Quick Dips

Hunting for Twins

An Australian medical researcher is looking for something sheep scientists in New Zealand have been interested in for many years -- exactly what gene causes twinning.

Dr Nicholas Martin, a genetic scientist and principal research fellow with the Queensland Institute of Medical Research in Brisbane, has turned to New Zealand to find women who may be able to help isolate the twinning gene. He wants to contact sisters who have both produced twin offspring so he can study the women's genetic composition through their DNA. The sets of twins must be non-identical, and must have been produced naturally and not through fertility programmes.

Producing sets of fraternal twin cousins naturally is unusual, but New Zealand Multiple Birth Association birth register co-ordinator Joy Brown has, on Martin's behalf, already managed to contact from this area several women from the same family who have had twins. In one case, there were four sisters from one family who all produced twins.

They are also looking for families with a strong history of twinning or multiple births. Extended family members from the same blood line of relations with twins may also be carrying a twinning gene, and be able to provide essential genetic information for scientists to make the necessary link.

Martin says twins provide geneticists with a wonderful opportunity in research projects. In particular, he's hoping his work will lead to isolating the twinning gene in humans. The research will also contribute to a world-wide human gene map, which basically records the order genes are found on the human chromosome, and what these genes are responsible for.

This research is a parallel of studies being done by AgResearch Invermay into prolific lines of sheep. Producing twins or multiple births is influenced by genes, so understanding more about the twinning genes and isolating them in one species therefore benefits studies in other species.

Both Martin and AgResearch Invermay are conducting research into prolificacy genes and contributing their knowledge on these genes to a world-wide gene map, on the human and the sheep genomes respectively. AgResearch Invermay is helping the human research through its expertise in extracting DNA from blood samples.

The easiest way for Martin to receive samples from women in the trial is to have their DNA sent over to him. And because extracting DNA from blood samples is basically the same procedure for any species, human or sheep, blood samples from the Australian trial are being sent to experts at AgResearch's Molecular Biology Unit in the Biochemistry Department at Otago University. The DNA is extracted from these samples before being sent on.

AgResearch has already discovered genes in sheep which influence the number of lambs born. One gene known as the Booroola sheep gene produces 100 extra lambs from 100 ewes, or 150 lambs from 100 ewes with two copies of the gene, while the Inverdale gene will produce an extra 60 to 70 lambs from 100 ewes. Research is continuing at Invermay to find further genes which have a lesser effect on prolificacy.

Women taking part in the research are only required to provide one blood sample, and information about twinning in their family, and will be kept up-to-date on research findings from Brisbane. All information will be treated in the strictest confidence. Please contact Joy Brown, New Zealand Multiple Birth Association birth register co-ordinator in Invercargill, phone (03) 216-7356, for further information on the human twinning studies.