Why women live longer than men

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Washington, Dec 2 (ANI): The reason behind men's limited lifespan is in their sperm, a new study has suggested.

Scientists in Japan believe a particular male gene may explain why men do not live as long as women.

The gene is passed on to offspring by sperm but is only active in men, allowing them to grow bigger bodies at the expense of longevity, according to the study.

Although the study was conducted on mice, scientists think the findings could apply to all mammals including humans.

The researchers looked at mice created with genetic material from two mothers but no father. The 13 'bi-maternal' (BM) mice were produced by manipulating DNA so that the genes in young mouse eggs behaved like those in sperm, giving them the ability to fertilise.

The altered genetic material was then implanted into eggs of adult female mice to create embryos.

Resulting offspring had genes inherited from two mothers, with no contribution made by sperm.M mice were found to live on average a third longer than normal. Normal mice created through natural mating lived no longer than 996 days, while the longest surviving BM mouse lived 1,045 days.

The mice with two mothers were significantly lighter and smaller at birth, and also appeared to have better functioning immune systems.

The gene believed to be responsible is "imprinted" - the name given to the process by which genes inherited from parents are switched on or off in male or female offspring. In this case, the gene is silenced in females when inherited from the father.

"We believe that the most likely reason for the differences in longevity relates to the repression of a gene called Rasgrf1 in the BM mice," study author Professor Tomohiro Kono, director of the Nodai Research Institute in Tokyo, said.

"This gene normally expresses from the paternally inherited chromosome and is an imprinted gene on chromosome 9 associated with post-natal growth," Kono added.

The study has been published online in Europe's leading reproductive medicine journal Human Reproduction. (ANI)

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