Submitted September 22, 2007
Returned for revision October 18, 2007
Accepted January 23, 2008
Male Reproductive Tract
Prm3, the Fourth Gene in the Mouse Protamine Gene Cluster, Encodes a Conserved Acidic Protein That Affects Sperm Motility
Pawel Grzmil *,
Dagmara Boinska ,
Kenneth C. Kleene ,
Ibrahim Adham ,
Gregor Schlüter ,
Martin Kämper ,
Byambajav Buyandelger ,
Andreas Meinhardt ,
Stephan Wolf ,
and
Wolfgang Engel
* To whom correspondence should be addressed. E-mail: pgrzmil{at}gwdg.de.
Abstract
The protamine gene cluster containing the Prm1, Prm2, Prm3 and Tnp2 genes is present in human, mouse and rat. The Prm1, Prm2 and Tnp2 genes have been extensively studied, but almost nothing is known about the function and regulation of the Prm3 gene. Here we demonstrate that an intronless Prm3 gene encoding a distinctive small acidic protein, is present in 13 species from seven orders of mammals. We also demonstrate that the Prm3 gene has not generated retroposons, which supports the contention that genes which are expressed in meiotic and haploid spermatogenic cells do not generate retroposons. The Prm3 mRNA is first detected in early round spermatids, while the PRM3 protein is first detected in late spermatids. Thus, translation of the Prm3 mRNA is developmentally delayed similar to the Prm1, Prm2 and Tnp2 mRNAs. In contrast to PRM1, PRM2 and TNP2, PRM3 is an acidic protein which is localized in the cytoplasm of elongated spermatids and transfected NIH-3T3 cells. To elucidate the function of PRM3, the Prm3 gene was disrupted by homologous recombination. Sperm from Prm3-/- males exhibited reductions in motility, but the fertility of Prm3-/- and Prm3+/+ males is similar in matings of one male and one female. We have developed a competition test in which a mutant male has to compete with a rival wild type male to fertilize a female; the implications of these results are also discussed.
Key words:
Sperm motility and transport •
Spermatogenesis •
protamine gene cluster •
retroposon •
sperm competition
