Teagasc Breakthrough on Sheep Could Have Big Impact on Human Fertility Research

Issued 12 August

A new breakthrough on sheep fertility by scientists at the Teagasc research centre at Athenry, Co. Galway, could have major significance for research on control of fertility in women.

A team of researchers, led by Dr Seamus Hanrahan of Teagasc Athenry, has identified three new gene mutations which have a profound effect on ovarian function. As well as having significant potential benefits for sheep production, Dr Hanrahan says the discovery is likely to provide important insights for human fertility.

Using DNA technology, the scientists have found two distinct genes with a large effect on ovulation rate in sheep. Two different mutations have been found in one of these genes.

"One of the genes is on the X-chromosome and therefore males can only inherit it from their mother. In the case of the second gene, individuals can inherit it from either parent. We are the first group of researchers in the world to have discovered that this second gene affects ovulation rate in sheep", said Dr Hanrahan.

"Ewes that inherit a single copy of any of the three mutations have a significantly higher ovulation rate. The effect could be an increase in litter size of between 0.5 and 1 lamb per ewe. Only improvements at the lower end of the scale would be practical under Irish sheep production conditions", he said.

From a human perspective, the most significant discovery is that ewes which inherit two copies of any of these gene variants are sterile, because the normal development of the follicles in the ovary is blocked.

"This profound effect on ovarian function makes this discovery of major potential significance to medical research on fertility control in women. It is likely that what we have discovered on how follicle development is controlled in sheep will provide important insights for human fertility", said Dr Hanrahan.

He said that the newly identified genes operate differently to the equivalent genes in mice, which are used as models to assist in understanding human reproductive problems

"The fact that the `mouse model' does not apply to sheep may also mean that it is not really applicable to humans", said Dr Hanrahan.

This research project, which involves collaboration between Teagasc Athenry and scientists in NUI Galway, France and New Zealand, is part of an expanded Teagasc programme in biotechnology research. Dr Hanrahan says the results could also lead to new opportunities for the application of molecular genetic biotechnology to enhance the reproductive capacity of cattle.

"Future research on these natural variations in gene function will undoubtedly enhance the overall understanding of reproduction", he said.