Juvenile hormone induced histone deacetylase 3 suppresses apoptosis to maintain larval midgut in the yellow fever mosquito, Aedes aegypti

The yellow fever mosquito, Aedes aegypti is distributed worldwide and transmits viruses that cause many diseases, including dengue, yellow fever, chikungunya and zika. Epigenetic modifications such as acetylation of histones regulated by histone acetyltransferases (HATs) and histone deacetylases (HDACs) control insect development. Currently, one of the HATs, the Creb-binding protein (CBP) is known to regulate the metamorphosis of Ae. aegypti. However, no reported roles of HDACs are known in Ae. aegypti. Hence, in this study, we identified AaHDAC3 and determined its role in Ae. aegypti larval development using RNA interference (RNAi). To identify the targets of AaHDAC3, we knockdown AaHDAC3 in Ae. aegypti derived Aag-2 cells and performed RNA sequencing. After quality control analysis, reads were mapped back to Ae. aegypti Liverpool transcriptome. Then differential gene expression analysis of RNA sequencing data identified 169 genes that are differentially expressed (P-value 2-fold change) between the cells treated with double-stranded RNA targeting AaHDAC3 and control cells treated with dsmalE (dsRNA targeting maltose-binding protein). Among differentially expressed genes, 103 genes were upregulated, and 66 genes were downregulated in AaHDAC3 knockdown cells. Gene enrichment analysis revealed that genes involved in apoptosis, postembryonic development, DNA binding transcription factors, etc., are significantly enriched in upregulated genes group of AaHDAC3 knockdown samples. Notably, AaHDAC3 knockdown induced the apoptosis-triggering genes that promoted apoptosis of midgut cells, reduced the larval midgut size and caused Ae. aegypti larval death. These results demonstrate that HDAC3 plays a key in maintaining the larval midgut and larval stage in Ae. aegypti.