AgResearch has achieved a major world first by discovering the gene in Inverdale sheep that causes them to be more prolific.

Discovery of this sheep gene, which has a major impact on fertility, will not only have a huge impact on New Zealand’s sheep farms but will also have very exciting potential for human fertility and opens up major opportunities for further scientific discoveries.

A group of AgResearch scientists led by Dr Sue Galloway has discovered that mutations in a specific gene, known as GDF9B, influences prolificacy. Female sheep with one copy of the mutation have increased fertility (i.e. ovulation rate) whereas those with two copies of the mutation are actually infertile.

The discovery is an ideal example of the life sciences in action and of New Zealand moving from a traditional agricultural base into the knowledge economy, said Dr Galloway.

Internationally, this discovery is a major scientific coup which again puts New Zealand firmly at the forefront of sheep gene research. The exciting discovery is being published in the prestigious international science journal Nature Genetics, a rare feat for New Zealand scientists.

The finding also is a demonstration of how an effective interdisciplinary collaboration between relatively small research groups can lead to major scientific achievements. AgResearch’s collaboration with a science group in Finland, which specialises in human fertility research, will ensure the discovery will be exploited to its fullest potential in human medicine.

The gene is a natural way for sheep farmers to increase on-farm productivity by producing more lambs from the same number of ewes. The discovery also enables AgResearch to develop an exact gene test which will identify fertile carrier ewes and rams.

It also offers very positive hope for the development of a form of possum control for New Zealand based on the potential for blocking fertility.

The discovery provides new understanding of mechanisms for regulating mammalian female reproduction and has significance for developing conceptually new infertility treatments and contraceptives.

It is the first time ever a gene has been discovered acting directly to increase egg production on the ovary rather than through the pituitary gland in the brain. This in itself is a major scientific discovery and one that opens a whole new branch of research and opportunity.

The discovery is the culmination of over a decade of major AgResearch studies into prolificacy in sheep, involving a group of scientists, as well as some observant New Zealand farmers.

AgResearch scientists had previously recognised that a significant gene, named Inverdale, was having a big impact on prolificacy in some research flocks, and this has formed the basis of the research leading up to the discovery. AgResearch scientist George Davis’ careful breeding work, observation and monitoring of the Inverdale gene, with assistance from two enlightened farmers, had already made it possible to map the position of the gene on the X chromosome using genetic markers.

The recent discovery means AgResearch scientists have now proven the GDF9B gene, already discovered in humans and mice, is what has been producing the Inverdale effect in their research flocks.

Mapping the Inverdale gene, along with other sheep genes, has established the AgResearch Molecular Biology Unit, based in the Department of Biochemistry at Otago University, as a world leader in sheep gene mapping and discovery.

Ewes with one copy of the gene have on average one more ovulation than usual, but those with two copies of the gene have abnormally small ovaries (streak ovaries) and are infertile. Understanding more about how these ovaries develop in sheep will provide the scientists with invaluable information to base new discoveries on.

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