Clinical and molecular cytogenetic characterization of two patients with non-mutational aberrations of the FMR2 gene.
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.
Honda
Shozo
S
Department of Molecular Cytogenetics, Medical Research Institute and Graduate School of Biomedical Science, Tokyo Medical and Dental University, Tokyo, Japan.
Hayashi
Shin
S
Kato
Mitsuhiro
M
Niida
Yo
Y
Hayasaka
Kiyoshi
K
Okuyama
Torayuki
T
Imoto
Issei
I
Mizutani
Shuki
S
Inazawa
Johji
J
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
C099930:AFF2 protein, human; D009687:Nuclear Proteins; D015534:Trans-Activators