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An atlas for sheep DNA

The Sheep Atlas is a map to show where genes are in the sheep's genetic make-up, and what they control.

Sheep in a field
We analysed DNA from these sheep that are a cross-breed between Scottish Blackface and Texel sheep.

Genes play a crucial role in animal development, from disease susceptibility to coat colour. Sheep have more than 20,000 genes in their DNA, which are switched on or off at different stages and in different parts of the body. Knowing when and in what tissues this happens helps us to understand how a lamb grows into a healthy adult sheep.  

A team of Roslin researchers produced the Sheep Gene Atlas, a map to show where the genes are in the sheep genetic make-up (genome), and what they control. Scientists all over the world can access it for free. 

By developing the Sheep Gene Atlas, scientists have learned more about the genes that influence sheep health and the production of meat and wool, and new information about genes that were not previously understood. The sheep atlas will help to guide future sheep breeding programmes, improving flocks across the world.

Why are genes important? 

Genes are segments of DNA that contain instructions and are used by the cell to make different proteins. The genome includes the sum total of genes in an individual. At different times during development, different genes are turned on and off as needed. Proteins made by cells work together to coordinate the process of development and direct cells in how to build everything our body requires. A missing or altered gene can cause disease, affect how an animal responds to infection or change the role and appearance of a tissue or cell type. An altered gene in Texel sheep for example, gives them a muscular appearance.

Detailed knowledge of what genes are, what each one does, and when and where the body uses them can help in our understanding of disease susceptibility and other characteristics, and in livestock help to guide our selection of hardy or more productive animals.

 

Sheep are a central part of the rural economy in the UK and are essential to sustainable agriculture across the globe.  This new resource represents a major step towards understanding how the sheep’s genetic information influences its physical characteristics and provides a foundation to use this information to generate sustainable improvements in the productivity of livestock animals.

Dr Emily ClarkSheep Atlas Project Coordinator, Roslin Institute
A Meru Graph representing the gene expression across all sheep tissues
Pictured is an image from the Sheep Gene Atlas, showing major groups of genes (dots) and how they are connected (lines). Genes are considered connected when they are expressed at the same time, nearby to one another in the same tissue (e.g. liver) or type of cell (e.g. macrophage). These ‘co-expression’ patterns can tell us a lot about the function of genes, and provide information about genes that previously had no known function.

Why study the sheep genome?

Sheep are an important economic resource in the UK, but we know relatively little about the genes controlling important characteristics in sheep compared with other species. We know much more about humans, cattle and even some microbes!

A better understanding of the genes controlling important characteristics in sheep will have positive effects on the UK economy, if we can breed sheep with genes that make them more productive and more resistant to disease, we would improve the national flock overall.

How was the sheep atlas made?

Samples were collected from three male and three female Texel  crossed with Scottish Blackface adult sheep, and nine lambs at different stages of development. RNA (a form of genetic message made by active genes) was extracted from each sample. In the study nearly 500 samples and 2,255,734 genetic messages were individually analysed! Needless to say, this was a big undertaking.

Lots of genes are shared between sheep and other species, including other ruminants such as cattle, and even humans. This allows us to identify genes in the sheep genome that have already been found and defined in other species. Different versions of these genes and the times that they are active can help us to understand why species are different, for example, in how they respond to disease. We are now working on comparing how genes are switched on and off in goat immune cells and comparing this information with our gene atlas for sheep.

Who can use the Sheep Atlas?

The Sheep Atlas is free for anyone in the world to use, the information can be used by scientists globally as well as in the UK, to understand the genes controlling many different important characteristics in sheep, and as a foundation for using this type of information to inform sheep breeding programmes.

Further Reading

Sheep gene insights could help farmers breed healthier animals

Scientific Publication