title: Finding FMR1 mosaicism in Fragile X syndrome.
abstract: OBJECTIVE
  Almost all patients with Fragile X Syndrome (FXS) exhibit a CGG repeat expansion (full mutation) in the Fragile Mental Retardation 1 gene (FMR1). Here, the authors report five unrelated males with FXS harboring a somatic full mutation/deletion mosaicism.
  
  
  METHODS
  Mutational profiles were only elucidated by using a combination of molecular approaches (CGG-based PCR, Sanger sequencing, MS-MLPA, Southern blot and mPCR).
  
  
  RESULTS
  Four patients exhibited small deletions encompassing the CGG repeats tract and flanking regions, whereas the remaining had a larger deletion comprising at least exon 1 and part of intron 1 of FMR1 gene. The presence of a 2-3 base pairs microhomology in proximal and distal non-recurrent breakpoints without scars supports the involvement of microhomology mediated induced repair (MMBIR) mechanism in three small deletions.
  
  
  CONCLUSIONS
  The authors data highlights the importance of using different research methods to elucidate atypical FXS mutational profiles, which are clinically undistinguishable and may have been underestimated.
authors.affiliation: a Department of Genetics , State University of Rio de Janeiro , Rio de Janeiro , Brazil.
authors.forename: Thaís Fernandez
authors.initials: TF
authors.lastname: Gonçalves
authors.affiliation: a Department of Genetics , State University of Rio de Janeiro , Rio de Janeiro , Brazil.
authors.forename: Jussara Mendonça
authors.initials: JM
authors.lastname: dos Santos
authors.affiliation: a Department of Genetics , State University of Rio de Janeiro , Rio de Janeiro , Brazil.
authors.forename: Andressa Pereira
authors.initials: AP
authors.lastname: Gonçalves
authors.affiliation: b Department of Biochemistry and Molecular Medicine , UC Davis School of Medicine, University of California, Davis , Sacramento , CA , USA.|c Davis MIND Institute , Sacramento , CA , USA.
authors.forename: Flora
authors.initials: F
authors.lastname: Tassone
authors.affiliation: b Department of Biochemistry and Molecular Medicine , UC Davis School of Medicine, University of California, Davis , Sacramento , CA , USA.
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Mendoza-Morales
authors.affiliation: d Clinical Genetics Service , IPPMG, Federal University of Rio de Janeiro , Rio de Janeiro , Brazil.
authors.forename: Márcia Gonçalves
authors.initials: MG
authors.lastname: Ribeiro
authors.affiliation: d Clinical Genetics Service , IPPMG, Federal University of Rio de Janeiro , Rio de Janeiro , Brazil.
authors.forename: Evelyn
authors.initials: E
authors.lastname: Kahn
authors.affiliation: e Pedro Ernesto University Hospital , State University of Rio de Janeiro , Rio de Janeiro , Brazil.
authors.forename: Raquel
authors.initials: R
authors.lastname: Boy
authors.affiliation: a Department of Genetics , State University of Rio de Janeiro , Rio de Janeiro , Brazil.
authors.forename: Márcia Mattos Gonçalves
authors.initials: MM
authors.lastname: Pimentel
authors.affiliation: a Department of Genetics , State University of Rio de Janeiro , Rio de Janeiro , Brazil.
authors.forename: Cíntia Barros
authors.initials: CB
authors.lastname: Santos-Rebouças
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D005091:Exons; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics*; D005600:Fragile X Syndrome / Q000235:genetics* / Q000473:pathology; D006801:Humans; D007438:Introns; D008297:Male; D009030:Mosaicism; D009154:Mutation; D017384:Sequence Deletion; D019680:Trinucleotide Repeat Expansion
chemical_list: D051860:Fragile X Messenger Ribonucleoprotein 1; C497683:FMR1 protein, human
keywords: FMR1 gene; Fragile X syndrome; copy number variation; deletion; mosaicism