Research

Our research aims to define the integrative neuroendocrine control of reproductive structures and associated visceral tissues (eg. digestive, cardiac) in the agricultural pest Locusta  migratoria and in the medically-important vector of Chagas’ disease, Rhodnius prolixus; and to define the integrative control of ecdysis behaviour (shedding of the exoskeleton) through the coordinated action of neuropeptides on CNS and associated peripheral systems (cardiac, digestive, skeletal muscle) in R. prolixus.

Our scientific approach is holistic and incorporates multi-facetted aspects from gene to behaviour.  We define the neural substrates and circuits (including their neuroactive chemicals and receptors) used in the integrative control of these behaviours using a variety of techniques including molecular biology, pharmacology, neurophysiology, physiological assays, peptide isolation, neural mapping, and immunohistochemistry. 

Novelty and expected significance: Our long term goal is to study how cells communicate with one another in order to produce an appropriate physiological and behavioral output. We identify and define the interactions between the diverse neurochemicals which are used in our model systems, and also look at interactions / coordination of organ systems. The importance of research into insects lies increasingly in the testing and demonstration of universal principles of neural organization and functioning, while identifying unique features for target of novel pest control strategies. For example, just like the pharmaceutical industry, the agrochemical industry is targeting neuroactive chemicals and GPCRs for novel pest control strategies due to the ever increasing resistance to the current generation of pesticides.  The future is hopeful, especially for neuropeptides, where the intrinsic problems associated with their use have been overcome. This need for control is particularly relevant for our model insects, L. migratoria and R. prolixus.  Locusts are agricultural pests, eating or destroying crops and affecting over 20% of the earth’s land and more than 65 of the world’s poorest countries.  Their swarms lead to devastating consequences in many developing countries.  The medically-important insect, R. prolixus, is the vector of human Chagas disease, and whilst once considered to be confined to the Americas, Chagas disease now occurs throughout the World due to human migration and blood transfusions.  For example, it is estimated that 300,000 people are infected in the USA, 50,000 in Spain and 2,000 in Canada.  Therefore, this research has the potential to discover lead compounds that can be developed into bio-pesticides in the future.

Research Excellence Award 2006/2007:  http://www.utm.utoronto.ca/vp-research/research-campus/u-t-mississauga-excellence-awards/desmond-morton-research-excellence-award

Teaching Excellence Award 2004/2004: http://www.utm.utoronto.ca/vp-research/teaching-excellence-award-faculty

Examples of Significant Contributions to Research; Students and Post-docs indicated in Bold.  For more complete list see https://www.researchgate.net/profile/Angela_Lange2/contributions and https://loop.frontiersin.org/people/20990/publications

 

  1. Mesquita RD , …Lange AB…. et al.(2015). Genome of Rhodnius prolixus, an insect vector of Chagas disease, reveals unique adaptations to hematophagy and parasite infection. Proceedings of the National Academy of Sciences. 112(48): 14936-41. This publication came about from funding from NIH in response to a White paper written by a consortium of Rhodnius researchers. As a member of this consortium I was active in the consortium meetings, provided insects for determining the best colony to use for the sequencing, provided libraries and transcriptomes, disseminated research in progress, and participated in annotation. This genome publication has contributed to significant advances in biomedical and biological research in Rhodnius and the consortium has provided a wonderful vehicle for collaborative research and research performed in my lab.

 

  1. Lee, D.H., Vanden Broeck, J. and Lange, A.B. 2013. Identification and expression of the CCAP receptor in the Chagas’ disease vector, Rhodnius prolixus, and its involvement in cardiac control. PLoS ONE 8(7): e68897.  Rhodnius prolixus is the vector of Chagas’ disease, by virtue of transmitting the parasite Trypanosoma cruzi. Understanding the physiology of the disease vector is an important step in developing control measures. Crustacean cardioactive peptide (CCAP) is an important neuropeptide in insects since it has multiple physiological roles such as controlling heart rate and modulating ecdysis behaviour. In this study, we cloned the cDNA sequence of the CCAP receptor (RhoprCCAPR) from 5th instar R. prolixus and found it to be a G-protein coupled receptor (GPCR). A functional receptor expression assay confirms that the RhoprCCAPR is activated by CCAP but not by other peptides. The involvement of CCAP in controlling heartbeat frequency was studied in vivo and in vitro by utilizing RNA interference. In vivo, the basal heartbeat frequency is decreased by 31% in bugs treated with dsCCAPR. Knocking down the receptor in dsCCAPR-treated bugs also resulted in loss of function of applied CCAP in vitro. The significance of this work is that this is the first report of a GPCR knock-down in R. prolixus and the first report showing that a reduction in CCAPR transcript levels leads to a reduction in cardiac output in any insect. It also proves we have the molecular tools to precisely interfere with peptide signaling pathways using double stranded RNA (dsRNA) and the susceptibility of R. prolixus to RNA interference (RNAi).

 

  1. Lee, D.H., Orchard, I. and Lange, A.B. 2013.  Evidence for a conserved CCAP-signaling pathway controlling ecdysis in a hemimetabolous insect, Rhodnius prolixus.  Frontiers in Neuroendocrine Science (ref).  A vital feature in the success of Ecdysozoa is their ability to shed their exoskeleton (a process called ecdysis) allowing them to grow or change their morphology. The behaviour of ecdysis is very well studied in holometabolous insects, such as Drosophila melanogaster and Manduca sexta, and these behaviours are orchestrated by the actions of neuropeptides. Little is known about the control of ecdysis in hemimetabolous insects. Here, we report that CCAP is an essential neuropeptide for successful ecdysis in the hemimetabolous insect, Rhodnius prolixus. The critical importance of the CCAP signaling pathway was demonstrated by knockdown (as determined by qPCR and immunohistochemistry) of the CCAP and CCAPR transcripts utilizing dsRNA. This technique of RNAi reduced the staining intensity of CCAP-containing neurons suggesting a reduction in the presence of the peptide in the central nervous system (CNS), and knocked down the transcript levels by up to 83%, with lethal consequences to the insect. Insects with these transcripts knocked down had very high mortality (up to 84%), typically at the expected time of ecdysis, or had a delay in the time to ecdysis. This is the first report of the susceptibility of R. prolixus to dsRNA knockdown of both neuropeptide and receptor transcripts, and the data clearly demonstrates for the first time the conserved nature of the CCAP signaling pathway in ecdysis between holometabolous and hemimetabolous insects.  This paper, which also describes in detail the timing of and behaviours associate with ecdysis now paves the way for identifying all of the neuropeptide cascade that R. prolixus uses in controlling this essential process of ecdysis.