Mystery of male infertility closer to being solved

Researchers in Australia and Britain have burrowed down to the gene level to find a little known protein with a powerful impact on how well sperm can swim. Males with a mutated RABL2 gene in their sperm were “outwardly healthy, had normal body weights and displayed normal mating behaviour,” the researchers reported.

The critical difference, however, was that the RABL2 sperm tails were 17 per cent shorter, so they conked out before they could fertilize the female’s eggs. “What’s remarkable is that the defects seem to be quite specific in the sperm,” co-author Dr. Mark Field, a cell biologist at the University of Cambridge, told Torstar News Service. The research, he said, “is pretty conclusive in going forward with the biology. We can start to look at the way that particular gene operates. “This is opening the door. There is a lot more that one needs to do.”

Sperm tails are different from other cilia, or hairlike structures: they have an outside cover and dense fibres, which protect them and let them steer into the female reproductive canals. Tamper with that and you tamper with fertility, the study concluded. “The mutations in the RABL2 gene are very likely to cause infertility,” said lead author Dr. Moira O’Bryan of Monash University in Australia, where she leads laboratory research on sperm development and the genetics of male infertility. Her work also uncovered a 50 per cent drop in sperm production traced to the mutated RABL2 gene.

One in 20 men of reproductive age is believed to be infertile for a variety of reasons, but most of those reasons are a mystery. Male infertility accounts for half of the cases of couples unable to conceive. The discovery presents not just the basis for understanding male infertility, said O’Bryan. It also opens the door to “options for urgently needed male contraception.” Researchers decided to examine RABL2 because a lot of it is found in sperm. But because it is also found in other tissues, such as the brain, kidney and liver, any male contraceptive pill would have to target male reproductive organs, said O’Bryan.

Discovery of damaged RABL2 genes and male infertility could also be a sign of gene problems in those other organs, she said. “Many of the basic processes of sperm development occur at lower levels in other organs of the body,” she said. Treating a man for infertility “offers the opportunity not only to give him the children he desires but also to mitigate future diseases.”

Metro News Canada

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