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.

Condensation anomalies and exclusion in micronuclei of rearranged chromosomes in human fibroblasts cultured in vitro

Abstract: Anomalies of chromatin condensation, such as fragmentation, uncoiling and pulverization, were observed in XP9UV25, a xeroderma pigmentosum fibroblast clone in which a high proportion of cells carried an end-to-end dicentric chromosome, dic (5;16) (p15.2;q24), that gives rise during propagation in culture to a variety of dicentric and monocentric derivatives. The coiling anomaly affected exclusively part of a rearranged chromosome, in particular the region previously involved in breakage events. The heterochromatic 16q region, which is a preferential breakpoint in the formation of dicentric and monocentric derivatives, was consistently the limit of the uncoiled or pulverized regions. This observation suggests that the anomalous chromatin behavior could derive from alteration of a region relevant for the correct condensation of the chromosome. In XP9UV25 the frequency of nuclei with associated micronuclei increased with time in culture, in parallel with that of mitoses with dicentric chromosomes. In situ hybridization with DNA probes specific for chromosomes 5 and 16 revealed hybridization signals in about 40% of micronuclei. Since the frequency of micronuclei is about ten times less than that of dicentrics, it is probable that only the rearranged chromosomes undergoing coiling anomalies are excluded in micronuclei.

Ring chromosome 4 in a patient with early onset type 2 diabetes, deafness, and developmental delay

Abstract: To date, most ring formations of chromosome 4 lose distal 4p and usually include the Wolf-Hirschhorn syndrome region [WHS]. We describe a case with r(4) in a girl who presented without features of WHS; she had mild developmental delay, deafness, short stature, obesity, and the onset of type 2 diabetes in adolescence, a distinctive phenotype. Although 4p was significantly deleted on Giemsa banding, the 4p junction was distal to the WHS and FGFR3 but proximal to the D4S3360 marker. The 4q breakpoint was close to the telomere. The phenotype appears different from previous patients with 4p- or r(4), which have had more extensive 4p deletion.

Familial supernumerary marker chromosome evolution through three generations

Abstract: A mosaic chromosome complement, 46,XY/47,XY,+r(15), was detected at prenatal diagnosis Family studies showed the mother and one of her two children to have a bisatellited supernumerary marker chromosome (SMC) in all lymphocytes examined The maternal grandfather also showed a bisatellited SMC, but in only 2 per cent of his lymphocytes NOR, DA/DAPI, and chromosome 15 centromere and short arm-specific probes confirmed the identify of the bisatellited SMC and of ring SMC as derived from chromosome 15 An apparently normal male was born at full term At age 1 year, the baby continues to have normal growth and development The bisatellited 15 likely originated by somatic mutation in the grandfather (2 per cent cells), was transmitted unchanged to the daughter and grandson (germline transmission, no mosaicism), and then evolved by excising the satellites and forming a ring SMC in the index case Progressive changes in the frequency and subsequent changes in the structure of this SMC illustrate the unusual characteristics of chromosome 15

Ring chromosome 4 mosaicism and Potter sequence.

Abstract: A 46,XY/46,XY,r(4) mosaicism is described in a malformed male newborn with bilateral renal agenesis. A review of the phenotypic findings in the previously reported ring chromosome 4 patients is made and the importance of the detection of chromosomal abnormalities towards the nosology of malformation sequences is discussed.