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Why women live longer than men | 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. BM 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. |
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