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
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