Expression and Immunolocalization of p59c-fynTyrosine Kinase in Rat Eggs

Abstract

Fertilization overcomes meiotic arrest by triggering a series of biochemical events, resulting in activation of the egg. A small group of protein tyrosine kinases (PTKs) have been identified in eggs of invertebrates and lower vertebrates and inhibitor studies have suggested that they play a role in late events of egg activation. A recent study using the sea urchin system demonstrated that Fyn kinase was expressed in eggs and was activated within minutes of fertilization. In the present study, Western blot analysis as well as immune complex kinase assay demonstrated that p59(c-fyn) kinase was expressed in both unfertilized and fertilized rat eggs. Immunofluorescence confocal microscopy demonstrated that Fyn kinase was localized to the egg cortex but also to the polar body and the fertilizing cone which are elevated from the cortical cytoplasm of the activated egg. Surprisingly, Fyn was also found to be highly concentrated over the meiotic and mitotic spindles. To date, Fyn is the first PTK demonstrated to be present in the mammalian egg. Localization of Fyn to the egg cortex as well as the spindle microtubules indicates that this protein kinase may have multiple functions within the egg.

Proline-rich tyrosine kinase2 is involved in F-actin organization during in vitro maturation of rat oocyte

“…However, its expression and localization in oocyte is not known. Expression of Fyn, a member of Src kinase family (SFKs), is demonstrated and its activity is detected in rat eggs, which represents the first demonstration of a PTK in mammalian eggs (Talmor et al 1998). Furthermore, other members of SFKs, including Src and Yes, were detected in rat eggs (Talmor-Cohen et al 2004).…”

Role of Src homology 2 domain-mediated PTK signaling in mouse zygotic development

“…For example, while mammalian eggs express Fyn, Yes, and in some cases, Src (Talmor et al 1998, Talmor-Cohen et al 2004a), the results of two different studies indicate that these kinases are not required for the unique sperm-induced calcium oscillations (Kurokawa et al 2004a, Mehlmann & Jaffe 2005, which trigger egg activation in mammals (Carroll 2001). Instead, these calcium oscillations are triggered directly by a sperm-borne phospholipase that does not require PTK regulation (Cox et al 2002).…”

“…2A). In general, the distribution of Fyn in the mouse egg resembled with that previously reported for the rat egg (Talmor et al 1998) except that specific localization of Fyn to the meiotic spindle was not observed in the mouse oocyte under these conditions. After fertilization, Fyn remained concentrated in the egg cortex, including the region of sperm incorporation (Fig.…”

Myristoylated alanine-rich C kinase substrate, but not Ca2+/calmodulin-dependent protein kinase II, is the mediator in cortical granules exocytosis

“…Rats were killed 14 h after hCG administration. Cumulus-enclosed MI eggs were removed from the oviductal ampullae into Toyoda HEPES (TH; Ben-Yosef et al 1998) medium or into Ca 2C -and Mg 2C -free TH (TH K/K ) medium, both supplemented with 0.4% BSA (fraction V, Sigma; Talmor et al 1998). Cumulus cells were removed by a brief exposure to 400 IU/ml of hyaluronidase (Sigma).…”