Turner syndrome: a cytogenetic and molecular study

Jacobs, Patricia A.; Dalton, Pamela; James, Rowena S.; Mosse, K. A.; Power, Monica M.; Robinson, David; Skuse, David

doi:10.1046/j.1469-1809.1997.6160471.x

Cited by 141 publications

(133 citation statements)

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“…TS is cytogenetically characterized as 45, X. In 6-15 % of the cases, individuals with TS also have another cell line with 46 chromosomes due to presence of an extra ring chromosome X [11,40]. Ring chromosomes may be formed by either terminal breaks of two arms of the chromosome and their rejoining leading to loss of genetic material [38].…”

Section: Introductionmentioning

confidence: 99%

Molecular cytogenetic characterization of two Turner syndrome patients with mosaic ring X chromosome

Chauhan

Jaiswal

Lakhotia

et al. 2016

J Assist Reprod Genet

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Purpose In the present study, we reported two cases of TS with mosaic ring X chromosome showing common clinical characteristics of TS like growth retardation and ovarian dysfunction. The purpose of the present study was to cytogenetically characterize both cases. Methods Whole blood culture and G-banding were performed for karyotyping the cases following standard protocol. Origin of the ring chromosome and degree of mosaicism were further determined by fluorescence in situ hybridization (FISH). Breakpoints and loss of genetic material in formation of different ring X chromosomes r (X) in cases were determined with the help of cytogenetic microarray. Results Cases 1 and 2 with ring chromosome were cytogenetically characterized as 45, X [114]/46Xr (X) (p22.11q21.32) [116] and 45, X [170]/46, Xr (X) (p22.2q21.33) [92], respectively. Sizes of these ring X chromosomes were found to be~7 5 and~95 Mb in cases 1 and 2, respectively, using visual estimation as part of cytogenetic observation. In both cases, we observed breakpoints on Xq chromosome were within relatively narrow region between Xq21.33 and Xq22.1 compared to regions in previously reported cases associated with ovarian dysgenesis. Conclusions Our observation agrees with the fact that despite of large heterogeneity, severity of the cases with intact Xinactive specific transcript (XIST) is dependent on degree of mosaicism and extent of Xq deletion having crucial genes involved directly or indirectly in various physiological involving ovarian cyclicity.

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Section: Introductionmentioning

confidence: 99%

Molecular cytogenetic characterization of two Turner syndrome patients with mosaic ring X chromosome

Chauhan

Jaiswal

Lakhotia

et al. 2016

J Assist Reprod Genet

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“…Low-level X/XX seems to be mainly the result of premature centromere division, a phenomenon by which the two X chromosomal chromatids separate due to loss of centromere function (Fitzgerald 1983). However, as bi-parental inheritance of X chromosomes has been observed in ordinary-level X/XX that contains relatively large proportions of X monosomy clones (Robinson et al 1995;Jacobs et al 1997), the mosaic aneuploidy seems to result from the loss of an X chromosome from some cells during embryonic development. Nonetheless, the reasons for postzygotic X chromosome loss remain unclear.…”

Section: Introductionmentioning

confidence: 99%

X chromosome inactivation patterns in 45,X/46,XX mosaics

et al. 2001

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To investigate X chromosome inactivation (XCI) patterns in 45,X/46,XX mosaics, genomic DNA was extracted from peripheral blood samples of 15 female subjects who showed different proportions of 45,X cell clones. XCI patterns were analyzed using two assays. The first assay was the BstXI restriction endonuclease detection of an Xlinked phosphoglycerate kinase (PGK) gene polymorphism following digestion of the DNA with methylation-sensitive HpaII, or with methylation-insensitive AfaI as a control. The second assay was the detection of a CAG triplet repeat polymorphism in the X-linked androgen receptor (AR) gene after sodium bisulfite treatment. Of the 15 subjects, 11 were informative due to heterozygosity for at least one of the polymorphisms (6 were heterozygous for the PGK polymorphism and 9 were heterozygous for the AR polymorphism). Four of the 11 informative subjects (36%) showed extremely skewed XCI for at least one of the polymorphisms, which was a much higher incidence than previously reported for normal females. Moreover, 3 of these 4 women had proportions of 45,X cell clones greater than 20%. Although our results may be due to several possible cytogenetic or molecular mechanisms, the most likely explanation is that cases of 45,X/46,XX that contain relatively high levels of 45,X cell clones probably arose due to structural aberrations of the X chromosome undetectable by conventional karyotyping.

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“…An i(Xq), dicentric in the great majority of cases, is by far the most frequent structural anomaly associated with Turner syndrome, followed by X chromosome rings, Xp deletions and pseudodicentric chromosomes with breakpoints along Xp or Xq. 22 In the latter, as in the r(X), mosaicism for a 45,X cell line significantly contributes to Turner phenotypes. In the other rearrangements, Turner stigmata derive by monosomy for the X short arm 23 as in the case of our patients 1 and 2.…”

Section: Discussionmentioning

confidence: 99%

Opposite deletions/duplications of the X chromosome: two novel reciprocal rearrangements

et al. 2000

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Paralogous sequences on the same chromosome allow refolding of the chromosome into itself and homologous recombination. Recombinant chromosomes have microscopic or submicroscopic rearrangements according to the distance between repeats. Examples are the submicroscopic inversions of factor VIII, of the IDS gene and of the FLN1/emerin region, all resulting from misalignment of inverted repeats, and double recombination. Most of these inversions are of paternal origin possibly because the X chromosome at male meiosis is free to refold into itself for most of its length. We report on two de novo rearrangements of the X chromosome found in four hypogonadic females. Two of them had an X chromosome deleted for most of Xp and duplicated for a portion of Xq and two had the opposite rearrangement (class I and class II rearrangements, respectively). The breakpoints were defined at the level of contiguous YACs. The same Xp11.23 breakpoint was found in the four cases. That of the long arm coincided in three cases (Xq21.3) and was more proximal in case 4 (Xq21.1). Thus class I rearrangements (cases 1 and 2) are reciprocal to that of case 3, whilst that of case 4 shares only the Xp breakpoint. The abnormal X was paternal in the three cases investigated. Repeated inverted sequences located at the breakpoints of rearrangements are likely to favour the refolding of the paternal X chromosome and the recombination of the repeats. The repeat at the Xp11 may synapse with either that at Xq21.3 or that at Xq21.1. These rearrangements seem to originate as the Xq28 submicroscopic inversions but they are identifiable at the microscopic level and result from a single recombination event.

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Turner syndrome: a cytogenetic and molecular study

Cited by 141 publications

References 0 publications

Molecular cytogenetic characterization of two Turner syndrome patients with mosaic ring X chromosome

Molecular cytogenetic characterization of two Turner syndrome patients with mosaic ring X chromosome

X chromosome inactivation patterns in 45,X/46,XX mosaics

Opposite deletions/duplications of the X chromosome: two novel reciprocal rearrangements

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