November 2015 Irish scientific groups in pioneering effort to sequence the genome of the extinct ancestor of modern day cattle

An international group of scientists led by Professor David McHugh from UCD School of Agriculture and Food Science, University College Dublin, with contributions from an SFI research group at NUI Galway, have determined that a now-extinct species of giant wild cattle known as the aurochs crossbred with the ancestors of modern day cattle in Britain and Ireland thousands of years ago.

Published in the leading journal Genome Biology, the scientists used whole-genome sequencing data generated from a 6,750-year-old British aurochs bone discovered in a cave in Derbyshire, England. Standing over six feet tall to the shoulder and weighing more than a ton, aurochs were giant wild cattle that roamed the plains of Europe for thousands of years. The last recorded aurochs died in Poland in 1627.

Researchers Dr Mark Donoghue and PhD student Martin Braud, in the NUI Galway SFI research group of Professor Charles Spillane, contributed to the bioinformatic analysis of the genome data and are all co-authors on the Genome Biology study.

Professor Charles Spillane said: “My research team’s contribution focused on identification of the 700 non-coding microRNA genes in the aurochsen genome to identify variants of these microRNA genes associated with the transition from the wild aurochsen form to the domesticated cattle form we are familiar with today. Until recently it was considered that protein-encoding genes were predominantly responsible for how multi-cellular organisms (such as humans or cattle) are built from a single embryo cell. However, genes which encode for small RNA molecules (not proteins) have emerged over the past decade as an important class of genes that can switch off and on biochemical pathways. Such microRNA genes can be considered as analogous to the conductor in an orchestra, where a miRNA gene can act as the “conductor” of a genetic symphony played out by switching on and off many other genes.”

The distinct genetic differences between the British aurochs and the original cattle of the Near East known as the Fertile Crescent, allowed the researchers to detect the ancient crossbreeding between British aurochs and the early domestic cattle of Britain.

As a result, the researchers conclude that the gene flow from wild aurochs in Britain has significantly shaped the genetic composition of certain breeds of modern British and Irish cattle, in contrast to breeds from mainland Europe.

This information will be particularly valuable for the genome-assisted cattle breeding programmes that underpin dairy and beef cattle breeding in Ireland and other countries.

Ancient heritage or landrace cattle breeds, such as Scottish Highland cattle and Irish Kerry cattle, were found to be most closely related to the British aurochs, a finding that has significant implications for genetic conservation programmes.

It has found that the breeding of wild aurochs with domestic cattle in Britain may have been an important factor in the evolution of these livestock, perhaps through the introduction of desirable traits that helped early domestic cattle to adapt to new environments, such as those encountered in Britain.

The aurochs genome sequence also provides an important comparative reference for a more complete understanding of the genetics underlying important behavioural, production (including milk yield) and health traits in domestic cattle.

High-resolution whole-genome sequence data from 81 animals was directly compared to the aurochs genome sequence to identify key genes that differentiate domestic cattle from their wild counterparts. A parallel approach, using genetic marker data from 1,225 cattle, provided a broader picture of the genomic changes that have shaped the evolution of modern breeds.

The research was part-funded by Science Foundation Ireland and represented an international effort with research contributions from collaborators in UCD, TCD, NUI Galway and IdentiGEN in Ireland, and from international collaborators from the University of Oxford, University of Manchester, the United States Department of Agriculture (USDA), Recombinetics, Inc., and the Beijing Genome Institute (BGI).

To view the Genome Biology paper visit: http://www.genomebiology.com/2015/16/1/234

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