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BOR - Papers in Press, published online ahead of print June 21, 2006.
Biol Reprod 2006, 10.1095/biolreprod.106.052712
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BIOLOGY OF REPRODUCTION 75, 588–597 (2006)
DOI: 10.1095/biolreprod.106.052712
© 2006 by the Society for the Study of Reproduction, Inc.

Research Article

Ontogeny of Tyrosine Phosphorylation-Signaling Pathways During Spermatogenesis and Epididymal Maturation in the Mouse1

Minjie Lin 3, Yun Hwa Lee 3, Weian Xu , Mark A. Baker , and R. John Aitken 2

Centre for Reproductive Science and Australian Research Council (ARC) Centre of Excellence in Biotechnology and Development, School of Environmental and Life Science, University of Newcastle, Callaghan, New South Wales 2308, Australia

ABSTRACT

The objectives of this study were to map the ontogeny of tyrosine phosphorylation signal transduction pathways during germ cell development and to determine their association with the differentiation of a functional gamete. Until testicular germ cells differentiate into spermatozoa, cAMP-induced tyrosine phosphorylation is not detectable. Entry of these cells into the epididymis is accompanied by sudden activation of the tyrosine phosphorylation pathway, initially in the principal piece of the cell and subsequently in the midpiece. In the caput and corpus epididymides, the potential to express this pathway is inhibited by the presence of calcium in the extracellular medium. However, calcium has no effect on the expression of this pathway in caudal epididymal sperm. The competence of these cells to phosphorylate the entire sperm tail, from the neck to the tail-end piece, is accompanied by a capacity to exhibit hyperactivated motility on stimulation with cAMP. A distinctly different pattern of tyrosine phosphorylation, involving the acrosomal domain of the sperm head, is invoked as spermatozoa enter the caput epididymis, and phosphorylation remains high until these cells enter the distal corpus and cauda. The proportion of cells exhibiting this form of tyrosine phosphorylation is not affected by extracellular calcium or cAMP but is negatively correlated (R2 = 0.99) with their ability to acrosome-react. However, this relationship is not causative. Our findings indicate that the development of functional spermatozoa is accompanied by carefully orchestrated changes in tyrosine phosphorylation, controlled by independent regulatory mechanisms in distinct subcellular compartments of these highly specialized cells.

acrosome reaction, calcium, cAMP kinase, epididymis, kinases, sperm, sperm hyperactivation, sperm maturation, sperm motility, tyrosine phosphorylation

FOOTNOTES

1 Supported by the University of Newcastle and by the ARC Centre of Excellence in Biotechnology and Development.

2 Correspondence: FAX: 02 4921 6953; jaitken{at}mail.newcastle.edu.au

3 These authors contributed equally to this work.






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Copyright © 2006 by the Society for the Study of Reproduction.