Cases reported "Chromosome Breakage"

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1/182. Xp deletions associated with autism in three females.

    We report eight females with small deletions of the short arm of the x chromosome, three of whom showed features of autism. Our results suggest that there may be a critical region for autism in females with Xp deletions between the pseudoautosomal boundary and DXS7103. We hypothesise that this effect might be due either to the loss of function of a specific gene within the deleted region or to functional nullisomy resulting from X inactivation of the normal x chromosome. ( info)

2/182. Fibroblast growth factor homologous factor 2 (FHF2): gene structure, expression and mapping to the Borjeson-Forssman-Lehmann syndrome region in Xq26 delineated by a duplication breakpoint in a BFLS-like patient.

    Borjeson-Forssman-Lehmann syndrome (BFLS) is a syndromal X-linked mental retardation, which maps by linkage to the q26 region of the human x chromosome. We have identified a male patient with BFLS-like features and a duplication, 46,Y,dup(X)(q26q28), inherited from his phenotypically normal mother. fluorescence in situ hybridisation using yeast artificial chromosome clones from Xq26 localised the duplication breakpoint to an approximately 400-kb interval in the Xq26.3 region between DXS155 and DXS294/DXS730. database searches and analysis of available genomic dna sequence from the region revealed the presence of the fibroblast growth factor homologous factor gene, FHF2, within the duplication breakpoint interval. The gene structure of FHF2 was determined and two new exons were identified, including a new 5' end exon, 1B. FHF2 is a large gene extending over approximately 200 kb in Xq26.3 and is composed of at least seven exons. It shows tissue-specific alternative splicing and alternative transcription starts. Northern blot hybridisation showed highest expression in brain and skeletal muscle. The FHF2 gene localisation and tissue-specific expression pattern suggest it to be a candidate gene for familial cases of the BFLS syndrome and other syndromal and non-specific forms of X-linked mental retardation mapping to the region. ( info)

3/182. Campomelic syndrome and deletion of SOX9.

    The human SOX9 gene, located in chromosome region 17q24.1-25.1, encodes a transcription factor involved in chondrogenesis and testis development. Mutations in this gene cause campomelic syndrome (CMPS) with autosomal sex reversal. Here we describe an infant girl with CMPS and an interstitial deletion on the long arm of chromosome 17 (46,X,del(17)(q23.3q24.3). The extent of SOX9 deletion on one chromosome 17 was defined using unique sequence fluorescent in situ hybridization probes. This is the first report of a patient with CMPS bearing a complete deletion of one SOX9 gene, and as such is the strongest evidence to date for dose-dependent action of the SOX9 protein in normal chondrogenesis. ( info)

4/182. Two patients with novel BCR/ABL fusion transcripts (e8/a2 and e13/a2) resulting from translocation breakpoints within BCR exons.

    We have identified novel BCR-ABL mRNA fusions by RT-PCR in two patients with Philadelphia (Ph) chromosome positive leukaemia. Sequencing revealed in-frame fusions consisting of part of BCR exon e8 spliced to ABL exon a2 in one patient and part of BCR exon e13 spliced to ABL exon a2 in the other. The breaks within BCR exons e8 and e13 did not conform to consensus splice sites, suggesting that the aberrant fusion mRNAs may have arisen as a result of translocation breakpoints at these sites. This was confirmed by genomic dna bubble PCR for the second patient. These data show that BCR-ABL translocation breakpoints can occasionally occur within coding exons. ( info)

5/182. Neocentromere at 13q32 in one of two stable markers derived from a 13q21 break.

    A 10-month-old girl with psychomotor retardation, microcephaly, bilateral microphthalmia, and postaxial polydactyly of the feet was karyotyped using banding techniques and (single or dual color) fluorescent in situ hybridization (FISH) with four probes: D13Z1/D21Z1, pancentromeric, pantelomeric, and a mix of 13q subtelomeric and 13/21 alphoid repeats. She was found to have a 47-chromosome karyotype in which a normal 13 was replaced by two stable markers derived from a breakpoint at 13q21.1, namely a del(13)(q21.1) and an isofragment(13) (qter-->q21.1::q21.1-->qter). The latter had a single C-negative but Cd-positive primary constriction at 13q32 which, however, was not obvious in about 12% of the cells. FISH studies showed that the small 13q- had the 13-centromere and a 13q telomere (as shown for a specific 13q subtelomeric signal) onto the broken end whereas the isofragment lacked alphoid signals but had 13q subtelomeric sequences on both ends. Parental karyotypes were normal. The patient's rearrangement represents the eighth chromosome-13-derived marker with a nonalphoid neocentromere located at 13q. All in all, such neocentromeres have been described in 29 markers derived from chromosomes 2, 3, 8-11, 13-15, 20, and Y, and plausibly result from the epigenetic activation of a latent centromere, which may even be a telomere with neocentric activity. The 13q telomere found in the del(13q) was probably captured from the homologous chromosome. ( info)

6/182. A locus for isolated cleft palate, located on human chromosome 2q32.

