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Researchers at Shanghai's Fudan University announced the discovery of the world's first genetic link for human infertility. This breakthrough came when studying the movement of the SUN1 protein contained in the nuclear membrane of mice cells since 2003. When the protein was broken down, the disruption halted the usual pairing and recombination of chromosomes during the reproduction process among sexual cells.

Mice thus born with a broken SUN1 protein had markedly smaller testes and ovaries than normal mice which impaired the production of sperm or eggs, explained researchers.

"We can infer that the SUN1 protein plays a key bridging role in the reproductive process of mice, which also provides a target point for the diagnosis of human infertility," said Ding Xu, a PhD researcher at the institute and the article's lead writer.

Scientists uncovered the pairing and recombination process of chromosomes long ago, although light had so far not been shed on the process' initiating factor.

"A genetic reason for most infertility has been ambiguous for a long time," said Xu Ren'er, an associate professor and co-author of the article.

Ten percent to 15 percent of the world's couples suffer infertility problems and worsening environmental pollution, among other factors, may drive this number upwards.

As mice and humans share about 99 percent of reproduction genes, "the finding is expected to provide a new clue for human beings to understand the reason for the disorder," Xu said.

However, he sought to quell any enthusiasm by saying this finding was still a long way off from being applied to treating human infertility.

The breakthrough was published in Developmental Cell, a leading international biology journal, on Monday and is set to be reproduced in the respected academic journal Science on Friday.

(Shanghai Daily June 6, 2007)