title: Folate-sensitive fragile site FRA10A is due to an expansion of a CGG repeat in a novel gene, FRA10AC1, encoding a nuclear protein.
abstract: Fragile sites appear visually as nonstaining gaps on chromosomes that are inducible by specific cell culture conditions. Expansion of CGG/CCG repeats has been shown to be the molecular basis of all five folate-sensitive fragile sites characterized molecularly so far, i.e., FRAXA, FRAXE, FRAXF, FRA11B, and FRA16A. In the present study we have refined the localization of the FRA10A folate-sensitive fragile site by fluorescence in situ hybridization. Sequence analysis of a BAC clone spanning FRA10A identified a single, imperfect, but polymorphic CGG repeat that is part of a CpG island in the 5'UTR of a novel gene named FRA10AC1. The number of CGG repeats varied in the population from 8 to 13. Expansions exceeding 200 repeat units were methylated in all FRA10A fragile site carriers tested. The FRA10AC1 gene consists of 19 exons and is transcribed in the centromeric direction from the FRA10A repeat. The major transcript of approximately 1450 nt is ubiquitously expressed and codes for a highly conserved protein, FRA10AC1, of unknown function. Several splice variants leading to alternative 3' ends were identified (particularly in testis). These give rise to FRA10AC1 proteins with altered COOH-termini. Immunofluorescence analysis of full-length, recombinant EGFP-tagged FRA10AC1 protein showed that it was present exclusively in the nucleoplasm. We show that the expression of FRA10A, in parallel to the other cloned folate-sensitive fragile sites, is caused by an expansion and subsequent methylation of an unstable CGG trinucleotide repeat. Taking advantage of three cSNPs within the FRA10AC1 gene we demonstrate that one allele of the gene is not transcribed in a FRA10A carrier. Our data also suggest that in the heterozygous state FRA10A is likely a benign folate-sensitive fragile site.
authors.affiliation: Department of Biology, University of Crete, and Institute of Molecular Biology and Biotechnology(IMBB), Foundation of Research and Technology (FORTH-GR), P.O. Box 2208, 714 09 Heraklion, Crete, Greece.
authors.forename: Theologia
authors.initials: T
authors.lastname: Sarafidou
authors.forename: Christina
authors.initials: C
authors.lastname: Kahl
authors.forename: Isabel
authors.initials: I
authors.lastname: Martinez-Garay
authors.forename: Marie
authors.initials: M
authors.lastname: Mangelsdorf
authors.forename: Stefan
authors.initials: S
authors.lastname: Gesk
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Baker
authors.forename: Maria
authors.initials: M
authors.lastname: Kokkinaki
authors.forename: Polly
authors.initials: P
authors.lastname: Talley
authors.forename: Edna L
authors.initials: EL
authors.lastname: Maltby
authors.forename: Lisa
authors.initials: L
authors.lastname: French
authors.forename: Lana
authors.initials: L
authors.lastname: Harder
authors.forename: Bernd
authors.initials: B
authors.lastname: Hinzmann
authors.forename: Carlo
authors.initials: C
authors.lastname: Nobile
authors.forename: Kathy
authors.initials: K
authors.lastname: Richkind
authors.forename: Merran
authors.initials: M
authors.lastname: Finnis
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Deloukas
authors.forename: Grant R
authors.initials: GR
authors.lastname: Sutherland
authors.forename: Kerstin
authors.initials: K
authors.lastname: Kutsche
authors.forename: Nicholas K
authors.initials: NK
authors.lastname: Moschonas
authors.forename: Reiner
authors.initials: R
authors.lastname: Siebert
authors.forename: Jozef
authors.initials: J
authors.lastname: Gécz
mesh_terms: D000483:Alleles; D017398:Alternative Splicing / Q000235:genetics; D000595:Amino Acid Sequence; D043283:Chromosome Fragile Sites / Q000235:genetics*; D002873:Chromosome Fragility / Q000235:genetics*; D019175:DNA Methylation; D006801:Humans; D042581:Intranuclear Space / Q000378:metabolism; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D009928:Organ Specificity / Q000235:genetics; D016415:Sequence Alignment; D014158:Transcription, Genetic / Q000235:genetics; D019680:Trinucleotide Repeat Expansion / Q000235:genetics*; D018911:Trinucleotide Repeats / Q000235:genetics*
chemical_list: C496403:FRA10AC1 protein, human; D009687:Nuclear Proteins