Transsexualität und H-Y Antigen
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See also: Zur Frage der Bedeutung des H-Y-Antigens für die Gonadendetermination und für die Differenzierung der GeschlechtsidentitätGeburtshilfe Frauenheilkd 1981; 41(01): 58-60DOI: 10.1055/s-2008-1036843Keywords:
Virilization
All human X-linked genes known so far, except for the Xp/Yp pseudoautosomal genes, are conserved as a single linkage group on the murine X chromosome. We show that the interleukin-9 (IL-9) receptor gene ( IL9R ), which is located within the human Xq/Yq homology region, maps to the murine chromosome 11. The Xq/Yq pseudoautosomal region (Xq PAR) thus represents a second region on the human X chromosome which is not X linked in mice. Furthermore, we show that IL9R is absent on the Y of great apes. IL9R is thus exceptional among X/Y genes in that it is X linked in some mammals, but autosomal or pseudoautosomal in others. Genes located on the X and the Y generally escape X inactivation. An exception to this rule is SYBL1 , a gene located in Xq PAR. SYBL1 is X inactivated and is inactive on the Y chromosome. In contrast, we show that IL9R expression does occur from the Y, the active and the inactive X chromosomes. This finding raises the question of how the transcriptional regulation of genes within Xq PAR occurs and how the X inactivation status of IL9R has evolved following the autosome to X and the X to X/Y translocation. The evolutionary analysis of the IL9R gene, which is located at 10 kb from the telomere, and its pseudogenes at several telomeres, also provides insight into the evolution of these loci and of subtelomeric regions in general.
Pseudoautosomal region
Pseudogene
Dosage compensation
Skewed X-inactivation
Homology
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Mammals have XX female :XY male chromosomal sex determination in which a small heterochromatic Y controls male development. Only a few active genes have been identified on the Y, including the testis determining factor SRY and candidate spermatogenesis genes. These genes, as well as several pseudogenes, have close relatives on the X, confirming that the Y was originally homologous to the X, but has been progressively degraded. We used comparative gene mapping of sex chromosomes from the three major groups of extant mammals (eutherians, marsupials and monotremes) to deduce how the X and Y evolved from a pair of autosomes, and how SRY assumed control of sex determination. We found that part of the X, and a corresponding region of the Y chromosome, is shared by all mammals and must be very ancient, but part of the X (and Y) was added quite recently. I propose that a small original X and Y were enlarged by cycles of autosomal addition to one partner, recombination onto the other and continuing attrition of the compound Y. This addition-attrition hypothesis predicts that the pseudoautosomal region of the human X is merely a relic of the last addition, and that the gene content of the pseudoautosomal region may well differ in different mammalian lineages. The only genes which remained active on the conserved or added regions of the Y were those, like SRY , that evolved functions in male sex determination and differentiation distinct from the general functions of their X-linked partners. Although the vertebrate gonadogenesis pathway is highly conserved, its control circuitry has probably changed radically and rapidly in evolution.
Pseudoautosomal region
Testis determining factor
Pseudogene
Dosage compensation
W chromosome
Heterogametic sex
Evolution of mammals
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This chapter contains sections titled: Cytogenetic Analysis of Bovine Sex Chromosomes X and Y Chromosome Genetic and Physical Maps The Pseudoautosomal Region Pseudoautosomal Boundary The MSY Region Bovine Y-Chromosome Phylogeny Sex Chromosome Abnormalities Sex Chromosomes QTLs References
Pseudoautosomal region
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Human Y(+) XX maleness has been shown to result from an abnormal terminal Xp-Yp interchange that can occur during paternal meiosis. To test whether human XY females are produced by the same mechanism, we followed the inheritance of paternal pseudoautosomal loci and Xp22.3-specific loci in two XY female patients. Y-specific sequences and the whole pseudoautosomal region of the Y chromosome of their fathers were absent in these patients. However, the entire pseudoautosomal region and the X-specific part of Xp22.3 distal to the STS locus had been inherited from the X chromosome of the respective father. This Xp transfer to Yp was established by in situ hybridization experiments showing an Xp22.3-specific locus on Yp in both cases. Such results demonstrate that an abnormal and terminal X-Y interchange generated the rearranged Y chromosome of these two XY females; they appear to be the true countertype of Y(+) XX males. In these patients, who also display some Turner stigmata, the Y gene(s) involved in this phenotype is (are) localized to interval 1 or 2. If the loss of such gene(s) affects fetal viability, their proximity to TDF would account for the underrepresentation of interchange 46,XY females compared with Y(+) XX males.
