Functions of Fyn kinase in the completion of meiosis in mouse oocytes

Abstract

Oocyte maturation invokes complex signaling pathways to achieve cytoplasmic and nuclear competencies for fertilization and development. The Src-family kinases FYN, YES and SRC are expressed in mammalian oocytes but their function during oocyte maturation remains an open question. Using chemical inhibitor, siRNA knockdown, and gene deletion strategies the function of Src-family kinases was evaluated in mouse oocytes during maturation under in vivo and in vitro conditions. Suppression of Src-family as a group with SKI606 greatly reduced meiotic cell cycle progression to metaphase-II. Knockdown of FYN kinase expression after injection of FYN siRNA resulted in an approximately 50% reduction in progression to metaphase-II similar to what was observed in oocytes isolated from FYN (−/−) mice matured in vitro. Meiotic cell cycle impairment due to a Fyn kinase deficiency was also evident during oocyte maturation in vivo since ovulated cumulus oocyte complexes collected from FYN (−/−) mice included immature metaphase-I oocytes (18%). Commonalities in meiotic spindle and chromosome alignment defects under these experimental conditions demonstrate a significant role for Fyn kinase activity in meiotic maturation.

Dynamics of protein phosphorylation during meiotic maturation

“…Our recent studies have focused on the role of SFKs during oocyte maturation and fertilization [10,11,14]. The present data reinforce a role for Fyn kinase in what we suggest is an example of cortical maturation.…”

“…However, Fyn (-/-) oocytes lacked pTyr spindle pole labeling at MI or MII. This distinct spatial change in spindle pole foci helps explain our previous data showing spindle and chromosome dysfunction during meiosis of Fyn (-/-) oocytes [10,14]. Collectively, these findings implicate a role for Fyn kinase in establishing spindle pole integrity and chromosome segregation at meiosis I and II.…”

“…Fyn knock-out oocytes fail to increase cortical phosphorylation of pTyr proteins Our studies of SFKs during meiotic maturation and fertilization have demonstrated an essential function for SFKs for proper organization of chromosomes and spindles [10,11,14]. Of the nine SFKs produced in mammalian cells, FYN kinase is expressed at very high levels in oocytes.…”

“…While ser/thr kinases are well known to drive the meiotic cell cycle, only recently has it become apparent that tyrosine kinases are also essential components in the process of oocyte maturation and early development in mammals. For example, Src-family kinases (SFKs) appear to mediate meiotic spindle and chromatin modifications in rodent oocytes [10][11][12][13][14]. Until the interplay between discrete protein kinase signaling pathways can be resolved in mammalian oocytes, the role of these factors in determining the quality of oocyte nuclear and cytoplasmic maturation will remain unclear.…”

Phospho-Signaling at Oocyte Maturation and Fertilization: Set Up for Embryogenesis and Beyond Part I. Protein Kinases

“…Further, knockdown of FYN kinase by siRNA resulted in an approximately 50% reduction in progression to metaphase II similar to what was observed in oocytes isolated from Fyn-knockout mice matured in vitro. These results clearly demonstrate that involvement of Fyn in oocyte and egg functions vary among species Kierszenbaum et al 2009;Kinsey 1995;Kinsey 1996;Kinsey and Shen 2000;Kinsey et al 2003;Levi et al 2010;Luo et al 2009;McGinnis et al 2009 Sette et al 2002;Sharma and Kinsey 2006;Sharma and Kinsey 2008;Steele et al 1990;Talmor et al 1998;Talmor-Cohen et al 2004b;Wu and Kinsey 2000;Wu and Kinsey 2002;Wu and Kinsey 2004).…”