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  • 1
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A series of fibroblasts from patients with numerical or structural aberrations of the X chromosome were scored for the amount of mRNA of ribosomal protein S4 (RPS4X). Haplo-insufficiency of this gene has been reported previously to be a possible cause of Turner syndrome. Our results show that the transcription rate of RPS4X correlates with the number of gene copies. This confirms earlier findings indicating that this gene escapes X inactivation. In addition, we demonstrate that this applies to structurally aberrant X chromosomes. Our results show that RPS4X does not give rise to a type of haplo-insufficiency in these cases, because it escapes inactivation, even on structurally aberrant X chromosomes from patients with Turner syndrome. We therefore assume that RPS4X is not the most prominent candidate gene for Turner syndrome.
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  • 2
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We report the mRNA and protein expression levels of human biglycan (BGN) in patients with different numbers of sex chromosomes. BGN maps to the distal long arm of the X chromosome, band Xq28, near the second pseudoautosomal region. BGN expression levels are reduced in 45,X Turner patients and increased in patients with additional sex chromosomes. This is suggestive of a pseudoautosomal gene or a gene that escapes X inactivation and that has an active Y chromosomal copy. However, we also provide evidence from hybrid cell lines that BGN is subject to X inactivation and that there is no homolog on the Y chromosome. This evidence excludes an escape from X inactivation. Moreover, additional Y chromosomes increase BGN expression levels, despite the absence of a Y chromosomal BGN gene. Therefore, another explanation has to be invoked. The “pseudoautosomal expression” of BGN may be attributed to a gene or genes that escape X inactivation and that regulate the transcriptional activity of BGN. This is the first report concerning an X chromosomal gene that does not show the conventional correlation between gene dosage and expression rate known from other X chromosomal genes.
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  • 3
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Ullrich-Turner syndrome (UTS) is frequently associated with monosomy X but may also occur with structural aberrations of the X and the Y chromosomes. It has been hypothesized that the ribosomal protein genes RPS4X and RPS4Y play a critical role in the prevention of UTS. Individual patients with a 46,X,i(Xq) karyotype cannot be differentiated phenotypically from 45,X UTS patients and carry three gene copies of RPS4X. Since haploinsufficiency of one or several gene(s) is thought to cause the UTS phenotype, direct assessment of RPS4X expression levels in these patients should establish whether RPS4X is involved in UTS. We have investigated fibroblasts of four 46,X,i(Xq) UTS patients with typical symptoms and a non-mosaic chromosome complement, and have found significantly increased RPS4X mRNA levels in all patients. Based on our results, we conclude that haploinsufficiency of RPS4X is not the cause of UTS.
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  • 4
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Duplications in Xp including the DSS (dosage sensitive sex reversal) region cause male to female sex reversal. We investigated two patients from families with Xp duplications. The first case was one of two sisters with karyotype 46,XY, der(22), t(X;22)(p11.3;p11)mat and unambiguous female genitalia. The living sister was developmentally retarded, and showed multiple dysmorphic features and an acrocallosal syndrome. The second case was a boy with a maternally inherited direct duplication of Xp21.3-pter with the breakpoint close to the DSS locus. He had multiple abnormalities and micropenis, but otherwise unambiguous male genitalia. We performed quantitative Southern blot analysis with probes from Xp22.13 to p21.2 to define the duplicated region. Clinical, cytogenetic, and molecular data from both patients were compared with those of previously reported related cases. A comparison of the extragenital symptoms revealed no differences between patients with or without sex reversal. In both cases, the symptoms were non-specific. Among 22 patients with a duplication in Xp, nine had unambiguous female genitalia and a well-documented duplication of the DSS region. Two patients with duplication of DSS showed ambiguous external genitalia. From these data, we conclude that induction of testicular tissue may start in these patients, but that the type of genitalia depends on the degree of subsequent degeneration by a gene in DSS.
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