AUTHOR=Sebo Dylan J. , Fetsko Audrey R. , Phipps Kallie K. , Taylor Michael R. 

TITLE=Functional identification of the zebrafish Interleukin-1 receptor in an embryonic model of Il-1β-induced systemic inflammation

JOURNAL=Frontiers in Immunology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2022.1039161

DOI=10.3389/fimmu.2022.1039161

ISSN=1664-3224

ABSTRACT=<p>Interleukin-1β (IL-1β) is a potent proinflammatory cytokine that plays a vital role in the innate immune system. To observe the innate immune response <italic>in vivo</italic>, several transgenic zebrafish lines have been developed to model IL-1β-induced inflammation and to visualize immune cell migration and proliferation in real time. However, our understanding of the IL-1β response in zebrafish is limited due to an incomplete genome annotation and a lack of functional data for the cytokine receptors involved in the inflammatory process. Here, we use a combination of database mining, genetic analyses, and functional assays to identify zebrafish Interleukin-1 receptor, type 1 (Il1r1). We identified putative zebrafish <italic>il1r1</italic> candidate genes that encode proteins with predicted structures similar to human IL1R1. To examine functionality of these candidates, we designed highly effective morpholinos to disrupt gene expression in a zebrafish model of embryonic Il-1β-induced systemic inflammation. In this double transgenic model, <italic>ubb:Gal4-EcR</italic>, <italic>uas:il1β<sup>mat</sup></italic>, the zebrafish <italic>ubiquitin b</italic> (<italic>ubb</italic>) promoter drives expression of the modified Gal4 transcription factor fused to the ecdysone receptor (EcR), which in turn drives the tightly-regulated expression and secretion of mature Il-1β only in the presence of the ecdysone analog tebufenozide (Teb). Application of Teb to <italic>ubb:Gal4-EcR</italic>, <italic>uas:il1β<sup>mat</sup></italic> embryos causes premature death, fin degradation, substantial neutrophil expansion, and generation of reactive oxygen species (ROS). To rescue these deleterious phenotypes, we injected <italic>ubb:Gal4-EcR</italic>, <italic>uas:il1β<sup>mat</sup></italic> embryos with putative <italic>il1r1</italic> morpholinos and found that knockdown of only one candidate gene prevented the adverse effects caused by Il-1β. Mosaic knockout of <italic>il1r1</italic> using the CRISPR/Cas9 system phenocopied these results. Taken together, our study identifies the functional zebrafish Il1r1 utilizing a genetic model of Il-1β-induced inflammation and provides valuable new insights to study inflammatory conditions specifically driven by Il-1β or related to Il1r1 function in zebrafish.</p>