Apparently balanced chromosome abnormalities are occasionally associated with mental retardation (MR). These balanced rearrangements may disrupt genes. However, the phenotype may also be caused by... Show moreApparently balanced chromosome abnormalities are occasionally associated with mental retardation (MR). These balanced rearrangements may disrupt genes. However, the phenotype may also be caused by small abnormalities present at the breakpoints or elsewhere in the genome. Conventional karyotyping is not instrumental for detecting small abnormalities because it only identifies genomic imbalances larger than 5-10 Mb. In contrast, high-resolution whole-genome arrays enable the detection of submicroscopic abnormalities in patients with apparently balanced rearrangements. Here, we report on the whole-genome analysis of 13 MR patients with previously detected balanced chromosomal abnormalities, five de novo, four inherited, and four of unknown inheritance, using Single Nucleotide Polymorphism (SNP) arrays. In all the cases, the patient had an abnormal phenotype. In one familial case and one unknown inheritance case, one of the parents had a phenotype which appeared identical to the patient's phenotype. Additional copy number variants (CNVs) were identified in eight patients. Three patients contained CNVs adjacent to one or either breakpoints. One of these patients showed four and two deletions near the breakpoints of a de novo pericentric inversion. In five patients we identified CNVs on chromosomes unrelated to the previously observed genomic imbalance. These data demonstrate that high-resolution array screening and conventional karyotyping is necessary to tie complex karyotypes to phenotypes of MR patients. (C) 2010 Elsevier Masson SAS. All rights reserved. Show less
Lemmers, R.J.L.F.; Vliet, P.J. van der; Klooster, R.; Sacconi, S.; Camano, P.; Dauwerse, J.G.; ... ; Maarel, S.M. van der 2010
Facioscapulohumeral muscular dystrophy (FSHD) is a common form of muscular dystrophy in adults that is foremost characterized by progressive wasting of muscles in the upper body. FSHD is associated... Show moreFacioscapulohumeral muscular dystrophy (FSHD) is a common form of muscular dystrophy in adults that is foremost characterized by progressive wasting of muscles in the upper body. FSHD is associated with contraction of D4Z4 macrosatellite repeats on chromosome 4q35, but this contraction is pathogenic only in certain "permissive" chromosomal backgrounds. Here, we show that FSHD patients carry specific single-nucleotide polymorphisms in the chromosomal region distal to the last D4Z4 repeat. This FSHD-predisposing configuration creates a canonical polyadenylation signal for transcripts derived from DUX4, a double homeobox gene of unknown function that straddles the last repeat unit and the adjacent sequence. Transfection studies revealed that DUX4 transcripts are efficiently polyadenylated and are more stable when expressed from permissive chromosomes. These findings suggest that FSHD arises through a toxic gain of function attributable to the stabilized distal DUX4 transcript. Show less
We have characterized a de novo complex rearrangement of the long arm of chromosome 7 in a female patient with moderate mental retardation (MR), anxiety disorder, and autistic features. G-banding... Show moreWe have characterized a de novo complex rearrangement of the long arm of chromosome 7 in a female patient with moderate mental retardation (MR), anxiety disorder, and autistic features. G-banding suggested a de novo paracentric inversion 46,XX,inv-(7) (q31.3q34). However, SNP-array analysis, showed a +/-10 Mb, 7q21.11-q21.3 deletion in the paternal chromosome. Subsequent FISH analysis with BAC/PAC clones in the 7q21-q35 region confirmed this deletion. However, the expected paracentric inversion turned out to be an intra-chromosomal insertion of the 7q31.31-q35 fragment into band 7q21.3, disrupting the predicted gene C7orf58 in band 7q31.31. Seven other patients have been previously reported with a deletion of 7q21.1-q21.3. Although there is an overlap in phenotype between our patient and these patients, none of them has been described with anxiety disorder and/or autistic features. Therefore we suggest that disruption of the C7orf58 gene might contribute to the anxiety disorder, and autistic features in our patient. (C) 2010 Wiley-Liss, Inc. Show less
We have characterized a de novo complex rearrangement of the long arm of chromosome 7 in a female patient with moderate mental retardation (MR), anxiety disorder, and autistic features. G-banding... Show moreWe have characterized a de novo complex rearrangement of the long arm of chromosome 7 in a female patient with moderate mental retardation (MR), anxiety disorder, and autistic features. G-banding suggested a de novo paracentric inversion 46,XX,inv(7)(q31.3q34). However, SNP-array analysis, showed a +/-10 Mb, 7q21.11-q21.3 deletion in the paternal chromosome. Subsequent FISH analysis with BAC/PAC clones in the 7q21-q35 region confirmed this deletion. However, the expected paracentric inversion turned out to be an intra-chromosomal insertion of the 7q31.31-q35 fragment into band 7q21.3, disrupting the predicted gene C7orf58 in band 7q31.31. Seven other patients have been previously reported with a deletion of 7q21.1-q21.3. Although there is an overlap in phenotype between our patient and these patients, none of them has been described with anxiety disorder and/or autistic features. Therefore we suggest that disruption of the C7orf58 gene might contribute to the anxiety disorder, and autistic features in our patient. Show less
Lemmers, R.J.L.F.; Vliet, P.J. van der; Klooster, R.; Sacconi, S.; Camano, P.; Dauwerse, J.G.; ... ; Maarel, S.M. van der 2010
Facioscapulohumeral muscular dystrophy (FSHD) is a common form of muscular dystrophy in adults that is foremost characterized by progressive wasting of muscles in the upper body. FSHD is associated... Show moreFacioscapulohumeral muscular dystrophy (FSHD) is a common form of muscular dystrophy in adults that is foremost characterized by progressive wasting of muscles in the upper body. FSHD is associated with contraction of D4Z4 macrosatellite repeats on chromosome 4q35, but this contraction is pathogenic only in certain "permissive" chromosomal backgrounds. Here, we show that FSHD patients carry specific single-nucleotide polymorphisms in the chromosomal region distal to the last D4Z4 repeat. This FSHD-predisposing configuration creates a canonical polyadenylation signal for transcripts derived from DUX4, a double homeobox gene of unknown function that straddles the last repeat unit and the adjacent sequence. Transfection studies revealed that DUX4 transcripts are efficiently polyadenylated and are more stable when expressed from permissive chromosomes. These findings suggest that FSHD arises through a toxic gain of function attributable to the stabilized distal DUX4 transcript. Show less
