Cytogenetic and Molecular studies of Ring (X) Chromosomes
Cytogenetic and Molecular studies of Ring (X) Chromosomes
Until now, no large scale investigation of patients with a ring (X) chromosome had been carried out, so this study of 47 females mosaic for a ring (X) was set up in order to identify whether; i) a ring (X) chromosome cell line may protein against certain somatic features of Turner syndrome, and if so where candidate gene/s may be located, and ii) confirm the hypothesis that the absence or incomplete expression of XIST is related to a more severe phenotype, and whether the severity is influenced by the genetic content of the ring and/or its frequency. Cytogenetic and molecular studies of each patient established; i) whether XIST gene was included in the ring and being expressed, ii) its genetic content, iii) the frequency of the 46,X,r(X) cell line, and iv) the parental origin of the normal X and ring (X). A detailed clinical phenotype was available on 33 cases.
Twenty-five patients have inactive rings and a phenotype consistent with Turner syndrome. The absence of certain somatic Turner features, such as neck webbing and a wide carrying angle, in these ring (X) patients suggests that a ring (X) chromosome can protect against particular Turner features. Genetic mapping of these rings suggests that the gene/s responsible might be located between Xp11.2 and Xp22.1. When XIST is absent, or not expressed, a severe phenotype is seen in 2 patients and an unexpectedly mild phenotype in 6 patients. The inability of the ring to inactivate resulting in functional disomy of the sequence contained within it would explain the severe phenotype seen in 2 cases. There are 3 possible explanations for the unexpectedly mild phenotypes; i) the absence of gene/s from the ring, which when functionally disomic, are responsible for the severe phenotype, ii) ring formation and the loss of the XIST gene happened after the establishment of the inactive X status, or iii) tissue-limited distribution of cells containing the ring (X).
University of Southampton
1999
Turner, Caroline
(1999)
Cytogenetic and Molecular studies of Ring (X) Chromosomes.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Until now, no large scale investigation of patients with a ring (X) chromosome had been carried out, so this study of 47 females mosaic for a ring (X) was set up in order to identify whether; i) a ring (X) chromosome cell line may protein against certain somatic features of Turner syndrome, and if so where candidate gene/s may be located, and ii) confirm the hypothesis that the absence or incomplete expression of XIST is related to a more severe phenotype, and whether the severity is influenced by the genetic content of the ring and/or its frequency. Cytogenetic and molecular studies of each patient established; i) whether XIST gene was included in the ring and being expressed, ii) its genetic content, iii) the frequency of the 46,X,r(X) cell line, and iv) the parental origin of the normal X and ring (X). A detailed clinical phenotype was available on 33 cases.
Twenty-five patients have inactive rings and a phenotype consistent with Turner syndrome. The absence of certain somatic Turner features, such as neck webbing and a wide carrying angle, in these ring (X) patients suggests that a ring (X) chromosome can protect against particular Turner features. Genetic mapping of these rings suggests that the gene/s responsible might be located between Xp11.2 and Xp22.1. When XIST is absent, or not expressed, a severe phenotype is seen in 2 patients and an unexpectedly mild phenotype in 6 patients. The inability of the ring to inactivate resulting in functional disomy of the sequence contained within it would explain the severe phenotype seen in 2 cases. There are 3 possible explanations for the unexpectedly mild phenotypes; i) the absence of gene/s from the ring, which when functionally disomic, are responsible for the severe phenotype, ii) ring formation and the loss of the XIST gene happened after the establishment of the inactive X status, or iii) tissue-limited distribution of cells containing the ring (X).
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Published date: 1999
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Local EPrints ID: 463738
URI: http://eprints.soton.ac.uk/id/eprint/463738
PURE UUID: c8fa9098-0931-408a-99cc-74e3d3edba2e
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Date deposited: 04 Jul 2022 20:56
Last modified: 04 Jul 2022 20:56
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Author:
Caroline Turner
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