Satellitome analysis on Microtus thomasi (Arvicolinae) genome, a mammal species with high karyotype and sex chromosome variations

The voles of the Microtus thomasi / M. atticus species complex (Arvicolinae) display extensive karyotypic variation, in the number of autosomes and the morphology of sex chromosomes. We analysed the satellitome of M. thomasi and identified 17 satDNA families, corresponding to 6.704% of the genome. Homogenization and divergence analyses showed that some satDNA families are more homogeneous, indicative of recent amplification, while others displayed higher variation, suggesting ancient amplification. Twelve of satDNA families are conserved across Arvicolinae with a substantial variation in the abundance and the composition. These results supports the "library" hypothesis, where a shared collection of satDNAs exists across related species, with differential amplification driving species-specific genomic profiles. Localization analysis demonstrated that an increased number of satDNA families are localized in the pericentromeric and the heterochromatic regions of autosomes and sex chromosomes. Our results suggest that the heterochromatin of the X and Y chromosomes co-evolved and that satDNA families might have contributed to the chromosomal rearrangements involved in the karyotypic variation and sex chromosome polymorphism of the chromosomal races. Our study contribute to a deeper understanding of the evolutionary mechanisms underlying karyotype diversification in Microtus species, which exhibit some of the highest rates of karyotypic variation among mammals.