Histone variants contribute to the structural organization of chromatin and regulation of genome functions through their deposition into the nucleosome. The histone variant H2A.Z, one of the H2A variants, is evolutionarily conserved and is suggested to be involved in various biological phenomena, including post- embryonic development and tumorigenesis. However, since H2A.Z knockout vertebrates show embryonic lethality, the function of H2A.Z in post-embryonic development remains unclear. In this study, we investigated the roles of H2A.Z in post-embryonic development with C. elegans. To avoid the effect of a load of maternal H2A.Z gene transcripts, we attempted to use the auxin-inducible degron 2 (AID2) technology (Yesbolatova et al., 2020). We introduced GFP and degron tags into the locus of
htz-1 (H2A.Z gene of C. elegans) using the CRISPR/Cas9 system and established animals expressing endogenous GFP::degron::HTZ-1 together with the AtTIR1(F79G) mutant. The treatment of the 5-Ph-IAA ligand for AtTIR1(F79G) induced the depletion of GFP::degron::HTZ-1 within two hours, allowing us to knockdown H2A.Z in stage- and cell-specific manners. The depletion of H2A.Z at the L1 larval stage results in the early larval arrest before or at the L2 stage. Also, we found that H2A.Z knockdown at the late L2 larval stage caused sterility. These results suggested that H2A.Z has essential functions during post-embryonic development at multiple developmental stages. Then, to reveal the cause of their sterility, we characterized the sterile animals by staining DNA with DAPI. Microscopy analysis revealed morphological abnormalities of sterile animals, including germline masculinization and endomitotic oocytes. These observations suggest that H2A.Z has essential roles in the germline sex determination and proper cell function of germ cells after the L2 larval stage. It is expected that the conditional H2A.Z knockdown animals contribute to further analyses of the stage- and tissue-specific roles of H2A.Z. Reference: Yesbolatova, A. et al. The auxin-inducible degron 2 technology provides sharp degradation control in yeast, mammalian cells, and mice. Nat. Commun. 11, (2020).