The insulin/insulin growth factor signaling (IIS) cascade is one of the most important signaling pathways in insects. IIS in insects regulate everything from development and growth during the immature stages, to reproduction and longevity in adult insects, to metabolism and innate immunity during all stages. While insects typically encode multiple insulin-like peptides (ILPs), these hormones appear to largely activate the IIS cascade via a single insulin receptor. This raises a fundamental question as to why multiple ILPs are necessary. They may be redundant to ensure that mutations in this critical signaling pathway are compensated for. They may act in concert to fine tune the physiologies regulated by this cascade. Or they may independently control distinct physiological processes. To explore these possibilities, we will knock-out individual ILPs in the mosquito Aedes aegypti using the CRISPR/Cas9 system. Ae. aegypti encodes eight different ILPs and we will knock-out at least three of the most intriguing ones; 1) AaegILP2, an ortholog of Drosophila DILP2, which has been implicated in regulating lifespan, reproduction, and development, 2) AaegILP6, the only putative insulin growth factor identified in mosquitoes to date, and 3) AaegILP3, which has been shown through peptide injections to control metabolism and reproduction. For these three AaegILP knock-outs lines, and any others that time and resources allow for, we will conduct expression assays in various tissues, various developmental periods and following various physiological events. We will also assess the impact of the individual AaegILP knock-outs on the following physiologies: growth and development, lifespan, metabolism, lifetime fecundity, and innate immunity. By the end of this project we will have elucidated the basic biological roles of three or more AaegILPs, broadening our understanding of key factors regulating vectorial capacity in this important arboviral vector.
Insects possess multiple insulin-like peptides, but have only a single insulin receptor that these peptides can bind to. Yet, these insulin-like peptides are still capable of controlling numerous aspects of the insect's life including lifespan, reproduction, metabolism, growth and immunity. This work will disrupt the production of individual insulin-like peptides in the yellow fever mosquito Aedes aegypti to determine how individual peptides control these very different life history events in this important vector of human pathogens.
