Identification and characterization of a mosquito-specific eggshell organizing factor in Aedes aegypti mosquitoes

Abstract

Mosquito-borne diseases are responsible for several million human deaths annually around the world. One approach to controlling mosquito populations is to disrupt molecular processes or antagonize novel metabolic targets required for the production of viable eggs. To this end, we focused our efforts on identifying proteins required for completion of embryonic development that are mosquito selective and represent potential targets for vector control. We performed bioinformatic analyses to identify putative protein-coding sequences that are specific to mosquito genomes. Systematic RNA interference (RNAi) screening of 40 mosquito-specific genes was performed by injecting double-stranded RNA (dsRNA) into female Aedes aegypti mosquitoes. This experimental approach led to the identification of eggshell organizing factor 1 (EOF1, AAEL012336), which plays an essential role in the formation and melanization of the eggshell. Eggs deposited by EOF1-deficient mosquitoes have nonmelanized fragile eggshells, and all embryos are nonviable. Scanning electron microscopy (SEM) analysis identified that exochorionic eggshell structures are strongly affected in EOF1-deficient mosquitoes. EOF1 is a potential novel target, to our knowledge, for exploring the identification and development of mosquito-selective and biosafe small-molecule inhibitors.

Recombinant Expression and Potential Autocatalysis of Aedes aegypti Trypsin-like Serine Proteases (AaSPII and AaSPIV)

“…aegypti proteases have shown that only three have an effect on mosquito fecundity: AaLT, AaSPVI, and AaSPVII. 22 While mRNA knockdown of each individual protease resulted in a decrease in the amount of eggs laid by the mosquito, knockdown of all three of these proteases at once did not have an overall additive decrease as expected. 22 This suggests that other Ae.…”

“…20,21 With no effective treatment for Dengue, Zika, or Chikungunya infection, no vaccines available to combat these viruses, and a relentless increase in vector-borne disease cases reported globally, there is a vital need to control the disease through the only available method: vector control. 3,15,22,23…”

“…Previous research confirms that reducing the percentage of blood in the female mosquito blood meal significantly decreases the amount of viable eggs produced. 22 By effectively inhibiting the digestion of blood meal proteins with synthetic peptide analog inhibitors, the mosquito would be unable to render nutrients from the blood necessary for egg development, reducing the population of future mosquito generations.…”

“…aegypti mosquitoes occurs in a biphasic manner; midgut trypsin-like activity increases during the early phase of digestion, 0 to 6 h post blood meal (PBM), and the late phase of digestion shows a more dramatic increase 12-18 h PBM. 22,43 Three serine proteases showing the highest expression levels in female Ae.…”

“…aegypti genome and subsequent bioinformatics analyses identified another abundant protease, AaSPVII, in addition to other midgut proteases. 22,35,45 Of the hundreds of serine protease-like genes in the Ae. aegypti genome, 66 were identified as potential trypsins and just nine of these were found to be expressed in the midgut.…”