Buc Maintains Maternal RNA Stability and Embryogenesis in Zebrafish.

The maternal-to-zygotic transition (MZT) is a fundamental process in vertebrate embryogenesis, involving the clearance of maternal mRNA and activation of the zygotic genome. Orchestration of maternal mRNA stability ensures early embryogenesis. Recently, some germ plasm (GP) factors have been demonstrated to regulate the stability of maternal mRNA. Bucky ball (Buc) functions as a zebrafish GP organizer. However, it remains unclear whether Buc also protects maternal mRNAs from widespread decay in early embryos. Here, we report that overexpression of buc results in delayed maternal mRNA degradation and a concomitant delay in embryonic development, whereas buc knockout leads to accelerated maternal mRNA degradation and severe developmental defects, suggesting that both gain and loss of buc perturb early developmental programs. Mechanistically, this regulatory mechanism of Buc on maternal mRNA is mediated through the expression of RNA-binding protein Igf2bp3. Together, our findings suggest that the GP organizer Buc may stabilize maternal mRNAs in coordination with Igf2bp3, thereby contributing to the maintenance of maternal mRNA required for proper embryonic development during the MZT. This study expands the functional scope of Buc beyond GP assembly and reveals its critical role in safeguarding maternal mRNA integrity to ensure proper embryo development.