Topic
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.
Papers published on a yearly basis
Papers
More filters
••
TL;DR: The fetal karyotype determined from cultured amniotic fluid cells revealed a ring chromosome 13 and, in addition to anencephaly, showed a wide variety of malformations.
Abstract: In the 33rd week of pregnancy an amniocentesis was performed because of low estriol. X-ray indicated the presence of anencephaly and a premature delivery was induced. Necropsy, in addition to anencephaly, showed a wide variety of malformations. The fetal karyotype determined from cultured amniotic fluid cells revealed a ring chromosome 13.
26 citations
••
TL;DR: It is suggested that the development of neurofibromatosis of unclear type in two r(22) carriers might be associated with somatic mutation of the NF2 locus due to instability of the ring chromosome(s), and in analogy, that somatic mutations of either NF1 or NF2 may account for some cases of neuroFibrom atosis which do not meet the criteria of both NF1 and NF2.
Abstract: Variable constitutional mosaicism, mos45,XY,-22/46,XY,-22,+mar/46,XY,-22,+r(22)/47,XY,-22,+r(22)+mar/ 47, XY,-22,+r(22)*2, was found in PHA-stimulated peripheral blood, in a lymphoblastoid cell line and in cultured skin fibroblasts from a mentally retarded patient with neurofibromatosis. Both the ring chromosome and the small extra marker chromosome stained positively by in situ hybridization with a chromosome 14/22-specific alphoid repeat probe. DNA dosage analysis showed constitutional loss of one copy of the arylsulfatase A gene (ARSA), consistent with its terminal location on 22q. There was no evidence of constitutional loss of D22S1 or D22S28 which flank the neurofibromatosis type 2 (NF2) locus. Analysis of two DNA samples from a skin neurofibroma indicated retainment of two copies of D22S1, whereas the results were ambiguous with respect to tumor-specific loss of one copy of D22S28. It is suggested that the development of neurofibromatosis of unclear type in two r(22) carriers might be associated with somatic mutation of the NF2 locus due to instability of the ring chromosome(s), and in analogy, that somatic mutation of either NF1 or NF2 may account for some cases of neurofibromatosis which do not meet the criteria of either NF1 or NF2. The occurrence of seminoma in the proband may be fortuitous, but could also be due to the presence of a seminoma-associated locus on chromosome 22.
26 citations
••
TL;DR: Three cases of ring chromosome 5 [r(5)], two familial (mother and daughter) and one sporadic are reported, with phenotype resembled that of the “ring syndrome” with prenatal onset of short stature, growth retardation, mild facial dysmorphism and normal psychomotor development.
Abstract: We report three cases of ring chromosome 5 [r(5)], two familial (mother and daughter) and one sporadic. The phenotype resembled that of the “ring syndrome” with prenatal onset of short stature, growth retardation, mild facial dysmorphism and normal psychomotor development. Extended metaphase and prometaphase chromosome preparations using G-, R- and Q-banding and scanning electron microscopy (SEM) failed to demonstrate deletion in the ring 5. Flow karyotype using the FACS cell sorter and peak area analysis showed the r(5) to be in the same position as the normal chromosome 5. The deletion that is presumably associated with ring formation appears to involve less that one megabase of DNA. In the “complex” rings, high resolution SEM showed fragile sites at the 5q34 and 5q35 region with frequent deletions at that site. A literature survey suggests that when a parent carries a ring chromosome about 80% of recognised pregnancies result in live birth. Of these, about half have a normal phenotype and karyotype, and half inherit the parental ring; about half of those acquiring the ring (20%) show significant mental retardation.
26 citations
•
TL;DR: A dysmorphic retarded fourteen-mont-old female with partial deletion of the long arm of chromosome 6 is presented, and the breakpoint in 6q was in region 2, probably at band 5.
Abstract: A dysmorphic retarded fourteen-mont-old female with partial deletion of the long arm of chromosome 6 is presented. The breakpoint in 6q was in region 2, probably at band 5. Eight other infants with a deletion involving the long arm of chromosome 6, including five with a ring chromosome 6, have been reported. The affected individuals have in common microcephaly, micrognathia, hypotonia and psychomotor retardation, but do not appear to have a distinctive phenotype.
26 citations
••
TL;DR: The patient illustrates the need to consider cytogenetic studies in patients with the Seckel phenotype, so that accurate diagnoses can be given to families, and suggests that there may be a locus for oligomeganephronia distal to the Wolf-Hirschhorn critical region on 4p.
Abstract: We present a patient with features suggestive of Seckel syndrome who was found to be mosaic for ring 4 chromosome. Seckel syndrome is a rare entity characterized by marked growth retardation, microcephaly, facies characterized by receding forehead and chin, large beaked nose, and severe retardation, usually thought to be inherited as an autosomal recessive condition. In addition, our patient had oligomeganephronia, a rare and usually sporadic renal malformation, previously reported in two other patients with abnormalities of chromosome 4. Besides pointing out the overlap between the Seckel phenotype and Wolf-Hirschhorn syndrome, our patient illustrates the need to consider cytogenetic studies in patients with the Seckel phenotype, so that accurate diagnoses can be given to families. Also, the case suggests that there may be a locus for oligomeganephronia distal to the Wolf-Hirschhorn critical region on 4p.
26 citations