It had been believed for decades that spermatozoa are translationally silent. However, Dr. Yael Gur and Haim Breitbart (Bar-Ilan University, Israel) now show that, in fact, protein translation does take place in mammalian sperm prior to fertilization.
Their paper has been released online ahead of print at www.genesdev.org.
After ejaculation, sperm reside in the female reproductive tract for several hours. During this time, a number of biochemical changes take place within sperm, collectively known as "capacitation," that render the sperm competent to penetrate and fertilize the female oocyte.
In their new report, Drs. Gur and Breitbart demonstrate that human, rat, bovine and mouse sperm all incorporate labeled amino acids into polypeptides during the capacitation phase. They identify that mitochondrial translation machinery (as opposed to cytoplasmic) directs translation of nuclear-encoded genes in sperm, and that its inhibition leads to a marked decrease in sperm motility, actin polymerization, the acrosome reaction and in vitro fertilization rates.
Thus, protein translation in sperm is essential for sperm functions that directly contribute to fertilization. Dr. Breitbart is confident that "The new findings would give us better understanding for treatment of male infertility and developing new male or female contraceptives."