-6, 1997, p. 503-507.

Research output: Contribution to journalArticle

Milà, Montserrat ; Sànchez, Aurora ; Badenas, Cèlia ; Brun, Carme ; Jiménez, Dolores ; Paula Villa, M. ; Castellví-Bel, Sergi ; Estivill, Xavier P. / Screening for FMR1 and FMR2 mutations in 222 individuals from Spanish special schools : Identification of a case of FRAXE-associated mental retardation. In: Human Genetics. 1997 ; Vol. 100, No. 5-6. pp. 503-507.
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