Research

Our group uses Drosophila and its powerful genetics on three main axes of research focusing on:

  1. Drosophila immunity
  2. Drosophila-Spiroplasma interactions: a model of endosymbiosis
  3. Science, Society and Narcissism

1) Drosophila innate immunity

Insects possess efficient mechanisms for detecting and neutralizing microbial infections. The application of Drosophila genetics to deciphering these mechanisms has generated insights into insect immunity and uncovered similarities with mammalian innate immune responses. Our research focuses on understanding mechanisms of microbial infection and corresponding host defense responses in Drosophila using genetic and genomic approaches. Our group employs genetic screens to identify novel factors regulating the immune response of Drosophila. These studies extend our understanding of how the Toll and ImdNF-kB pathways activate antimicrobial defense, as well as how the host recognizes and distinguishes between different microbial pathogens. We are also analyzing the strategies used by entomopathogenic bacteria to subvert the Drosophila innate immune system and have a long-standing interest in the gut immune response.

Figure 1. Adult fly injected with GFP expressing bacteria. This mode of infection triggers a systemic immune response consisting of the production of antimicrobial peptides by the fat body, phagocytosis by blood cells and melanization at the site of injury.
Figure 1. Adult fly injected with GFP expressing bacteria. This mode of infection triggers a systemic immune response consisting of the production of antimicrobial peptides by the fat body, phagocytosis by blood cells and melanization at the site of injury.

Recent references

Chakrabarti S, Dudzic JP, Li X, Collas EJ, Boquete JP, Lemaitre B. (2016) Remote Control of Intestinal Stem Cell Activity by Haemocytes in Drosophila. PLoS Genet. 27;12(5):e1006089.

Neyen C, Runchel C, Schüpfer F, Meier P, Lemaitre B. (2016) The regulatory isoform rPGRP-LC induces immune resolution via endosomal degradation of receptors. Nat Immunol. 17(10):1150-8. doi: 10.1038/ni.3536.

Iatsenko I, Kondo S, Mengin-Lecreulx D, Lemaitre B. (2016) PGRP-SD, an Extracellular Pattern-Recognition Receptor, Enhances Peptidoglycan-Mediated Activation of the Drosophila Imd Pathway. Immunity. 45(5):1013-1023.

Dostálová A, Rommelaere S, Poidevin M, Lemaitre B. (2017) Thioester-containing proteins regulate the Toll pathway and play a role in Drosophila defence against microbial pathogens and parasitoid wasps. BMC Biol;15(1):79.

Iatsenko I, Boquete JP, Lemaitre B. (2018) Microbiota-Derived Lactate Activates Production of Reactive Oxygen Species by the Intestinal NADPH Oxidase Nox and Shortens Drosophila Lifespan. Immunity 49(5):929-942.

Hanson, M.A., Dostalova, A., Ceroni, C., Poidevin, M., Kondo, S. & Lemaitre B. (2019) Synergy and remarkable specificity of antimicrobial peptides in vivo using a systematic knockout approach. Pre-print available. Elife 8:e44341.

Melcarne, C., Ramond, E., Dudzic, J., Bretscher, A., Kurucz, É ., Andó, I., & Lemaitre B. (2019) Two Nimrod receptors, NimC1 and Eater, synergistically contribute to bacterial phagocytosis in Drosophila melanogaster. Pre-print available FEBS J. Jul;286(14):2670-2691.

Dudzic, J.P., Hanson, M.A., Iatsenko, I., Kondo, S. & Lemaitre B. (2019) More than black and white: complex relationships involving serine proteases regulate the Toll pathway and the melanization response in Drosophila. Cell reports, pr 23;27(4):1050-1061.

Parvy, J.P., Yu, Y., Dostalova, A., Kondo S., Kurjan, A., Bulet, P., Lemaitre, B., Vidal, M. and Cordero, J. (2019) The antimicrobial peptide Defensin cooperates with Tumour Necrosis Factor to drive tumour cell death in Drosophila. Elife. 2019 Jul 30;8. pii: e45061. Jul;286(14):2670-2691.

Hanson MA, Lemaitre B, Unckless RL.  (2019) Dynamic Evolution of Antimicrobial Peptides Underscores Trade-Offs Between Immunity and Ecological Fitness. Front Immunol. 10:2620. doi: 10.3389/fimmu.2019.02620.

Li X, Rommelaere S, Kondo S, Lemaitre B. (2020) Renal Purge of Hemolymphatic Lipids Prevents the Accumulation of ROS-Induced Inflammatory Oxidized Lipids and Protects Drosophila from Tissue Damage. Immunity. 2020 Feb 18;52(2):374-387.

Ramond E, Petrignani B, Dudzic JP, Boquete JP, Poidevin M, Kondo S, Lemaitre B. (2020) The adipokine NimrodB5 regulates peripheral hematopoiesis in Drosophila. FEBS J. 2020.

