PROTEIN-PHOSPHORYLATION IS ESSENTIAL FOR FORMATION OF MALE PRONUCLEUSIN BOVINE OOCYTES

This study examined the association between the morphological and prot ein phosphorylation events following sperm penetration of in vitro mat ured and in vitro fertilized bovine oocytes. Oocytes were labeled with [P-32]-orthophosphate at 3 hr intervals from 3 to 18 hr of following insemination. The phosphorylation of protein complexes of 23 kDa and 1 8 kDa specifically increased with the formation of male and female pro nuclei. In addition, oocytes were treated with 6-Dimethylaminopurine ( 6-DMAP) or Okadaic acid (OA) at 0, 3, 6, and 9 hr respectively followi ng insemination. Although the formation of female pronucleus was not a ffected by 6-DMAP, the male pronuclear formation was completely inhibi ted by the presence of 6-DMAP at 0 and 3 hr of post insemination. The formation of both pronuclei was inhibited by the presence of OA at any time following insemination. These results suggest that the male pron uclear formation is associated with protein phosphorylation and that t he formation of the male and the female pronuclei may involve differen t factors in bovine zygotes since they respond differently to the kina se modulations. Mol. Reprod. Dev. 52:43-49, 1999. (C) 1999 Wiley-Liss, Inc.