    We present evidence for the existence of a novel chromosome 2q32 locus involved in the pathogenesis of isolated cleft palate. We have studied two unrelated patients with strikingly similar clinical features, in whom there are apparently balanced, de novo cytogenetic rearrangements involving the same region of chromosome 2q. Both children have cleft palate, facial dysmorphism, and mild learning disability. Their karyotypes were originally reported as 46, XX, t(2;7)(q33;p21) and 46, XX, t(2;11)(q33;p14). However, our molecular cytogenetic analyses localize both translocation breakpoints to a small region between markers D2S311 and D2S116. This suggests that the true location of these breakpoints is 2q32 rather than 2q33. To obtain independent support for the existence of a cleft-palate locus in 2q32, we performed a detailed statistical analysis for all cases in the human cytogenetics database of nonmosaic, single, contiguous autosomal deletions associated with orofacial clefting. This revealed 2q32 to be one of only three chromosomal regions in which haploinsufficiency is significantly associated with isolated cleft palate. In combination, our data provide strong evidence for the location at 2q32 of a gene that is critical to the development of the secondary palate. The close proximity of these two translocation breakpoints should also allow rapid progress toward the positional cloning of this cleft-palate gene. ( info)

7/182. Partial monosomy of distal 10q: three new cases and a review.

    We report on 3 patients with partial deletions of the long arm of chromosome 10-46,XY,del (10)(q26.2), 46,XX,del(10) (q25.3q26.3) or 46,XX,del(10)(q26.1), and 46,XX,del (10)(q26.1). They are compared with other known cases with interstitial or terminal deletions involving chromosome bands 10q25 or q26. Unique manifestations are identified, including scoliosis and a severe behavior disorder with attention deficit and hyperactivity in a 12-year-old boy as well as patchy alopecia in a 6-year-old patient. ( info)

8/182. Jumping translocations involving 11q in a non-Hodgkin lymphoma.

    This paper presents the results of a cytogenetic analysis in an 11-year-old boy with non-Hodgkin lymphoma. The investigation was performed on slides obtained from short-term culture of lymph node cells. The analyses revealed an abnormal clone with loss of Y, gain of an x chromosome, t(3;22), trisomy 11, and three cytogenetically-related subclones with jumping translocations involving 11q13 as the common breakpoint region. This region is an unusual site of chromosome breakage in jumping translocations, and has not been reported thus far. Contrary to most published reports, the jumping translocation in our patient is associated with long survival. ( info)

9/182. Chromosome 16 inversion-associated translocation: two new cases.

    Two patients with chromosome 16 inversion-associated translocation were studied with conventional cytogenetic and fluorescence in situ hybridization (FISH) techniques. The same chromosome 16 was involved in inversion and translocation in both patients. The chromosome translocation breakpoint was located within the heterochromatin of chromosome 16 but outside the alpha satellite domain in the t(10;16) of the first patient, whereas it was outside the heterochromatin area in the second case with t(1;16). These two types of rearrangements may be due to different mechanisms and illustrate the possible difficulties in recognizing the chromosome 16 inversion without FISH studies. ( info)

10/182. Alu and translisin recognition site sequences flanking translocation sites in a novel type of chimeric bcr-abl transcript suggest a possible general mechanism for bcr-abl breakpoints.

    BACKGROUND AND OBJECTIVE: We further characterized a novel type of chimeric BCR-ABL mRNA transcript detected in a patient with philadelphia chromosome positive (Ph ) chronic myeloid leukemia (CML). DESIGN AND methods: We used reverse-transcription polymerase chain reaction (RT-PCR) and sequence analysis of the fusion region of the amplified cDNA fragment. Western analysis was performed on total protein. RESULTS: Part of exon e8 of the BCR gene was joined to an intronic sequence of ABL intron Ib spliced on exon a2 of the ABL gene, giving rise to an in-frame e8-int-a2 BCR-ABL transcript. Only part of exon 8 of the BCR gene (e8) (intra-exonic break) was retained. The consequent BCR-int-ABL transcript was translated into a BCR-ABL protein of 1804 amino acid residues with a molecular mass of 197.5 kilodaltons (kDa) called p200 BCR-ABL. The 3' part of bcr exon 8 recombined within or alongside alu elements at the additional sites. Sequence motifs similar to consensus binding sites of the lymphoid-associated TRAX and translisin proteins were present on both participating strands at 22q11 and 9q34 recombination sites, respectively. No differences in clinical or laboratory findings at diagnosis were found between this patient and CML patients with bcr-abl fusion. INTERPRETATION AND CONCLUSIONS: The presence of Alu sequences and of the translisin binding motif on both sides of the breaks in this novel translocation suggests a possible general mechanism of molecular recombination in CML patients. ( info)
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