Suppression of the H3K27me3 demethylase disrupts diapause formation in mosquito Culex pipiens

Diapause (D) is a hormonally controlled alternative developmental pathway that allows mosquitoes to survive harsh winter conditions. Key characteristics of mosquito diapause include elevated lipid storage, enhanced stress and cold endurance, and extended longevity. These phenotypic changes are often associated with dynamic alterations in the transcriptome and epigenome. In our previous study, we identified significantly lower H3K27me2 levels in the fat body (FB) of diapausing Culex pipiens. However, the specific roles of the repressive H3K27 methylation marks in mosquito diapause have not been investigated. In the present study, we employed the effective histone lysine demethylase inhibitor GSK-J4 to assess the functions of H3K27me3 levels in the fat body on diapause initiation and phenotypes in Cx. pipiens. Results from solid-state NMR (ssNMR), Fourier-transform infrared spectroscopy (FTIR), and biochemical assays suggest that elevated H3K27me3 levels via GSK-J4 inhibition led to disrupted accumulation of lipids and glycogen in diapausing mosquitoes. GSK-J4 treatment also increased the mortality rate, resulting in lower survivability in treated mosquitoes. Together, these findings propose a crucial role for H3K27me3 in diapause formation, particularly related to energy metabolism. Our results provide a potential target for novel vector control strategies for this species.