Pseudoautosomal region
X-linked recessive inheritance
Dosage compensation
Skewed X-inactivation
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The human testis-determining gene was recently isolated from a 35 kb region on the human Y chromosome which was present in four sex-reversed individuals, three XX males and one true hermaphrodite. One of the XX males and the true hermaphrodite were sibs. A more detailed molecular analysis of these two patients and their family for Y-DNA sequences including the testis-determining gene, SRY was performed. The father was found to harbor two copies of SRY, one on his Y chromosome and the other on his X chromosome located at Xp22 determined by in situ hybridization. Somatic cell hybrids were generated from peripheral blood lymphocytes. Analysis of Y chromosome-negative somatic cell hybrids from the XX male, the true hermaphrodite and their father, revealed that both the X and Y pseudo-autosomal boundaries were present. The present of both boundaries suggests than an unequal interchange of X and Y material occurred with the cross-over breakpoint located within the X pseudo-autosomal region. The paternal SRY-bearing X chromosome was transmitted to two of his children, a 46 XX true hermaphrodite and a 46,XX male. The presence of SRY on an X chromosome associated with two sex phenotypes strongly suggests that the phenotypic variability was caused by differential inactivation of the SRY-bearing X chromosome, thereby influencing SRY expression.
Testis determining factor
Hermaphrodite
Sex reversal
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Cytogenetic analysis of patients with Ullrich-Turner syndrome (UTS) may fail to detect low levels of Y chromosome mosaicism or Y-derived marker chromosomes. More sensitive polymerase chain reaction (PCR)-based tests have been developed; however, applicability of these data to prognosis of virilization and gonadoblastoma development has not been investigated adequately. We used a multiplex PCR-based method to detect two Y-specific sequences, SRY and AMGLY. Thirteen patients with UTS without cytogenetically detected Y chromosomes were studied. Y-specific sequences were detected in 5 patients by multiplex PCR. A cryptic translocation involving the Y chromosome was found in one patient with severe virilization of external genitalia and a male phenotype. Y chromosomal mosaicism was detected in peripheral blood and in both gonads of one patient, and only in the left gonad of another patient. Existence of a Y-derived marker was demonstrated in 2 patients, one of whom had no testicular tissue or virilization. Consistent with previous reports, we conclude that PCR is more sensitive than classical cytogenetic analysis and detects patients with Y-specific sequences in blood cells. However, the absence of Y-specific material in blood is not a sufficient reason to reject surgical treatment in case of virilization. Am. J. Med. Genet. 76:283–287, 1998. © 1998 Wiley-Liss, Inc.
Virilization
Gonadoblastoma
Testis determining factor
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Cytogenetic analysis of patients with Ullrich-Turner syndrome (UTS) may fail to detect low levels of Y chromosome mosaicism or Y-derived marker chromosomes. More sensitive polymerase chain reaction (PCR)-based tests have been developed; however, applicability of these data to prognosis of virilization and gonadoblastoma development has not been investigated adequately. We used a multiplex PCR-based method to detect two Y-specific sequences, SRY and AMGLY. Thirteen patients with UTS without cytogenetically detected Y chromosomes were studied. Y-specific sequences were detected in 5 patients by multiplex PCR. A cryptic translocation involving the Y chromosome was found in one patient with severe virilization of external genitalia and a male phenotype. Y chromosomal mosaicism was detected in peripheral blood and in both gonads of one patient, and only in the left gonad of another patient. Existence of a Y-derived marker was demonstrated in 2 patients, one of whom had no testicular tissue or virilization. Consistent with previous reports, we conclude that PCR is more sensitive than classical cytogenetic analysis and detects patients with Y-specific sequences in blood cells. However, the absence of Y-specific material in blood is not a sufficient reason to reject surgical treatment in case of virilization. Am. J. Med. Genet. 76:283–287, 1998. © 1998 Wiley-Liss, Inc.
Virilization
Gonadoblastoma
Testis determining factor
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