The work presented in this thesis has provided new insights into the mechanisms involved in the regulation of innate immune responses in zebrafish embryos. Furthermore, cell-specific transcriptome... Show moreThe work presented in this thesis has provided new insights into the mechanisms involved in the regulation of innate immune responses in zebrafish embryos. Furthermore, cell-specific transcriptome profiling studies identified novel marker genes for distinguishing immune cell types, which is highly useful information to fulfill the demand for new fluorescent reporter lines and lineage-specific antibodies in the zebrafish model. We have shown that Ptpn6, a protein tyrosine phosphatase homolog of human SHP1, functions as a critical negative regulator, required for a properly balanced innate immune response and for controlling infections with bacterial pathogens. In Salmonella typhimurium infection, ptpn6 deficiency caused a general hyperinduction of pro-inflammatory genes, which was contraproductive as it impaired the infection control. In Mycobacterium marinum infection, a more specific effect of ptpn6 deficiency on matrix metalloproteinase gene expression was found as a major underlying cause of increased bacterial burden. We further concluded that Ptpn6 functions as a much stronger negative regulator than infection-inducible miRNAs of the miR-146 family, which may be involved in more subtle fine-tuning of the innate immune response. Knowledge about the distinct roles of Ptpn6 and miR-146 miRNAs has practical applicability in regard to their potential as therapeutic targets for inflammatory diseases and cancer. Show less
