The northern house mosquito Culex pipiens, a major disease vector of West Nile virus across the globe, enter adult diapause to survive inimical conditions during winter. The extended lifespan of diapause-invoked Cx. pipiens is one of the hallmarks of diapause phenotypes. Post-translational modifications of histone proteins influence gene expression and have been associated with aging in many multicellular organisms. To expand our understanding of lifespan extension in diapausing mosquitoes and its connection to epigenetic modifications, we performed Western blot studies using antibodies against different histone methylations with fat body and ovary samples from Cx. pipiens. H3K27 methylation is known to play an important role in the developmental process through chromosomal activation and inhibition in many eukaryotic organisms. The predominant regulatory mechanism involves the polycomb repressive complex 2. Interestingly, we discovered that the genes related to this complex were the target genes of FOXO through our ChIP-seq experiment. Overall, these results show that the level of histone methylation does not change in the ovaries at the onset of diapause in this mosquito, but specifically, the level of H3K27me2 is significantly reduced more than twofold in the fat body. In the future, we intend to conduct a study on the mechanisms regulating H3K27me2 in the fat body and if it affects the extended lifespan in diapausing mosquitoes.
