title: The program of sex chromosome pairing in meiosis is highly conserved across marsupial species: implications for sex chromosome evolution.
abstract: Marsupials present a series of genetic and chromosomal features that are highly conserved in very distant species. One of these features is the absence of a homologous region between X and Y chromosomes. According to this genetic differentiation, sex chromosomes do not synapse during the first meiotic prophase in males, and a special structure, the dense plate, maintains sex chromosome association. In this report we present results on the process of meiotic sex chromosome pairing obtained from three different species, Thylamys elegans, Dromiciops gliroides, and Rhyncholestes raphanurus, representing the three orders of American marsupials. We have investigated the relationships between the axial structures organized along sex chromosomes and the formation of the dense plate. We found that in the three species the dense plate arises as a modification of sex chromosomal axial elements, but without the involvement of other meiotic axial structures, such as the cohesin axes. Considering the phylogenetic relationships among the marsupials studied here, our data reinforce the idea that the dense plate emerged early in marsupial evolution as an efficient mechanism to ensure the association of the nonhomologous sex chromosomes. This situation could have influenced the further evolution of sex chromosomes in marsupials.
authors.affiliation: Programa de Genética Humana, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago 7.
authors.forename: Jesús
authors.initials: J
authors.lastname: Page
authors.forename: Soledad
authors.initials: S
authors.lastname: Berríos
authors.forename: María Teresa
authors.initials: MT
authors.lastname: Parra
authors.forename: Alberto
authors.initials: A
authors.lastname: Viera
authors.forename: José Angel
authors.initials: JA
authors.lastname: Suja
authors.forename: Ignacio
authors.initials: I
authors.lastname: Prieto
authors.forename: José Luis
authors.initials: JL
authors.lastname: Barbero
authors.forename: Julio S
authors.initials: JS
authors.lastname: Rufas
authors.forename: Raúl
authors.initials: R
authors.lastname: Fernández-Donoso
mesh_terms: D000818:Animals; D002503:Centromere / Q000648:ultrastructure; D023902:Chromosome Pairing; D048293:Didelphis / Q000235:genetics; D019143:Evolution, Molecular; D008297:Male; D008394:Marsupialia; D008540:Meiosis; D008856:Microscopy, Fluorescence; D008938:Mitosis; D009893:Opossums / Q000235:genetics; D010766:Phosphorylation; D010802:Phylogeny; D011418:Prophase; D012730:Sex Chromosomes; D013045:Species Specificity; D014960:X Chromosome; D014998:Y Chromosome