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Sex Chromosome Pairing and Fertility in the Heterogametic Sex of Mammals and Birds
Published in Christopher B. Gillies, Fertility and Chromosome Pairing: Recent Studies in Plants and Animals, 2020
Recently, some important advances have been made on the behavior of the human XY pair by the use of DNA probes, which had been foreseen in speculative papers. Polani95 and Burgoyne96 raised the assumption of regular crossing over in the pairing segment of the human XY pair. Polani95 argued that the short arm of the Y chromosome may share homologous genes with the distal region of the short arm of the X chromosome. Furthermore, he assumed that, besides “regular” crossing over, recombination could occur (at lower frequencies) beyond the homologous region.95 In such low frequency, non symmetrical recombination, the testis-determining factor (TDF gene) could be occasionally transferred to the X chromosome. Gametes carrying this TDF-bearing, X chromosome could give rise to XX males, as previously proposed by Ferguson-Smith.97 Burgoyne96 assumed that recombination in the human XY pair could be “obligatory” for a short, distal segment. Thus, genes situated beyond the location of the obligatory recombination would show no sex linkage, having a “pseudoautosomal” inheritance pattern. Most of these predictions have now been proved.
Sexual Differentiation: Immunological Aspects
Published in Gérard Chaouat, The Immunology of the Fetus, 2020
Joyce A. Shelton, Erwin Goldberg
The most recent studies designed to shed light on the role of Hy and/or Tdy involve Sxr, “sex-reversed” mice (summarized in Table 1). Originally described by Cattanach and co-workers,42 these mice carry a trait which causes XX individuals to develop as phenotypic, but sterile, males. In X/YSxr carrier males, an extra copy of the segment of the Y chromosome which carries Tdy has been transposed to the long arm of the Y.43 This segment is, therefore, attached to the portion of the Y chromosome that forms an obligatory cross-over with the X chromosome during meiosis. Thus Sxr is transferred to the long arm of one of the two X chromosomes, which results in half of the XX progeny receiving the XSxr and developing into males. Sex-reversed XX males invariably type H-Y positive by both serological44 and transplantation45 methodologies.
Genetic Causes of Male Infertility
Published in Botros Rizk, Ashok Agarwal, Edmund S. Sabanegh, Male Infertility in Reproductive Medicine, 2019
Amr Abdel Raheem, Mohamed Wael Ragab, Tarek M. A. Aly
46,XX male syndrome (de la Chapelle syndrome) is a rare syndrome that occurs in 1/10,000–20,000 of newborn males [7]. In the majority of cases, this syndrome is caused by the translocation of the sex-determining region of the Y chromosome (SRY region, which plays a crucial role in differentiation of bipotential gonads into testes) to the X chromosome or an autosome. A minority of cases are SRY negative, which presumably had another cause of activation of the testicular differentiation cascade. Clinically, 46XX men resemble KF men and present with small firm testes, hypogonadism, and azoospermia. However, unlike KF, the azoospermia in 46XX men is due to complete absence of genes located in AZF regions. Accordingly, these patients have no chance of successful testicular sperm retrieval [4].
Systematic review of hormone replacement therapy in the infertile man
Published in Arab Journal of Urology, 2018
Amr El Meliegy, Ahmad Motawi, Mohamed Ahmed Abd El Salam
The term primary hypergonadotrophic hypogonadism refers to testicular disorders and is characterised by low serum testosterone despite high levels of FSH and LH. Low testosterone production results in impaired spermatogenesis (primary testicular failure) as seen in congenital anorchia, undescended testis, Sertoli cell only syndrome (germ cell aplasia), or after testicular injury from trauma, infection, surgery, exposure to chemo/radiotherapy or drug induced (e.g. ketoconazole, flutamide, spironolactone, etc.). In addition, genetic causes for primary testicular failure are described such as numerical chromosome aberrations including: Klinefelter syndrome, XX-male syndrome, XYY syndrome and Y chromosome microdeletions [16].
Contemporary genetics-based diagnostics of male infertility
Published in Expert Review of Molecular Diagnostics, 2019
Alberto Ferlin, Savina Dipresa, Andrea Delbarba, Filippo Maffezzoni, Teresa Porcelli, Carlo Cappelli, Carlo Foresta
Aneuploidies are defined by an abnormal number of chromosomes with respect to the euploid state (46,XY or 46,XX). The most frequent aneuploidies detected in infertile men involve the sex chromosomes, examples include the Klinefelter syndrome (at least one extra X chromosome), mixed gonadal dysgenesis (45,X/46,XY), and the 46,XX male syndrome.