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.

Sub-band deletion of 7q36.3 in a patient with ring chromosome 7: association with holoprosencephaly.

Abstract: We report on a patient with ring chromosome 7 analyzed by both high-resolution mid-prophase G-banding and fluorescence in situ hybridization (FISH) resolving a subband deletion of 7q36.3 associated with the clinical manifestation of holoprosencephaly (HPE).

7 Developmentally Programmed Healing of Chromosomes

Abstract: Chromosome healing is a developmentally programmed process in diverse eukaryotes. In 1887, Boveri reported that in the parasitic nematode Parascaris equorum, the chromosomes in the presomatic cells of early embryos became fragmented and heterochromatin was eliminated. Similar findings were made for other parasitic nematodes: In Ascaris megalocephala (also called Parascaris univalens ) the single pair of chromosomes in diploid germ-line cells is broken into more than 40 fragments in the progenitors of the somatic cells at a fixed stage of early embryonic development (for review, see Muller et al. 1991). These fragments must be stabilized, because they are transmitted intact throughout subsequent somatic cell divisions. Although most organisms do not undergo such extensive chromosome breakage, many exhibit a developmentally regulated response to an accidentally broken chromosome end. In the 1930s, Barbara McClintock showed that in a growing maize plant, when a ring dicentric chromosome was ruptured as its two centromeres separated, the resulting broken ends fused with each other to form a new ring chromosome. Importantly, McClintock made the original observation that this fate of a broken end was not inevitable: Depending on the tissue type and developmental stage, the broken end could lose its tendency to fuse with other broken ends (McClintock 1939), and McClintock concluded that such a broken end had “healed.” The healed end thereby became as permanently stable as any normal telomere through all subsequent nuclear divisions. This implies that a permanent molecular modification of the broken end of the chromosome occurred upon healing. Such healing specifically...

Fish analysis of supernumerary ring chromosome in dermatofibrosarcoma protuberans.

Abstract: We describe the light- and electron microscopic, immunohistochemical, cell culture characteristics and cytogenetic findings of a case of dermatofibrosarcoma protuberans (DFSP). Cytogenetically, the lesion exhibited trisomy 8 and a supernumerary ring chromosome as the only clonal abnormalities found in about 35% of the cells analyzed. FISH-analysis of metaphase chromosomes revealed that the ring chromosome contained chromosome 17 sequences. Hybridization with a chromosome 17 centromere specific probe gave three signals in about 19% of the interphase nuclei suggesting that the ring also had a centromere derived from chromosome 17. These observations add to the evidence that supernumerary ring chromosomes, preferentially derived from chromosome 17, and trisomy 8 are non-random abnormalities in DFSP. Our findings also demonstrate the usefulness of FISH for identifying the origin of marker ring chromosomes.

Chromosome 18 replaced by two ring chromosomes of chromosome 18 origin.

Abstract: We here describe the first example of the replacement of an autosome by two ring chromosomes originating from the missing chromosome, presented in a patient with a single chromosome 18 and two additional ring chromosomes. Detailed fluorescence in situ hybridization (FISH) analysis revealed the chromosome 18 origin of both ring chromosomes and characterized the small and the large ring chromosome as derivatives of the short and long arm of chromosome 18, respectively. The loss of subtelomeric regions of the short and the long arm of chromosome 18 in the ring chromosomes was confirmed by FISH studies. Molecular studies showed the exclusive presence of the paternal alleles for microsatellite markers located distal to the short and long arm loci D18S843 and D18S474, respectively. This indicates the maternal origin of both rings and provides evidence for substantial deletions of the distal parts of both arms of chromosome 18 in the ring chromosomes. The dysmorphic features of the patient can be explained by these deletions in both chromosome arms, as the clinical findings partly overlap with observations in 18p- and 18q-syndrome and are similar to some cases of ring chromosome 18. Centromere misdivision is suggested as one mechanism involved in the formation of the ring chromosomes.

[Turner's syndrome--correlation between karyotype and phenotype].

Abstract: Turner's syndrome is defined as a congenital disease determining by quantitative and/or structural aberrations of one from two X chromosomes with frequent presence of mosaicism. Clinically it is characterized by growth and body proportion abnormalities, gonadal dysgenesis resulting in sexual infantilism, primary amenorrhoea, infertility, characteristic stigmata, anomalies of heart, renal and bones and the presence of some diseases like Hashimoto thyroiditis with hypothyroidism, diabetes mellitus type 2, osteoporosis, hypertension. Turner's syndrome occurs in 1:2000 to 1:2500 female livebirth. The most frequent X chromosome aberrations in patients with phenotype of Turner syndrome are as follows: X monosomy - 45,X; mosaicism (50-75%), including 45,X/46,XX (10-15%), 45,X/46,XY (2-6%), 45,X/46,X,i(Xq), 45,X/46,X,del(Xp), 45,X/46,XX/47,XXX; aberration of X structure: total or partial deletion of short arm of X chromosome (46,X,del(Xp)) isochromosom of long arm of X chromosome (46,X,(i(Xq)), ring chromosome (46, X,r(X)), marker chromosome (46,X+m). Searching of X chromosome and mapping and sequencing of genes located at this chromosome (such as SHOX, ODG2, VSPA, SOX 3) have made possible to look for linkage between phenotypes and adequate genes or regions of X chromosome. In this paper current data concerning correlation between phenotype and karyotype in patients with TS have been presented.