earticle

영어

Maternal (oocyte-derived) follistatin has a positive functional role in control of time to first cleavage of bovine embryos, subsequent development to the blastocyst stage and in blastocyst cell allocation to the trophectoderm lineage. Follistatin binds to and inhibits activity of members of the transforming growth factor superfamily, whose signals are mediated intracellularly primarily through activation of receptor associated SMADs (rSMADs) including SMAD-2/3 (activin, TGF-b) and SMAD-1/5/8 (BMPs). We hypothesized that the positive actions of follistatin on early embryogenesis may be mediated via inhibition of ligand induced rSMAD signaling. To address this hypothesis, we determined the temporal expression and effects on bovine early embryogenesis of siRNA mediated knockdown of SMAD-4. SMAD-4 is a common component of above signaling pathways which complexes with respective rSMADs. SMAD-4 mRNA in early embryos is maternally derived and its abundance is temporally regulated during early embryogenesis. SMAD-4 siRNA injection at the zygote stage also significantly reduced proportion of embryos cleaving early and proportion of embryos developing to the 8~16 cell and blastocyst stages. Furthermore, SMAD-4 siRNA injection at the zygote stage had no effect on abundance of mRNA for the trophectoderm cell marker CDX2 and inner cell mass cell marker Nanog in bovine blastocysts. Results suggest a functional role for maternal (oocyte-derived) SMAD-4 in bovine early embryonic development. However, the phenotype of SMAD-4 depleted embryos is distinct from that observed in response to follistatin ablation or replacement.