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Study finds reproductive mechanism causing genetic change

Aug 31 2016

Professor Brett Nixon

Researchers from the University of Newcastle (UON) have charted a novel mechanism within the male reproductive tract that can alter a sperm’s genetic cargo because of external factors like obesity and stress.

For men aiming to start a family, it confirms that a healthy lifestyle can influence sperm performance at the time of fertilisation and ultimately the health of their offspring and multiple generations to follow.

Professor Brett Nixon, a research fellow from HMRI’s Pregnancy and Reproduction Program, says his team responded to mounting evidence that sperm microRNA profiles are altered by exposure of the father to dietary, physiological and environmental factors.

“Our study focused on the mechanism because knowing where and when changes occur to microRNA within sperm can help explain why obese or stressed fathers, for example, pass on the phenotype,” Professor Nixon said.

“We wondered if it happened during sperm development in the testes, where the differentiation of the cell occurs, or as they pass through the male reproductive tract where functional maturation takes place.

“That’s important because, typically, when a sperm leaves the testes they can’t manufacture any more of their own RNA species. But the male reproductive tract can communicate to the maturing sperm cells and deliver molecules such as proteins which subsequently play a role in initiating motility and giving the sperm the ability to recognise the egg.”

As reported in the international Nature journal Scientific Reports, the research team found that the microRNA within mice sperm can be altered by as much as 75 per cent as they travel down the reproductive tract, driven by external forces.  

This intercellular communication has important epigenetic implications for the embryo since microRNA regulate the function of genes.

“We’re not certain whether every sperm is affected though I would imagine that it’s the majority,” Professor Nixon added. “But with obesity, for example, research has shown that by exercising the fathers for a short time they can reverse some of the changes and restore normal composition of the sperm–borne microRNA.”

“We’re at the tip of the iceberg … we know where it occurs but not why. The next step is to incorporate different disease and stress models to test this mechanism in more depth.”

* The UON research team included Jackson Reilly, Eileen McLaughlin, Simone Stanger, Amanda Anderson, Kiralee Church and Bettina Mihalas. Professor Brett Nixon researchers in conjunction with HMRI’s Pregnancy and Reproduction Program. HMRI is a partnership between the University of Newcastle, Hunter New England Health and the community.