Summary
The horse reference genome from the Thoroughbred mare
Twilight has been available for a decade and, together with
advances in genomics technologies, has led to unparalleled developments in
equine genomics. At the core of this progress is the continuing improvement of
the quality, contiguity and completeness of the reference genome, and its
functional annotation. Recent achievements include the release of the next
version of the reference genome (EquCab3.0) and generation of a reference
sequence for the Y chromosome. Horse satellite-free centromeres provide unique
models for mammalian centromere research. Despite extremely low genetic
diversity of the Y chromosome, it has been possible to trace patrilines of
breeds and pedigrees and show that Y variation was lost in the past ~2300 years
due to selective breeding. The high-quality reference genome has led to the
development of three different SNP arrays and whole genome sequences (WGS) of
almost 2000 modern individual horses. The collection of WGS of hundreds of
ancient horses is unique and not available for any other domestic species. These
tools and resources have led to global population studies dissecting the natural
history of the species and genetic makeup and ancestry of modern breeds. Most
importantly, the available tools and resources, together with the discovery of
functional elements, are dissecting molecular causes of a growing number of
Mendelian and complex traits. The improved understanding of molecular
underpinnings of various traits, continues to benefit the health and performance
of the horse while also serving as a model for complex disease across
species.