PP2Cδ ( Ppm1d , WIP1), an endogenous inhibitor of p38 MAPK, is regulated along With Trp53 and Cdkn2a following p38 MAPK inhibition during mouse preimplantation development

Preimplantation embryos utilize mitogen‐activated protein kinase signaling (MAPK) pathways to relay signals from the external environment to prepare appropriate responses and adaptations to a changing milieu. It is therefore important to investigate how MAPK pathways are regulated during preimplantation development. This study was conducted to investigate whether PP2Cδ ( Ppm1d , WIP1) is expressed during mouse preimplantation development and to determine the influences of p38 MAPK inhibition on expression of Trp53 (p53), Ppm1d , (WIP1), and Cdkn2a (p16) during mouse preimplantation development. Our results indicate that Trp53 , Ppm1d , and Cdkn2a mRNAs and TRP53 and PP2Cδ proteins are expressed throughout mouse preimplantation development. Treatment of 2‐cell embryos with SB220025 (potent inhibitor of p38 MAPK α/β/MAPK 14/11) significantly increased Trp53 , Ppm1d and Cdkn2a and Mapk14 mRNA levels at 12 and 24 hr. Treatment of 8‐cell embryos with SB220025 for 12 hr increased Trp53 , Ppm1d , and Cdkn2a mRNA levels, but not Mapk14 mRNA levels. Treatment of 8‐cell embryos for 24 hr increased Trp53 , and Ppm1d mRNA levels, but decreased Cdkn2a and Mapk14 mRNA levels. Therefore, blockade of p38 MAPK activity is associated with embryo stage specific influences on Trp53 , Ppm1d , Cdkn2a , and Mapk14 expression during mouse preimplantation development. These results define downstream targets of p38 MAPK during preimplantation development and indicate that the p38 MAPK pathway regulates Trp53 , Ppm1d , and Cdkn2a expression. This study increases our understanding of the mechanisms controlling preimplantation development and of the interactions between preimplantation embryos and their culture environments. Mol. Reprod. Dev. 74: 821–834, 2007. © 2007 Wiley‐Liss, Inc.