MicroRNA-275 targets Ca2+-ATPase to control Notch in the mosquito gut

The yellow fever mosquito, Aedes aegypti, transmits a number of devastating human diseases such as dengue fever, yellow fever and, more recently, chikungunya fever. Female mosquitoes need vertebrate blood for egg development, and repeated cycles of blood feeding are tightly linked to pathogen transmission. The miRNA aae-miR-275 (miR-275) has previously been shown to be required for normal blood digestion in the female mosquito; however, the mechanism of miR-275 action remains unknown. Here we show, miR-275 function was inhibited in vivo by using a combination of the midgut-specific yeast transcription activator protein Gal4/upstream activating sequence system and miRNA Tough Decoy RNA technology. The endogenous level of miR-275 is highly reduced in the midgut of transgenic mosquitoes expressing miR-275 Tough Decoy post blood meal. The midgut specific reduction of miR-275 post blood meal decreased sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) mRNA levels and affected the Notch signaling pathway, resulting in a disruption of normal blood digestion and egg production. Significantly, the level of miR-275 and SERCA expression in the mosquito midgut correlates with blood digestion. These findings show blood meal induced miR-275 specifically functions in the midgut, where it may stabilize the SERCA transcript and assures blood digestive process to be accomplished normally.