A class I histone deacetylase HDA-2 is essential for embryonic development and size regulation of fertilized eggs in Caenorhabditis elegans

Background: Caenorhabditis elegans encodes three class I histone deacetylases (HDACs), HDA-1, HDA-2, and HDA-3. Although HDA-1 is known to be involved in embryogenesis, the regulatory roles of HDA-2 and HDA-3 in embryonic development remain unexplored.

Objective: To elucidate the functional roles of the three class I HDACs in C. elegans embryonic development.

Methods: The roles of Class I HDACs, HDA-1, HDA-2, and HDA-3 in Caenorhabditis elegans during embryogenesis were investigated through the analysis of embryonic lethality via gene knockdown or deletion mutants. Additionally, the size of these knockdown and mutant eggs was observed using a differential interference contrast microscope. Finally, expression pattern and tissue-specific role of hda-2 and transcriptome of the hda-2 mutant were analyzed.

Results: Here, we report that HDA-1 and HDA-2, but not HDA-3, play essential roles in Caenorhabditis elegans embryonic development. Our observations of the fertilized egg size variance demonstrated that HDA-2 is involved in regulating the size of fertilized eggs. Combined analysis of expression patterns and sheath cell-specific rescue experiments indicated that the transgenerational role of HDA-2 is involved in the viability of embryonic development and fertilized egg size regulation. Furthermore, transcriptome analysis of hda-2 mutant embryos implies that HDA-2 is involved in epigenetic regulation of embryonic biological processes by downregulating and upregulating the gene expression.

Conclusion: Our finding suggests that HDA-2 regulates the embryonic development in Caenorhabditis elegans by controling a specific subset of genes, and this function might be mediated by transgenerational epigenetic effect.