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News - Genes that raise the chances of non-identical twins identified

29th April 2016

Gene variants that increase by 29 per cent a woman’s chance of giving birth to non-identical twins have been identified in a breakthrough international collaboration by researchers from Queensland, Iceland, Netherlands and the US.

Associate Professor Dale Nyholt from the QUT Institute of Health and Biomedical Innovation (IHBI) said the identification of the two DNA variants associated with a higher chance of dizygotic, or non-identical, twins had also shed light on the mechanisms of female fertility.

The research findings are published today in the American Journal of Human Genetics

“Dizygotic twins develop from two separate eggs that have emerged from separate ovarian follicles at the same time and been fertilised by separate sperm cells,” said Professor Nyholt, who heads the Statistical and Genomic Epidemiology Laboratory in IHBI.

“Two thirds of twins are non-identical pairs and they are as genetically alike as their other siblings. Identical, twins, in contrast, share the same genetic makeup because they are the result of one embryo splitting in half.”

Professor Nyholt said the research team’s findings had advanced understanding of women’s fertility and infertility by identifying key mechanisms controlling function of the ovaries.

“We found one variant is close to the gene coding for the secretion of the hormone that stimulates ovarian follicles to release an egg and the second variant is in a location likely to be involved in the ovaries’ response to follicle stimulating hormone,” he said.

“When both variants are present, a woman has a 29 per cent greater chance of having non-identical twins.”

Professor Nyholt said one of the gene variants also had significant effects on other fertility measures including the age of a girl’s first period, age at menopause, number of children, and the age at first and last child.

“It also affects the genes behind polycystic ovary syndrome, which is a major cause of female infertility,” he said.

“This discovery will help research on the response to hormone stimulation for assisted reproduction such as IVF.”

While there are more genes to be found that influence non-identical twin birth, Professor Nyholt said that in future, a simple gene test could be developed to identify women at risk of a strong response to hormonal treatment that could prevent the serious complication of ovarian hyperstimulation syndrome.

The International collaboration includes researchers from Europe: Australia (QUT QIMR Berghofer Medical Research Institute, University of Queensland), Iceland (deCODE), The Netherlands (Vrije Universiteit Amsterdam and VU Medical Centre), and the USA (the Avera Institute for Human Genetics in Sioux Falls and Minnesota Center for Twin and Family Research).

Please site this article in press as: Mbarek et al., Identification of Common Genetic Variants Influencing Spontaneous Dizygotic Twinning and Female Fertility, The American Journal of Human Genetics (2016), http://dx.doi.org/10.1016/j.ajhg.2016.03.008.

 

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