Stem-loop binding protein (SLBP) is required for replication-dependent histone mRNA metabolism in mammals. Zebrafish possesses two slbps, and slbp1 is necessary for retinal neurogenesis. However, the detailed expression and function of slbp2 in zebrafish are still unknown. In this study, we first identified zebrafish slbp2 as an oocyte-specific maternal factor and then generated a maternal-zygotic slbp2F3 homozygous mutant (MZslbp2 Delta 4(-/-)) using CRISPR/Cas9. The depletion of maternal Slbp2 disrupted early nuclear cleavage, which resulted in developmental arrest at the MBT stage. The developmental defects could be rescued in slbp2transgenic MZslbp2 Delta 4(-/-) embryos. However, homozygous mutant MZslbp1 Delta 1(-/-)developed normally, indicating slbp1 is dispensable for zebrafish early embryogenesis. Through comparative proteome and transcriptome profiling between WT and MZslbp2 Delta 4(-/- )embryos, we identified many differentially expressed proteins and genes. In comparison with those in WT embryos, four replication-dependent histones, including H2a, H2b, H3, and H4, all reduced their expression, while histone variant h2afx significantly increased in MZslbp2 Delta 4(-/- )embryos at the 256-cell stage and high stage. Zebrafish Slbp2 can bind histone mRNA stem-loop in vitro, and the defects of MZslbp2 Delta 4(-/-) embryos can be partially rescued by overexpression of H2b. The current data indicate that maternal Slbp2 plays a pivotal role in the storage of replication-dependent histone mRNAs and proteins during zebrafish oogenesis.
