Sperm mRNA found in eggs
Presence in newly fertilized ova provides insight into parthenogenesis and
cloning
By Cathy Holding

A team of researchers has observed sperm mRNA in newly fertilized eggs,
according to a paper published in the May 13 Nature, in a finding that
provides alternative explanations for mammalian parthenogenesis, cloning,
and male infertility, the team writes. The results would also have immediate
applications for treating infertile couples and for providing a screen for
toxicological effects in spermatogenesis, said coauthor Steven Krawetz.

Krawetz's team identified six transcripts present in sperm, but not in
unfertilized eggs, and followed the delivery of two of them-clusterin and
protamine-2-into eggs using real-time reverse transcriptase polymerase chain
reaction.

"It's really the first demonstration that human sperm contain a population
of RNAs," said Krawetz, a professor in the Department of Obstetrics and
Gynecology at Wayne State University. "Specifically, we show messenger RNAs,
and those are delivered to the oocyte upon fertilization."

The mRNA must exist before the single fertilized zygote has divided into
four and then eight cells, Krawetz told The Scientist. "After [that], you
have activation of the embryonic genome, and that takes over," he said. "So
the egg has its own store of mRNA, and now we show that the sperm has its
own store of mRNA."

Krawetz believes that the type of assay developed in the paper can produce a
fingerprint of the RNAs present in spermatozoa that could be used to examine
differences between fertile and infertile male individuals. "We'll be able
to critically examine the role of the male," he said. In addition, the team
is hoping to take this fingerprint technology "to the next level" by
providing a screen for different toxicological effects to which a male may
have been exposed, he said.

"We completely agree that the paternal fingerprints are obviously concerned
at several steps," said Serge Carreau, director of the Institut de Biologie
Fondamentale et Appliquée at the Université de Caen Basse-Normandie in
France, "not only at oocyte fertilization, as this paper said. but also we
have found that the human spermatozoa is equipped in terms of specific mRNAs
that are really also concerned with the quality of the sperm, for motility,
and the acrosome reaction."

Read the rest at TheScientist.com
http://www.biomedcentral.com/news/20040513/01

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