Genomics
06/12/14 9:48 AM

Sheep's metabolism is related to their skin and wool

The Texel is the breed used to build the sheep genome.
The Texel is the breed used to build the sheep genome.

It has taken eight years to complete the domestic sheep genome. The research unveils unique characteristics of this animals which made them different from the others, like their fat metabolism process that is linked to their skin and wool coat. It also opens up new paths to improve the health of this livestock aiding the development of DNA testing to boost breeding programmes for farmers.

It has taken eight years to complete the domestic sheep genome. The research unveils unique characteristics of this animals which made them different from the others, like their fat metabolism process that is linked to their skin and wool coat. It also opens up new paths to improve the health of this livestock aiding the development of DNA testing to boost breeding programmes for farmers.

"Sheep were one of the first animals to be domesticated for farming and are still an important part of the global agricultural economy. Understanding more about their genetic make-up will help us to breed healthier and more productive flocks," said in a press release professor Alan Archibald of Roslin Institute.

The study, lead by the Chinesse, involves 26 institutions across eight countries –Australia, China, Denmark, France, New Zeland, Saudi Arabia, UK and USA--  that belong to the International Sheep Genomics Consortium. The research, published in the journal Science,  mapped the sheep genome using two Texel sheep –a breed that is important for meat--, a female and a male.

Scientist compared the genetic information to different animals, including goats, cattle, yaks, pigs, camels, horses, dogs, mice, opossums and, of course, humans, and as a result they identify 4,850 single-copy of gene that are shared with other species because they come from common ancestors. This gene were used to build the sheep evolution tree, finding that this animal became a species distinct from goats and other ruminants about four million years ago.

Sheep have a complex, 4-compartmented "stomach" where the largest compartment is the rumen, a specialised chamber that breaks down plant material to make it ready for digestión. This latest is thought to have evolved around 35-40 million years ago.

The surprising thing is that their rumen stomach has a tough keratin-rich surface, a protein that is related to nail production and hair in humans. The composition in the ruen is very similar to skin. According to this study, researchers designated a non-annotated gene, Trichohyalin-like 2 (TCHHL2), and suggested it is specific to mammals. The role of TCHHL2 in sheep would be in cross-linking the keratins at the rumen surface.

Min Xie, Project Manager from BGI, higlighted that "the availability of sheep genome provides us an opportunity to investigate the genetic basis of the rumen evolution and lipid metabolism in sheep skin. Based upon the genomic data in this study, more and more sheep-related studies could be conducted for expanding our understanding on this livestock. It also facilitates the maker-assisted selection for high-quality traits such as wool, meat, milk, among others."

"We investigated the completed genome to determine which genes are present in a process called gene annotation, which resulted in an advanced understanding of the genes involved in making sheep the unique animals that they are," said study senior author Dr Brian Dalrymple of the Commonwealth Scientific and Industrial Research Organisation's Animal Food and Health Sciences.

"Given the importance of wool production, we focused on which genes were likely to be involved in producing wool. We identified a new pathway for the metabolism of lipid in sheep skin, which may play a role in both the development of wool and in the efficient production of wool grease (lanolin)."

In that respect, researchers found a gene related to the family of those genes who are involved in the creation of cornified envelope, and named it LCE7A. The researchers thought the expansion of LCE7A --which is also expressed in skin of the sheep-- was associated with the wool formation. They also assumed that other gene called MOGAT in sheep skin may facilitate wool production.

The collaborating countries and research institutes were: Australia (CSIRO; University of New England; University of Sydney), China (BGI-Shenzhen; Inner Mongolia Agricultural University; Institute of ATCG, Nei Mongol Bio-Information; Kunming Institute of Zoology; Lanzhou Institute of Husbandry and Pharmaceutical Science; Macau University of Science and Technology; North West A&F University; Sichuan Agricultural University), Denmark (University of Copenhagen), France (INRA), New Zealand (AgResearch; University of Otago), Saudi Arabia (King Abdulaziz University), UK (Biosciences KTN; Edinburgh Genomics; European Molecular Biology Laboratory, European Bioinformatics Institute; The Roslin Institute; Wellcome Trust Sanger Institute; University of Edinburgh), USA (Baylor College of Medicine; USDA-ARS Animal Disease Research Unit; Utah State University; Washington State University).

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