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Mitochondrial genes play role in male infertility
By Bijal P. Trivedi

About 75 percent of men who are infertile suffer from oligospermy, a very low sperm count, or from asthenozoospermia, a condition in which many sperm are immotile. Both conditions are untreatable and poorly understood.

A group of researchers in Spain has found genetic variants that correlate with a sperm's ability to swim. Previous studies have proposed that sperm motility is dependent on a molecule called ATP, basically the cellular version of gasoline. When ATP is low there is not enough fuel to power the movement of the tail and propel it towards the egg.

Eduardo Ruiz-Pesini, of the University of Zaragoza in Spain, and colleagues collected semen samples from 545 men in Madrid and Zaragoza, examined the mitochondrial DNA (where some of the ATP producing genes are located) from each sample and sorted them into different categories based on common polymorphisms. The team then assessed the quality of sperm movement within each category. The researchers' findings show that men with group H mitochondrial DNA had normal sperm movement while those with group T had fewer than 25 percent of sperm that could move.

The work is important not only in the field of infertility but also raises the question whether men in category T are predisposed to other diseases.

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Ruiz-Pesini, E. et al. Human mtDNA haplotypes associated with high or reduced spermatozoa motility. Am J Hum Genet 67, 682-696 (September 2000).

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