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Set adrift: gene mutation can stop sperm from swimming

15 October 2012
Appeared in BioNews 677

A gene mutation has been associated with sperm motility and production, offering new insights into male infertility.

Researchers in Australia and the UK found that mice with a mutated copy of the gene RABL2 had sperm with tails that were 17 percent shorter than normal, making them less able to 'swim'. The mutated gene also led to a 50 percent decrease in sperm production, the results showed.

'The mutations in the RABL2 gene are very likely to cause infertility', said Professor Moira O'Bryan, who led the research. 'Further, as motility is absolutely essential for fertility, insights into tail function may reveal options for urgently needed male-based contraception', she continued.

The lead author on the paper, Jennifer Lo, a PhD candidate at Monash University's School of Biomedical Sciences, said that RABL2 works with other molecules called intraflagellar transport proteins, which carry proteins required for proper sperm function down the tail.

'Intraflagellar transport proteins are like a train', explained Lo. 'Our data suggests that the reloading of the train is defective if RABL2 dysfunctions'.

With dysfunctional RABL2, once the proteins that are needed for tail function are depleted, they are not fully replaced. This leads to a decrease in tail length and an overall reduction in sperm number.

'The train is still running in sperm tails with dysfunctional RABL2, but it contains fewer passengers. The end result is that sperm formation and motility are abnormal'.

As RABL2 dysfunction affects the motility and the production of sperm, the inhibition of RABL2 could lead to a functioning male pill. A problem with targeting this gene is that other areas of the body, such as the kidneys and brain, also have copies of RABL2. To achieve the desired temporary infertility, a gonad-specific treatment will have to be produced.

The study is published in PLOS Genetics.

Fertility discovery a sperm's tail
Monash University (press release) |  7 October 2012
Gene discovered which stops sperm swimming
Daily Telegraph |  9 October 2012
Off with their tails! Male contraceptive pill a step closer as scientists find a way to stop sperm swimming
Mail Online |  9 October 2012
RAB-Like 2 Has an Essential Role in Male Fertility, Sperm Intra-Flagellar Transport, and Tail Assembly
PLOS Genetics |  4 October 2012
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