title: Clinical and molecular cytogenetic characterization of two patients with non-mutational aberrations of the FMR2 gene.
abstract: We report on two patients; a female having mild mental retardation (MR) with a balanced translocation, 46,XX,t(X;15)(q28;p11.2), and a male diagnosed as having mucopolysaccharidosis type II (MPS II or Hunter syndrome) with atypical early-onset MR and a normal male karyotype. Molecular cytogenetic analyses, including fluorescence in situ hybridization and array-based comparative genomic hybridization using an in-house X-tiling array, revealed that first patient to have a breakpoint at Xq28 lying within the FMR2 gene and the second to have a small deletion at Xq28 including part of FMR2 together with the IDS gene responsible for MPS II. In Patient 1, X-chromosome inactivation predominantly occurred in the normal X in her lymphocytes, suggesting that her MR might be explained by a disruption of the FMR2 gene on der(X) t(X;15) concomitant with the predominant inactivation of the intact FMR2 gene in another allele. We compared phenotypes of Patient 2 with those of MPS II cases with deletion of the IDS gene alone reported previously, suggesting that the early-onset MR might be affected by the additional deletion of FMR2.
authors.affiliation: Department of Molecular Cytogenetics, Medical Research Institute and Graduate School of Biomedical Science, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Shozo
authors.initials: S
authors.lastname: Honda
authors.forename: Shin
authors.initials: S
authors.lastname: Hayashi
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Kato
authors.forename: Yo
authors.initials: Y
authors.lastname: Niida
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Hayasaka
authors.forename: Torayuki
authors.initials: T
authors.lastname: Okuyama
authors.forename: Issei
authors.initials: I
authors.lastname: Imoto
authors.forename: Shuki
authors.initials: S
authors.lastname: Mizutani
authors.forename: Johji
authors.initials: J
authors.lastname: Inazawa
mesh_terms: D002675:Child, Preschool; D020732:Cytogenetic Analysis; D005260:Female; D006801:Humans; D007223:Infant; D008607:Intellectual Disability / Q000235:genetics*; D008297:Male; D016532:Mucopolysaccharidosis II / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D014178:Translocation, Genetic
chemical_list: C099930:AFF2 protein, human; D009687:Nuclear Proteins; D015534:Trans-Activators