HNF4 paralogue gene expression and function in the kissing bug Rhodnius prolixus

Abstract

HNF4 is a transcription factor and member of the nuclear receptor superfamily, proteins that play important roles in development and metabolism. HNF4 is a key gene in the adaptation to fasting and regulates many genes involved in lipid oxidation and mobilization. Mammalian genomes contain two paralogues named HNF4 alpha and HNF4 gamma, but most insect genomes have only one HNF4 gene. After the publication of the Rhodnius prolixus genome, we noticed there were two paralogous HNF4 genes known as RpHNF4.1 and RpHNF4.2. Currently, little is known about HNF4 function in the kissing bug R. prolixus, so study of HNF4 paralogues may provide unique insight into the metabolism and physiology of this important vector for Chagas Disease. A qPCR analysis reveled different patterns of expression of these two genes in different R. prolixus organs, with RpHNF4.1 expressed mainly in ovaries while RpHNF4.2 is the main form expressed in fat body, midgut and flight muscle, suggesting they may have different functions. Drosophila melanogaster is a useful insect model organism with genetic tools that can be used to test the conserved functions of the HNF4 paralogues from R. prolixus. Because R. prolixus has a long life cycle and few genetic tools, we are constructing D. melanogaster transgenic flies to conditionally express each gene in wild‐type and dHNF4 null mutant backgrounds. Loss of dHNF4 in these flies produces adult lethality and these animals acumulate triacylglycerol in the fat body and have low expression of genes involved in the beta oxidation pathway as larvae. Using the GAL4‐UAS system, we aim to generate flies expressing only RpHNF4.1 or RpHNF4.2 without the interference of dHNF4. With these constructs, we will be able to evaluate alterations and possible rescue of the lifespan and lipid metabolism pathway independently for each R. prolixus HNF4 gene. This data may shed some light in their individual physiological roles and suggest new lines of investigation on the lipid metabolism of the Chagas desease vector. Ultimately, a better understanding of conserved features of HNF4 paralogues may provide new molecular targets for obesity treatment in other organisms.Support or Funding InformationThe first author is a Fulbright Scholar at Binghamton University. Special thanks to the Fulbright Comission Brazil. CAPES, CNPq and FAPERJ.