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Sperm Proteins Could Reveal the Secrets of Male Infertility and of the Origin of the SexDecoding made proteins is on the run with Drosopila |
By Stefan Anitei, Science Editor
13th of November 2006, 08:43 GMT
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British scientists have made the first characterization of the protein compounds in an evolved eukaryotic cell (with DNA inside a nucleus).
Till now, 381 proteins were uncovered in the fruit fly's (Drosophila melanogaster) sperm (photo) and there are more to be described.
The "proteome" (totality of the proteins) includes everything the sperm needs to survive and function correctly, and the researchers want to discover which are behind the capacity of some sperms to be more successful than others.
Around 50 % of the genes of the fruit fly sperm proteome have a counterpart in mammals (humans included), thus, this study could shed some light on male infertility in mammals.
Comparisons between sperm proteome of the fruit fly with other species will elucidate some evolutionary link and could explain more about the origin of the sexual reproduction, because proteins
control all that makes a organism work, from "bricks" in constructing all living structures (at least in animals, because plants contain primarily cellulose and polysaccharides) to catalysts in the biochemical reactions.
"This is the first catalogue of sperm proteins for any organism, and it offers a tantalizing glimpse into how we might begin to answer some of biology's most fundamental questions," said Dr Tim Karr from the University of Bath.
"Amazingly we know very little about what is in a sperm, which probably explains why we don't really understand sex, let alone how it evolved."
"Being able to compare the structure and content of the proteomes of sperm from different species should help us understand the evolution and origin of sperm."
"We now know of at least 381, which is a greater than 50-fold increase in our knowledge base. Now that we have identified them, we should be able to study the function of all of these."
Previous studies had counted for the number of proteins found on sperm separated into 'spots' on a special gel matrix, but this revealed only the protein number without identifying each protein composition.
"The sperm proteome provides a basis for studying the critical functional components of sperm required for motility, fertilization and possibly early embryo development," said Dr Steve Dorus, also from the University of Bath.
"It should be a valuable tool in the study of infertility as more targeted studies can now be established in model organisms."
"Furthermore, having a comprehensive catalogue of proteins to compare between different species will reveal how natural selection has impacted sperm evolution."
"We can start to look for the 'core' sperm proteome - that is, the most basic required constituents of sperm. This will not only shed light on the evolutionary origins of sperm, but may advance our understanding of the evolution of sex itself."
The scientists are eager to understand more about sperm competition, a phenomenon that has puzzled them for years: what makes one sperm more successful at reaching and fertilizing the egg than those of other males of the same species. "If we can work out what makes one sperm more successful than another, we might be able to apply this knowledge to clinical therapies for the treatment of sperm that are not functioning properly." said Dr Karr.
The researchers have found that, beside DNA which is the genetic information that sperm cells transmit to the offspring, sperm also transports RNA with a direct influence on fertilization and embryo development.
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