Toll-like receptor adaptor protein TIRAP has specialized roles in signaling, metabolic control and leukocyte migration upon wounding in zebrafish larvae

The Toll-interleukin-1 Receptor (TIR) domain-containing adaptor protein (TIRAP), also known as MyD88-associated ligand (MAL), is an essential adaptor protein in Toll-like receptor 2 (TLR2) signaling which links TLR2 and TLR4 to the other adaptor protein myeloid differentiation protein 88 (MyD88). Here, we investigate the transcriptomic and metabolomic profiles of zebrafish larvae from a tirap mutant and a myd88 mutant and the corresponding wild type controls under unchallenged normal developmental conditions. Comparing data from tirap and myd88 mutants with published data on tlr2 mutant, we found that Tirap has specialized roles in signaling and metabolic control. Transcriptome analysis revealed the specific involvement of tirap in calcium homeostasis and myosin regulation. Metabolomic profiling showed that the tirap mutation results in lower glucose levels, whereas a tlr2 mutation leads to higher glucose levels. Previously, tlr2 and myd88 have been indicated to be involved in responses to wounding by regulating leukocyte migration in zebrafish, but the role of tirap in regulating leukocyte migration has still not been investigated. In this study, a tail-wounding zebrafish larval model was used to identify the specific roles of tirap in leukocyte migration to tissue wounding. We found that more neutrophils were recruited to the wounded region in the tirap mutant larvae compared to the wild type controls, whereas there was no difference in macrophage recruitment. In contrast, published data show that tlr2 and myd88 mutants recruit fewer neutrophils and macrophages to the wounds. We visualized neutrophil migration trajectories in tail-wounding tirap mutant and wild type zebrafish larvae. Based on cell tracking analysis, we demonstrated that the neutrophil migration speed is increased in the tirap mutant. This is in contrast to our published results for neutrophil behavior in myd88 and tlr2 mutants. In conclusion, our findings demonstrate that tirap plays specialized roles distinct from tlr2 and myd88 in signaling, metabolic control, and in regulating neutrophil migration speed upon wounding. Overall design: For the sequencing of tirap mutant zebrafish larvae, zebrafish larvae at 5 dpf from line tirap mutant and wild-type control were collected for RNAseq. For the sequencing of myd88 mutant zebrafish larvae, zebrafish larvae at 5 dpf from line myd88 mutant and wild-type control were collected for RNAseq.