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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.


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Journal ArticleDOI
TL;DR: This is the first cytogenetic description, with banding techniques, of a malignant meningioma, from a patient submitted to two surgeries separated by 1 year, and it is reported that there was a recurrent trisomy of chromosome 3.

38 citations

Journal ArticleDOI
TL;DR: Results indicate that the gene coding for the liver-type subunit PFKL, a key regulatory enzyme of glycolysis, is located on chromosome 21q22.3.
Abstract: The three structural loci encoding human phosphofructokinase, a key regulatory enzyme of glycolysis, are located on separate chromosomes. The gene coding for the liver-type subunit PFKL has previously been assigned to chromosome 21. We have used a subunit- and human-specific monoclonal antibody to liver PFK to detect the expression of human PFKL in hamster x human hybrid cell lines. A cell line carrying an 8;21 translocation which contains all of chromosome 21 except the band 21q22.3 was negative for the expression of PFKL whereas cell lines carrying the reciprocal 8;21 translocation were positive. In addition, a cell line with a ring chromosome 21 containing a breakpoint which excluded the distal part of the q22.3 band was negative for expression of PFKL. These results indicate that human PFKL is located on chromosome 21q22.3.

38 citations

Journal ArticleDOI
TL;DR: A 46,X,r(X) karyotype was found in a three and a half year old girl with short stature, facial dysmorphism and developmental delay, consistent with the phenotype described in a limited number of patients with small ring X chromosomes lacking the XIST locus.
Abstract: A 46,X,r(X) karyotype was found in a three and a half year old girl with short stature, facial dysmorphism and developmental delay. The clinical findings were consistent with the phenotype described in a limited number of patients with small ring X chromosomes lacking the XIST locus, a critical player in the process of X chromosome inactivation. Surprisingly, in our patient, fluorescent in situ hybridisation demonstrated that the XIST locus was present on the ring X. However, expression studies showed that there was no XIST transcript in peripheral blood cells, suggesting that the ring X had not been inactivated. This was confirmed by the demonstration that both of the patient's alleles for the androgen receptor gene were unmethylated, and that both of the patient's ZXDA alleles were expressed. The active nature of the ring X would presumably result in overexpression of genes that may account for the developmental delay observed for the patient. Using polymorphic markers along the X chromosome, the ring X was determined to be of paternal origin with one breakpoint in the long arm between DXS8037 and XIST and one in the short arm in Xp11.2 between DXS1126 and DXS991. To attempt to determine why the XIST gene failed to be expressed, the promoter region was sequenced and found to have a base change at the same location as a variant previously associated with nonrandom X chromosome inactivation. This mutation was not seen in over one hundred normal X chromosomes examined; however, it was observed in the paternal grandmother who did not show substantial skewing of X chromosome inactivation.

38 citations

Journal ArticleDOI
TL;DR: It is proposed that mosaicism resulting in the absence of the ring from tissues, such as the brain, which are important in the severe phenotype, and the presence of an inactive X in some tissues at some time, exemplified by the demonstration of XIST expression in one patient.
Abstract: Small ring (X) chromosomes lacking the XIST gene at Xq132 have been associated with a severe phenotype that includes mental retardation, facial dysmorphism and congenital abnormalities It has been hypothesised that the loss of XIST results in functional disomy for the sequences contained in the ring We studied 47 females with a 45,X/46,r(X) karyotype and found seven to have an XIST-negative ring Only one of the seven patients had the severe phenotype The remaining six patients had physical phenotypes consistent with Turner syndrome The rings were characterised cytogenetically and molecularly The severe phenotype in one patient can be explained by the absence of XIST expression, the relatively large amount of Xp material in the ring and, possibly, the concomitant maternal uniparental isodisomy We propose three explanations for the unexpectedly mild phenotypes in the remaining six patients; (1) the rings contained limited amounts of X-chromosome material, and sequences that, when functionally disomic, result in a severe phenotype were absent; (2) mosaicism resulting in the absence of the ring from tissues, such as the brain, which are important in the severe phenotype and (3) the presence of an inactive X in some tissues at some time, exemplified by the demonstration of XIST expression in one patient

38 citations

Journal ArticleDOI
TL;DR: Biotinylated centromere and telomere probes were used for in situ hybridization to show the presence of centromeric and telomeric sequences in the Y-marker chromosome, suggesting that the deletion of this marker chromosome is interstitial.
Abstract: A 17-year-old girl (S.M.) and a 13-year-old girl (C.L.) both with Ullrich-Turner syndrome (UTS) were found to have 45,X/46,X, +mar mosaicism. The marker chromosomes in both patients were very small in size. In S.M. the marker chromosome was present in 80% of phytohemaglutinin-stimulated lymphocytes, 28% of skin fibroblasts, and 11–20% of gonadal fibroblasts. In C.L., the small marker chromosome was found in 50% of stimulated lymphocytes. S.M. is of normal height, but C.L. is short. Molecular hybridization with a number of Y-specific DNA probes demonstrated their presence in S.M. but absence in C.L. In situ hybridization with Y-specific and X-centromere-specific DNA probes confirmed the Y origin of the marker chromosome in S.M. and the X origin of the minute chromosome in C.L. Biotinylated centromere and telomere probes were also used for in situ hybridization to show the presence of centromeric and telomeric sequences in the Y-marker chromosome, suggesting that the deletion of this marker chromosome is interstitial.

37 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202310
202221
202123
202019
201919
201836