title: Function of the sex chromosomes in mammalian fertility.
abstract: The sex chromosomes play a highly specialized role in germ cell development in mammals, being enriched in genes expressed in the testis and ovary. Sex chromosome abnormalities (e.g., Klinefelter [XXY] and Turner [XO] syndrome) constitute the largest class of chromosome abnormalities and the commonest genetic cause of infertility in humans. Understanding how sex-gene expression is regulated is therefore critical to our understanding of human reproduction. Here, we describe how the expression of sex-linked genes varies during germ cell development; in females, the inactive X chromosome is reactivated before meiosis, whereas in males the X and Y chromosomes are inactivated at this stage. We discuss the epigenetics of sex chromosome inactivation and how this process has influenced the gene content of the mammalian X and Y chromosomes. We also present working models for how perturbations in sex chromosome inactivation or reactivation result in subfertility in the major classes of sex chromosome abnormalities.
authors: Mammalian Developmental Epigenetics Group, Institut Curie, CNRS UMR3215 INSERM U934, 75248 Paris Cedex 05, France. edith.heard@curie.fr
authors: Edith
authors: E
authors: Heard
authors: James
authors: J
authors: Turner
mesh_terms: D000818:Animals; D002869:Chromosome Aberrations; D005260:Female; D005298:Fertility / Q000235:genetics*; D005718:Gametogenesis / Q000235:genetics; D005786:Gene Expression Regulation; D050172:Genes, X-Linked; D050173:Genes, Y-Linked; D006801:Humans; D007246:Infertility / Q000235:genetics; D008297:Male; D008322:Mammals / Q000235:genetics* / Q000502:physiology; D008540:Meiosis; D008957:Models, Genetic; D012730:Sex Chromosomes / Q000502:physiology*; D019849:Sex Determination Processes; D049951:X Chromosome Inactivation