Nuclear factor-kappa-B-inhibitor alpha (NFKBIA) is a developmental marker of NF-kappa B/p65 activation during in vitro oocyte maturation and early embryogenesis

METHODS AND RESULTS: We found a dynamic correlation between NFKBIA transcript, expression of I kappa B alpha-protein and activation of NF-kappa B/p65 in bovine oocyte and embryo. During the transition from immature to in vitro matured bovine oocyte, we observed a decrease in maternal NFKBIA mRNA and a parallel increase of the I kappa B alpha-protein (both P < 0.05). In the embryo, NFKBIA neo-synthesis is activated as a consequence of embryo genome activation (EGA), and IkBa decreases. NF-kappa B/p65-binding activity was detectable at low levels in immature oocyte, disappeared in dormant metaphase II oocyte and was strong in the embryo, during embryonic NFKBIA synthesis. The level of NF-kappa B/p65 DNA binding correlates with the timing of meiotic silencing during bovine oocyte maturation and embryonic transcription reprogramming.

BACKGROUND: The oocyte-to-embryo transition (OET) requires a co-ordinated transcriptional programme acting through evolutionarily conserved events, and transcription factors (TFs) are known to control these processes. Here, we focus on nuclear factor (NF)-kappa B, a TF involved in several cellular processes, studying NF kappa B-inhibitor (NFKBIA) mRNA and its protein product, I kappa B alpha, during OET. NFKBIA and IkBa are part of a regulatory loop, as IkBa is the major down-regulator of NF-kappa B activation while NFKBIA transcription is activated by NF-kappa B.