Prof. Dr. Maria Leptin

The Leptin group studies the mechanisms and forces that determine cell shape in Drosophila and uses the zebrafish to analyze innate immune signalling.

The innate immune system provides rapid defence against pathogens and also deals with non-pathogenic stresses. Macrophages and dendritic cells, two key players in this system, patrol the body and respond to stimuli from damaged cells via extra and intracellular sensors. We aim to understand how such signals are recognized and how the appropriate subcellular and intercellular responses are triggered. We have discovered that one family of sensors – the cytoplasmic NOD-like receptors (NLRs) – are particularly abundant in fish.

Fish model systems allow in vivo observation of physiological processes. Specifically, we watch pathogens and the cells that attack them. We use genetically and chemically engineered in vivo fluorescent reporters to assay immune and stress responses in real time and at high spatial and temporal resolution as the cells of the fish encounter pathogens and stress signals.

Our research: Inflammation and the microbiome

The zebrafish has a large repertoire of innate immune receptors, some expressed in unstimulated young fish. We do not know how the gut or epidermis use these receptors in mature fish to deal with the microbiome, but older fish in aquaria are more prone to developing disease, especially Microsporidia infection. Using our novel ASC:GFP knock-in to visualize inflammasome formation in vivo, we will study the development of normal and pathological inflammation in the gut and epidermis throughout the lifespan of the fish. The asc:gfp line will first show if aging fish display low grade inflammation similar to aging people, for which increasing inflammasome activity due to decreasing autophagy is at least one major cause. This in vivo ‘inflammaging’ paradigm will be combined with modulation of the aging process, for example by using telomerase mutants or autophagy mutants (p62, optineurin, dram1), and by manipulation of the microbiome. 

Our successes: The Leptin group discovered the gene family of NLRs in the zebrafish, traced its evolutionary history and provided data suggesting selection for variation in certain parts of the proteins, consistent with a role in pathogen interactions. We produced a now widely used tool to follow inflammosome mediated inflammation by live imaging in the whole organism, namely an endogenously GFP-tagged ASC protein, which forms specks in response to inflammasome activation. 

Our goals: We wish to understand the role of the large family of NLR pathogen sensors in epithelial immunity, i.e. in the interaction of the epithelia with pathogens in their environment, and the ASC-mediated downstream inflammatory pathway. This involves both the understanding of variation of the gene family in wild and lab fish populations, and the change in epithelial immunity during aging.

Our methods/techniques: We use the zebrafish as a model, in which we moduled the inflammatory system through genome editing techniques. We monitor effects by in vivo imaging at high temporal and spatial resolution. We use high-throughput genome analysis and sequencing methods to compare variation in the gene families between populations.