Hanson MA, Lemaitre B. (2020),New insights on Drosophila antimicrobial peptide function in host defense and beyond. Curr Opin Immunol. 62:22-30.

2) The Drosophila-Spiroplasma interaction: a model for insect endosymbiosis

Virtually every species of insect harbours facultative bacterial endosymbionts (ex. Wolbachia) that are transmitted from females to their offsprings. These symbionts play crucial roles in the biology of their hosts. Some manipulate host reproduction, for example, by killing the sons of infected females, in order to spread within host populations. Other symbionts protect their hosts against natural pathogens and parasites. However, in spite of growing interest in endosymbionts, very little is known about the molecular mechanisms underlying most endosymbiont-insect interactions. Our laboratory is studying the interaction between Drosophila and its endosymbiont Spiroplasma poulsonii. We are using a broad range of approaches ranging from molecular genetics to genomics to dissect the molecular mechanisms underlying key features of the symbiosis, including vertical transmission, male killing, regulation of symbiont growth, and symbiont-mediated protection against pathogens. We believe that the fundamental knowledge generated by studying the Drosophila-Spiroplasma interaction will serve as a paradigm for other endosymbiont-insect interactions that are less amenable to genetic studies.

Figure 2: Spiroplasma colonization of the germline. Spiroplasma uses the yolk uptake machinery to colonize the germline, ensuring vertical transmission. In this photo, Spiroplasma bacteria (stained in red) are colonizing the egg chamber (stained with phalloidin) during vitellogenesis. (Spiroplasma).
Figure 2: Spiroplasma colonization of the germline. Spiroplasma uses the yolk uptake machinery to colonize the germline, ensuring vertical transmission. In this photo, Spiroplasma bacteria (stained in red) are colonizing the egg chamber (stained with phalloidin) during vitellogenesis. (Spiroplasma).

Recent references

Ramond E, Maclachlan C, Clerc-Rosset S, Knott GW, Lemaitre B. (2016) Cell Division by Longitudinal Scission in the Insect Endosymbiont Spiroplasma poulsonii. MBio. Jul 26;7(4). pii: e00881-16.

Harumoto T, Anbutsu H, Lemaitre B, Fukatsu T. (2016) Male-killing symbiont damages host’s dosage-compensated sex chromosome to induce embryonic apoptosis. Nat Commun.7:12781

Masson F. and Lemaitre B. (2017) Protection from within. Elife. e24111.

Harumoto T, Fukatsu T, Lemaitre B. (2018) Common and unique strategies of male killing evolved in two distinct Drosophila symbionts. Proc Biol Sci. 285(1875).

Masson F, Calderon Copete S, Schüpfer F, Garcia-Arraez G, Lemaitre B. (2018) In Vitro Culture of the Insect Endosymbiont Spiroplasma poulsonii Highlights Bacterial Genes Involved in Host-Symbiont Interaction. MBio. 9(2). pii: e00024-18.

Garcia-Arraez MG, Masson F, Escobar JCP, Lemaitre B. (2019) Functional analysis of RIP toxins from the Drosophila endosymbiont Spiroplasma poulsonii. BMC Microbiol. 2019 Feb 20;19(1):46.

Masson F, Calderon-Copete S, Schüpfer F, Vigneron A, Rommelaere S, Garcia-Arraez MG, Paredes JC, Lemaitre B. Blind killing of both male and female Drosophila embryos by a natural variant of the endosymbiotic bacterium Spiroplasma poulsonii. Cell Microbiol.:e13156. doi: 10.1111/cmi.13156.

3) Science, Society and Narcissism

Increasing inequalities, rising individualism, distrust of institutions, tensions between cultures, increased social stress, instability of conjugal relationships… and if these characteristic evils of our time all shared the same origin, namely a change in narcissism expression?

How science generally perceived as an objective activity is affected by personalities and ego?

As a side projects of his research on innate immunity, Bruno Lemaitre use social personalities and evolutionary psychology to address these questions. He try to decipher how social dominance influences interactions between scientists within their community. He also explores how narcissism and possible change in expression of these traits can affect and destabilize Western societies.

Recent references

Lemaitre B (2016) An Essay on Science and Narcissism: How Do High‐ego Personalities Drive Research in Life Sciences? Autoedition, Lausanne.

Lemaitre B. (2016) Connecting the obesity and the narcissism epidemics. Med Hypotheses. 95:10-19. doi: 10.1016/j.mehy.2016.08.001.

Lemaitre B. (2017) Science, narcissism and the quest for visibility FEBS J. 284(6):875-882.

Lemaitre B. Les dimensions de l’ego. Séduction, dominance, manipulation: la société à l’épreuve des narcissiques. Edition Quanto 352 pages