Rapid Interspecific Evolution of the Ampliconic Regions on Felid Sex Chromosomes

The ampliconic regions of mammalian sex chromosomes are among the most rapidly evolving in the genome. The highly repetitive nature of these regions makes them exceedingly difficult to sequence using modern short-read WGS approaches, and, as a result, has led to their absence from all but a handful of current genome assemblies. This is troubling as these regions have major implications in meiotic drive systems, male fertility, and inter-specific hybridization. We have used an integrated approach combining cDNA libraries, RNA-Seq, FISH, BAC clone sequencing, and bioinformatic analyses to examine sex chromosome evolution within the cat family Felidae. Using this multi-pronged approach we have sequenced several ampliconic regions of the domestic cat sex chromosomes; uncovering several multi-kilobase, gene-rich repeated units. We have also identified several novel, often massively amplified, gene families, and uncovered copy number variations of these genes, as well as variations in previously reported ampliconic genes, between species across the phylogeny of Felidae. These results will aid in the identification of regions responsible for hybrid male sterility – a common early barrier to nascent species hybridization and thus an important mechanism in the evolution of new species.