Developmental Expression of Src-Related Tyrosine Kinases in the Mouse Testis

Abstract

An increase in protein tyrosine phosphorylation occurs during sperm capacitation in numerous species. The involvement of Src-related tyrosine kinases in this phenomenon has been demonstrated using different inhibitors specifically targeting this family of enzymes. In mammals, this group of nonreceptor tyrosine kinases is made up of 8 members with similar SRC homology domain 3 (SH3) and SH2 domains. Although some members of this group of enzymes can compensate for one another, showing some redundancy, each is unique and may perform specific functions during male germ cell development. To further characterize the importance of Src-related tyrosine kinases in the events leading to proper sperm formation, and because no inhibitor affecting a single gene product exists, expression of Src, Yes1, Fyn, Lyn, Lck, Hck, Blk, and Fgr was assessed by real-time polymerase chain reaction in developing mouse testes and in enriched populations of mouse spermatogenic cells, revealing distinct expression profiles for each kinase during testis development and in isolated male germ cells. Immunolocalization of SRC, LYN, and HCK in adult mouse testes as well as in mature spermatozoa further confirmed differential localization of these kinases during spermatogenesis. Although mRNA levels of these latter kinases were higher in spermatogonia and spermatocytes than in spermatids, protein levels were highest in spermatids, suggesting delayed transcript translation. Taken together, these results clearly show an uneven expression of each kinase in different spermatogenic cells, indicating that each member may play a different role during spermatogenesis, in addition to highlighting the complexity of Src-related kinase expression regulation in male germ cells. Furthermore, differential localization of these tyrosine kinases in mature spermatozoa also suggests a specific role for each member in sperm function and integrity.

The association between CDC42 and caveolin-1 is involved in the regulation of capacitation and acrosome reaction of guinea pig and mouse sperm

“…Several members of the SFK such as cYes, c-SSC, Fyn, and Lyn have been involved in sperm capacitation (Leclerc & Goupil 2002, Baker et al 2006, Kierszenbaum et al 2009, Goupil et al 2011. SU6656 has been identified as an inhibitor closely related to these kinases; in spite of this, our results do not clarify which kinase is related to CAV1 phosphorylation.…”

The Blood-Testis Barrier and Its Implications for Male Contraception

“…8). In the testis, both c-Src Goupil et al, 2011) and c-Yes (Xiao et al, 2011) are localized to the BTB and the apical ES in the seminiferous epithelium of adult rat testes. Although c-Yes and c-Src are two closely related members of the Src kinase family and they share redundancy in their signaling functions, they have different cellular functions in multiple epithelia (Summy et al, 2003;Sato et al, 2009).…”

“…These findings thus clearly illustrate differences in c-Src and c-Yes signaling functions. Other Src kinases, such as Hck (and its truncated form) and Lyn, are also detected in the testis based on immunohistochemistry experiments, and truncated Hck was found to localize predominantly to the apical ES (Bordeleau and Leclerc, 2008;Goupil et al, 2011); however, their role at the BTB remains unexplored.…”

Role of FYN Kinase in Spermatogenesis: Defects Characteristic of Fyn-Null Sperm in Mice1

“…Previous studies have provided evidence that the Src gene family kinases play a role in several aspects of testis and sperm function [1,3,[8][9][10][11]28]. However, the use of chemical inhibitors that lack absolute specificity and the absence of detailed fertility analysis of mouse models in which Src gene family PTKs have been knocked out have limited the interpretations of the functional studies to date.…”

“…The Src gene family kinases have been associated with multiple aspects of sperm and testis function [1][2][3], and an understanding of their specific actions in the testis and in mature sperm may present unique opportunities for contraceptive development and provide insight into the cause of human male infertility. The Src gene family kinases exhibit distinct expression profiles in the testis, and the four (Src, Yes, Fyn, and Hck) gene family members have been implicated in various aspects of testis or sperm function.…”