In Drosophila, the zinc-finger transcription factor Zelda is bound to regulatory regions of genes expressed by the zygote, and in zebrafish, the homeodomain protein Pou5f3 (a paralog of mammalian POU5F1 (OCT4) has an analogous role.
Without the function of these proteins MBT gene expression synchrony is disrupted, but particular mechanisms of coordinating the timing of gene expression are still unknown but being studied.