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.

Ring chromosome 7 and sacral agenesis

Abstract: A ring chromosome 7 was found in a 19-month-old girl with microcephaly, growth and developmental delay, multiple angiomas, and partial sacral agenesis. Absent sacrum is a frequent finding in patients with 7q terminal deletions; in fact, genes involved in the sacral agenesis are localized in 7q36. However, this anomaly was not described previously in patients with a ring chromosome 7. High resolution G-banding chromosome and fluorescence in situ hybridization (FISH) demonstrated that our patient lost this region during ring formation.

Evolutionary and clinical neocentromeres: two faces of the same coin?

Abstract: It has been hypothesized that human clinical neocentromeres and evolutionary novel centromeres (ENC) represent two faces of the same phenomenon. However, there are only two reports of loci harboring both a novel centromere and a clinical neocentromere. We suggest that only the tip of the iceberg has been scratched because most neocentromerization events have a very low chance of being observed. In support of this view, we report here on a neocentromere at 9q33.1 that emerged in a ring chromosome of about 12 Mb. The ring was produced by a balanced rearrangement that was fortuitously discovered because of its malsegregation in the propositus. Chromatin-immunoprecipitation-on-chip experiments using anti-centromere protein (CENP)-A and anti-CENP-C antibodies strongly indicated that a novel centromeric domain was present in the ring, in a chromosomal domain where an ENC emerged in the ancestor to Old World monkeys.

A clinical, cytogenetic and molecular study of 47 females with r(X) chromosomes.

Abstract: We studied 47 patients with a 45,X/46,X,r(X) karyotype to identify phenotypic differences between these patients and 45,X patients, and to determine whether these differences could be explained by the status of genes within the ring. Only 2 patients had the 'severe' r(X) phenotype, and both were consistent with this resulting from functional disomy of genes normally subject to X inactivation. A further 7 patients also carried active rings but these patients did not have a more severe phenotype than those whose rings were inactivated, probably because their rings were smaller and did not contain the (as yet unidentified) genes whose functional disomy is particularly damaging. Patients with a r(X) did not show clear physical differences when compared with a 45,X series, except for a possible reduction in the frequency of oedema in those whose r(X) had an Xq breakpoint distal to DXS128E, at Xq13.2. Thus some protection from oedema may be provided by the presence of two copies of Xq13.2.

An unstable ring chromosome in a female infant with hypotonia, seizures, and retarded development.

Abstract: The occurrence of a ring autosome in human cells has been described in association with congenital abnormalities and mental retardation (Turner, Jennings, Den Dulk, and Stapleton, I962; Wang, Melnyk, McDonald, Uchida, Carr, and Goldberg, I962; Genest, Leclerc, and Auger, I963; Lucas, Kemp, Ellis, and Marshall, I963; Bain and Gauld, I963; de Grouchy, Leveque, Debauchez, Salmon, Lamy, and Marie, I964; Gropp, Jussen, and Ofteringer, I964; Gordon and Cooke, I964). A ring X chromosome has been reported in a few cases of ovarian agenesis (Lindsten, I963; Luers, Nevinny-Stickel, and Struck, I964), and ring chromosomes have been noted in neoplasms (Levan, I956) and in irradiated cells (Bender and Gooch, I962). The present report describes an infant who was found to have mosaicism in cultured blood and skin cells. One cell line was normal and another line contained a ring chromosome in addition to the normal complement.