Ring chromosome

About: Ring chromosome is a research topic. Over the lifetime, 1546 publications have been published within this topic receiving 31061 citations. The topic is also known as: supernumerary circular chromosome.

Hepatosplenic γδ T-cell lymphoma with ring chromosome 7, an isochromosome 7q equivalent clonal chromosomal aberration

Abstract: Hepatosplenic T-cell lymphoma is a rare, clinically aggressive lymphoma. Most cases represent a neoplasm of mature non-activated gammadelta T cells. Isochromosome 7q i(7)(q10) is thought to be the primary cytogenetic abnormality of this disease. In this paper, we describe a hepatosplenic gammadelta T-cell lymphoma case, with clonal ring chromosome 7 exemplifying an isochromosome 7q equivalent clonal aberration. A 62-year-old female patient presented with thrombocytopenia, isolated hepatosplenomegaly, and extremely high levels of LDH. Bone marrow work-up demonstrated a sinusoidal cytotoxic T-cell infiltrate with blastic features, while molecular studies verified monoclonal rearrangement for both TCR gamma and TCR delta genes. Cytogenetics revealed clonal abnormalities including ring chromosome 7, trisomy 8, and der(19), while FISH analysis detected 7q amplification with partial deletion of 7p in ring chromosome 7. To the best of our knowledge, this is the first reported T-cell lymphoma case with ring chromosome 7.

Ring chromosome 22 and neurofibromatosis type II: proof of two-hit model for the loss of the NF2 gene in the development of meningioma.

Abstract: Zirn B, Arning L, Bartels I, Shoukier M, Hoffjan S, Neubauer B, Hahn A. Ring chromosome 22 and neurofibromatosis type II: proof of two-hit model for the loss of the NF2 gene in the development of meningioma. Carriers of a ring chromosome 22 are mentally retarded and show variable facial dysmorphism. They may also present with features of neurofibromatosis type II (NF2) such as vestibular schwannomas and multiple meningiomas. In these cases, tumourigenesis has been suspected to be caused by the loss of both alleles of the NF2 gene, a tumour suppressor localized in 22q12.2. Here, we describe an 18-year-old patient with constitutional ring chromosome 22 and mental retardation who developed rapid-onset spastic paraparesis at the age of 15 years. The causative spinal meningioma at the level of T3, which compressed the spinal cord, was surgically removed, and the patient regained ambulation. Array comparative genomic hybridization (array CGH) and multiplex ligation-dependent probe amplification (MLPA) analyses in blood revealed a terminal deletion in 22q13.32, not comprising the NF2 gene. In tumour tissue, loss of the whole ring chromosome 22 including one NF2 gene due to mitotic instability constituted the likely first hit, while a point mutation in the other allele of the NF2 gene (c.784C>T, p.R262X) was shown as second hit. We review all cases from the literature and suggest clinical guidelines for surveillance of patients with ring chromosome 22.

Q-banding of chromosomes in human spontaneous abortions

Abstract: Chromosome studies of 242 spontaneous abortions were carried out by Q-banding technique. The abortuses were selected for study because they were phenotypically abnormal, had not progressed beyond 12 weeks development, or were from women with repeated abortions. Chromosome anomalies were found in 126 (52%) of the abortuses. Of these, 71 (56%) were trisomies. Trisomies were found for all the autosomes except Nos. 1, 3, 5, 11, 17 and 18. Triploidy was the second commonest anomaly in this series, making up 26 (21%) of the total anomalies. About 70% of these had an XXY sex chromosome complement. Only 16 (13%) of the abortuses had X monosomy, a lower frequency than would be expected in an unselected study. Tetraploidy was found in 8 abortuses and the 5 remaining specimens had various anomalies. These included 3 translocations, a trisomy 21,X monosomy and a ring chromosome 13. Except for the greater frequency of XXY than XXX sex chromosomes in the triploids, there was no evidence of a distortion of the sex ratio...

Prenatal diagnosis of a mosaic extra structurally abnormal chromosome by spectral karyotyping.

Abstract: A de novo mosaic extra structurally abnormal chromosome (ESAC) was detected in 33 per cent of cultured amniotic fluid cells from a pregnant woman. Neither Q-banding nor fluorescence in situ hybridization (FISH) employing a DNA probe for nucleolar organizer region demonstrated the presence of satellites on the ESAC. Spectral karyotyping (SKY) was performed in this prenatal case and led to a quick and accurate determination of the ESAC as chromosome 14 in origin. The SKY finding was confirmed by conventional FISH analysis using a chromosome 14 specific painting probe. Subsequent hybridizations with a centromeric probe and a 14q subtelomeric probe were also performed to further characterize the ESAC. Absence of (TTAGGG)n sequence on the ESAC, determined postnatally, suggested it is a ring chromosome 14. Genetic counselling concerning these findings was provided to the parents who chose to continue the pregnancy. The male infant had no apparent abnormal phenotype at birth.