Yue, H.M., Li, Z., Wu, N., Liu, Z., Wang, Y., and Gui, J.F. (2013) Oocyte-Specific H2A Variant H2af1o Is Required for Cell Synchrony Before Mid-Blastula Transition in Early Zebrafish Embryos. Biology of reproduction. 89(4):82.
Oocyte-specific histone variants have been expected to play significant roles in early embryonic development, but the exact
evidence and the biological function have remained unclear. Here, we present evidence that H2af1o, an oocyte-specific H2A
variant, is required for cell synchrony before mid-blastula transition in early zebrafish embryos. The H2A variant is oocyte-specific,
peaks in mature eggs and is supplied to early embryos. We constructed a series of deletion plasmids of the zebrafish h2af1o tagged with EGFP, and determined the main key function regions including nuclear localization signal of N-terminal 25 amino
acids and nucleosome binding region of 110-122 amino acid sequence in the C-terminus by microinjecting them into one-cell
stage zebrafish embryos. In comparison with ubiquitous H2A.X, the H2af1o was revealed to confer a more open structure than
canonical H2A in the nucleosomes. Furthermore, we conducted the h2af1o-specific morpholino knockdown analysis in early embryos of zebrafish, and revealed its biological function for maintaining
cell synchrony division because the H2af1o deficiency disturbed cell synchrony in early cleavages before mid-blastula transition.
Therefore, our current findings provided the first case to understand the biological function of maternal oocyte-specific
histone variants in vertebrates.