Initiation of recombination suppression and PAR formation during the early stages of neo-sex chromosome differentiation in the Okinawa spiny rat, Tokudaia muenninki

作者：Chie Murata, Yoko Kuroki, Issei Imoto, Masaru Tsukahara, Naoto Ikejiri, Asato Kuroiwa · 发表于：BMC Evolutionary Biology · 年份：2015 · DOI：10.1186/s12862-015-0514-y · 被引用次数：15 · 研究领域：Genetic and Clinical Aspects of Sex Determination and Chromosomal Abnormalities、Developmental Biology and Gene Regulation、Chromosomal and Genetic Variations

BACKGROUND: Sex chromosomes of extant eutherian species are too ancient to reveal the process that initiated sex-chromosome differentiation. By contrast, the neo-sex chromosomes generated by sex-autosome fusions of recent origin in Tokudaia muenninki are expected to be evolutionarily 'young', and therefore provide a good model in which to elucidate the early phases of eutherian sex chromosome evolution. Here we describe the genomic evolution of T. muenninki in neo-sex chromosome differentiation. RESULTS: FISH mapping of a T. muenninki male, using 50 BAC clones as probes, revealed no chromosomal rearrangements between the neo-sex chromosomes. Substitution-direction analysis disclosed that sequence evolution toward GC-richness, which positively correlates with recombination activity, occurred in the peritelomeric regions, but not middle regions of the neo-sex chromosomes. In contrast, the sequence evolution toward AT-richness was observed in those pericentromeric regions. Furthermore, we showed genetic differentiation between the pericentromeric regions as well as an accelerated rate of evolution in the neo-Y region through the detection of male-specific substitutions by gene sequencing in multiple males and females, and each neo-sex-derived BAC sequencing. CONCLUSIONS: Our results suggest that recombination has been suppressed in the pericentromeric region of neo-sex chromosomes without chromosome rearrangement, whereas high levels of recombination activity is limited in the p...