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Updated: Apr 23, 2026
Visualization of Macrophage Lytic Cell Death During Mycobacterial Infection in Zebrafish Embryos via Intravital Microscopy
Published on: January 9, 2019
Macrophage-expressed perforins mpeg1 and mpeg1.2 have an anti-bacterial function in zebrafish
Erica L Benard1, Peter I Racz, Julien Rougeot
1Institute of Biology, Leiden University, Leiden, The Netherlands.
Abstract:
Macrophage-expressed gene 1 (MPEG1) encodes an evolutionarily conserved protein with a predicted membrane attack complex/perforin domain associated with host defence against invading pathogens. In vertebrates, MPEG1/perforin-2 is an integral membrane protein of macrophages, suspected to be involved in the killing of intracellular bacteria by pore-forming activity. Zebrafish have 3 copies of MPEG1; 2 are expressed in macrophages, whereas the third could be a pseudogene. The mpeg1 and mpeg1.2 genes show differential regulation during infection of zebrafish embryos with the bacterial pathogens Mycobacterium marinum and Salmonella typhimurium. While mpeg1 is downregulated during infection with both pathogens, mpeg1.2 is infection inducible. Upregulation of mpeg1.2 is partially dependent on the presence of functional Mpeg1 and requires the Toll-like receptor adaptor molecule MyD88 and the transcription factor NFκB. Knockdown of mpeg1 alters the immune response to M. marinum infection and results in an increased bacterial burden. In Salmonella typhimurium infection, both mpeg1 and mpeg1.2 knockdown increase the bacterial burdens, but mpeg1 morphants show increased survival times. The combined results of these two in vivo infection models support the anti-bacterial function of the MPEG1/perforin-2 family and indicate that the intricate cross-regulation of the two mpeg1 copies aids the zebrafish host in combatting infection of various pathogens.
Insights
Macrophage-expressed gene 1 (MPEG1) proteins are crucial for host defense against bacteria. Zebrafish studies reveal that two MPEG1 gene copies are differentially regulated during infection, aiding in pathogen clearance.
Area of Science:
- Immunology
- Genetics
- Microbiology
Background:
- Macrophage-expressed gene 1 (MPEG1) encodes a protein with a pore-forming domain involved in host defense.
- Vertebrate MPEG1/perforin-2 is a macrophage membrane protein implicated in killing intracellular bacteria.
- Zebrafish possess three MPEG1 gene copies, with two expressed in macrophages.
Purpose of the Study:
- To investigate the roles of zebrafish mpeg1 and mpeg1.2 genes in host defense against bacterial pathogens.
- To elucidate the regulatory mechanisms of mpeg1.2 gene expression during infection.
- To understand the contribution of MPEG1/perforin-2 family members to innate immunity.
Main Methods:
- Differential gene expression analysis in zebrafish embryos infected with Mycobacterium marinum and Salmonella typhimurium.
- Gene knockdown experiments using morpholinos to assess the function of mpeg1 and mpeg1.2.
- Analysis of immune signaling pathways, including Toll-like receptor (TLR) and NFκB, in mpeg1.2 regulation.
Main Results:
- mpeg1 expression is downregulated, while mpeg1.2 is induced during zebrafish embryo infection.
- mpeg1.2 upregulation depends on functional Mpeg1, MyD88, and NFκB.
- Knockdown of mpeg1 increases bacterial burden in M. marinum infection.
- Knockdown of both mpeg1 and mpeg1.2 increases bacterial burden in S. typhimurium infection, but mpeg1 knockdown improves survival.
Conclusions:
- The MPEG1/perforin-2 family plays a significant anti-bacterial role in zebrafish.
- Differential regulation of mpeg1 gene copies is essential for effective host defense against diverse pathogens.
- Cross-regulation between mpeg1 and mpeg1.2 contributes to the zebrafish's ability to combat infections.
