BackgroundThe breakpoints and mechanisms of ring chromosome formation were studied and mapped in 14 patients.MethodsSeveral techniques were performed such as genome-wide array, MLPA (Multiplex Ligation-Dependent Probe Amplification) and FISH (Fluorescent in situ Hybridization).ResultsThe ring chromosomes of patients I to XIV were determined to be, respectively: r(3)(p26.1q29), r(4)(p16.3q35.2), r(10)(p15.3q26.2), r(10)(p15.3q26.13), r(13)(p13q31.1), r(13)(p13q34), r(14)(p13q32.33), r(15)(p13q26.2), r(18)(p11.32q22.2), r(18)(p11.32q21.33), r(18)(p11.21q23), r(22)(p13q13.33), r(22)(p13q13.2), and r(22)(p13q13.2). These rings were found to have been formed by different mechanisms, such as: breaks in both chromosome arms followed by end-to-end reunion (patients IV, VIII, IX, XI, XIII and XIV); a break in one chromosome arm followed by fusion with the subtelomeric region of the other (patients I and II); a break in one chromosome arm followed by fusion with the opposite telomeric region (patients III and X); fusion of two subtelomeric regions (patient VII); and telomere-telomere fusion (patient XII). Thus, the r(14) and one r(22) can be considered complete rings, since there was no loss of relevant genetic material. Two patients (V and VI) with r(13) showed duplication along with terminal deletion of 13q, one of them proved to be inverted, a mechanism known as inv-dup-del. Ring instability was detected by ring loss and secondary aberrations in all but three patients, who presented stable ring chromosomes (II, XIII and XIV).ConclusionsWe concluded that the clinical phenotype of patients with ring chromosomes may be related with different factors, including gene haploinsufficiency, gene duplications and ring instability. Epigenetic factors due to the circular architecture of ring chromosomes must also be considered, since even complete ring chromosomes can result in phenotypic alterations, as observed in our patients with complete r(14) and r(22).
BackgroundTrisomy 9p is one of the most common partial trisomies found in newborns. We report the clinical features and cytogenomic findings in five patients with different chromosome rearrangements resulting in complete 9p duplication, three of them involving 9p centromere alterations.MethodsThe rearrangements in the patients were characterized by G-banding, SNP-array and fluorescent in situ hybridization (FISH) with different probes.ResultsTwo patients presented de novo dicentric chromosomes: der(9;15)t(9;15)(p11.2;p13) and der(9;21)t(9;21)(p13.1;p13.1). One patient presented two concomitant rearranged chromosomes: a der(12)t(9;12)(q21.13;p13.33) and an psu i(9)(p10) which showed FISH centromeric signal smaller than in the normal chromosome 9. Besides the duplication 9p24.3p13.1, array revealed a 7.3 Mb deletion in 9q13q21.13 in this patient. The break in the psu i(9)(p10) probably occurred in the centromere resulting in a smaller centromere and with part of the 9q translocated to the distal 12p with the deletion 9q occurring during this rearrangement. Two patients, brother and sister, present 9p duplication concomitant to 18p deletion due to an inherited der(18)t(9;18)(p11.2;p11.31)mat.ConclusionsThe patients with trisomy 9p present a well-recognizable phenotype due to facial appearance, although the genotype-phenotype correlation can be difficult due to concomitant partial monosomy of other chromosomes. The chromosome 9 is rich in segmental duplication, especially in pericentromeric region, with high degree of sequence identity to sequences in 15p, 18p and 21p, chromosomes involved in our rearrangements. Thus, we suggest that chromosome 9 is prone to illegitimate recombination, either intrachromosomal or interchromosomal, which predisposes it to rearrangements, frequently involving pericentromeric regions.
BackgroundThe majority of Marfan syndrome (MFS) cases is caused by mutations in the fibrillin-1 gene (FBN1), mapped to chromosome 15q21.1. Only few reports on deletions including the whole FBN1 gene, detected by molecular cytogenetic techniques, were found in literature.ResultsWe report here on a female patient with clinical symptoms of the MFS spectrum plus craniostenosis, hypothyroidism and intellectual deficiency who presents a 1.9 Mb deletion, including the FBN1 gene and a complex rearrangement with eight breakpoints involving chromosomes 6, 12 and 15.DiscussionThis is the first report of MFS with a complex chromosome rearrangement involving a deletion of FBN1 and contiguous genes. In addition to the typical clinical findings of the Marfan syndrome due to FBN1 gene haploinsufficiency, the patient presents features which may be due to the other gene deletions and possibly to the complex chromosome rearrangement.
Gastric cancer is the third most frequent type of neoplasia and the second most important cause of death in the world. ACP01 is the first gastric adenocarcinoma cell line developed in Brazil. To evaluate chromosomal aberrations implicated in gastric carcinogenesis, we analysed three different passages (6th, 12th and 35th) of ACP01 cell line by fluorescence in situ hybridisation using chromosome 8 alpha-satellite probe. Most of the chromosome 8 alterations found involved a numerical increase of this chromosome. Chromosome 8 trisomy was detected in all cases, varying from 37% (6th passage) to 67% (35th passage), and chromosome 8 tetrasomy (also observed in all passages) varied from 2.5% (6th passage) to 30% (35th passage). The presence of five signals for chromosome 8 was observed in all passages with the highest frequency found in the 12th passage (20%). Our results confirm that trisomy of chromosome 8 is a common biological phenomenon in adenocarcinoma of stomach and can be used as a gastric mucosa malignancy marker. Although gastric tumours are frequent neoplasias, papers on their cytogenetics are scarce in the literature. It is, therefore, necessary to conduct new studies aiming to identify peculiar genetic characteristics of a tumour, which might help in diagnosis and prognosis of this disease, besides allowing more accurate therapeutic conduct to be established.
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