Tracking Down Sperm's Last Push Into Egg...

Sperm 092015

That of the many million sperms, only 1 sperm will succeed in penetrating the egg, released by the ovary into the fallopian tube, is a basic fertilization fact.

In a first, Patricia Martin-DeLeon, a reproductive biologist at the University of Delaware, and her team have revealed as to what happens just before the sperm's entry into the egg. The research was conducted in mice using a high-powered, three-dimensional super-resolution microscope.

"There is communication between the sperm and the fallopian tube that helps prepare the sperm for its big push into the egg," says DeLeon.

According to the researchers, "oviductosomes", found in secretions from the fallopian tube accumulate primarily on the sperm's head and the midpiece of its tail, facilitated by membrane receptors known as integrins. After attaching to the sperms, the oviductosomes deliver critical molecules like RNA, lipids and plasma membrane Ca2+-ATPase 4, a transport protein, to the sperm, enabling the sperm to penetrate into the egg.

"The Ca2+-ATPase 4, also known as the plasma membrane calcium pump, is required by the sperm just prior to fertilization, as well as in the early embryo. The sperm pumps out calcium and takes in hydrogen ions, which seems to give it that last push into the egg, and also is critical to starting the zygote's life", noted DeLeon.

The researchers are optimistic that the discovery of oviductosomes and the knowledge about the critical molecules they carry to the sperm would help in improving the efficiency of IVF (in vitro fertilization). The current success rate for IVF in the U.S. is said to be roughly 25-30%.

The research is published in the Journal of Biological Chemistry



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