EquCab3, an Updated Reference Genome for the Domestic Horse

Abstract

EquCab2, a high-quality reference genome for the domestic horse, was released in 2007. Since then, it has served as the foundation for nearly all genomic work done in equids. Recent advances in genomic sequencing technology and computational assembly methods have allowed scientists to improve reference assemblies of large animal and plant genomes in terms of contiguity and composition. In 2014, the equine genomics research community began a project to improve the reference sequence for the horse, building upon the solid foundation of EquCab2 and incorporating new short-read data, long-read data, and proximity ligation data. The result, EquCab3, is presented here. The count of non-N bases in the incorporated chromosomes is improved from 2.33Gb in EquCab2 to 2.41Gb from EquCab3. Contiguity has also been improved nearly 40-fold with a contig N50 of 4.5Mb and scaffold contiguity enhanced to where all but one of the 32 chromosomes is comprised of a single scaffold.