title: Functional characterization of mannose-binding lectin in zebrafish: implication for a lectin-dependent complement system in early embryos.
abstract: The lectin pathway involves recognition of pathogen-associated molecular patterns by mannose-binding lectin (MBL), and the subsequent activation of associated enzymes, termed MBL-associated serine proteases (MASPs). In this study, we demonstrate that the transcript of MBL gene is present in the early embryo of zebrafish, and MBL protein is also present in the embryo. In addition, we show that recombinant zebrafish MBL was able to bind the Gram-negative bacterium Escherichia coli and the Gram-positive bacterium Staphylococcus aureus, and rMBL was able to promote the phagocytosis of E. coli and S. aureus by macrophages, indicating that like mammalian MBL, zebrafish MBL performs a dual function in both pattern recognition and opsonization. Importantly, we show that microinjection of anti-MBL antibody into the early developing embryos resulted in a significantly increased mortality in the embryos challenged with Aeromonas hydrophila (pathogenic to zebrafish); and injection of rMBL into the embryos (resulting in increase in MBL in the embryo) markedly promoted their resistance to A. hydrophila; and this promoted bacterial resistance was significantly reduced by the co-injection of anti-MBL antibody with rMBL but not by the injection of anti-actin antibody with rMBL. These suggest that the lectin pathway may be already functional in the early embryos in zebrafish before their immune system is fully matured, protecting the developing embryos from microbial infection. This work provides a new angle to understand the immune role of the lectin pathway in early development of animals.
authors.affiliation: Laboratory for Evolution & Development, Institute of Evolution & Marine Biodiversity and Department of Marine Biology, Ocean University of China, China.
authors.forename: Lili
authors.initials: L
authors.lastname: Yang
authors.affiliation: Laboratory for Evolution & Development, Institute of Evolution & Marine Biodiversity and Department of Marine Biology, Ocean University of China, China.
authors.forename: Lingzhen
authors.initials: L
authors.lastname: Bu
authors.affiliation: Laboratory for Evolution & Development, Institute of Evolution & Marine Biodiversity and Department of Marine Biology, Ocean University of China, China.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Sun
authors.affiliation: Laboratory for Evolution & Development, Institute of Evolution & Marine Biodiversity and Department of Marine Biology, Ocean University of China, China.
authors.forename: Lili
authors.initials: L
authors.lastname: Hu
authors.affiliation: Laboratory for Evolution & Development, Institute of Evolution & Marine Biodiversity and Department of Marine Biology, Ocean University of China, China. Electronic address: sczhang@ouc.edu.cn.
authors.forename: Shicui
authors.initials: S
authors.lastname: Zhang
mesh_terms: D056704:Adaptive Immunity; D016980:Aeromonas hydrophila / Q000276:immunology; D000595:Amino Acid Sequence; D000818:Animals; D003167:Complement Activation; D003165:Complement System Proteins; D004625:Embryo, Nonmammalian / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D005260:Female; D005393:Fish Diseases / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D016905:Gram-Negative Bacterial Infections / Q000276:immunology / Q000378:metabolism / Q000662:veterinary*; D007113:Immunity, Innate; D008297:Male; D037601:Mannose-Binding Lectin / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D010587:Phagocytosis; D011485:Protein Binding; D015027:Zebrafish / Q000235:genetics / Q000276:immunology* / Q000378:metabolism
chemical_list: D037601:Mannose-Binding Lectin; D003165:Complement System Proteins
keywords: Lectin complement pathway; Mannose-binding lectin; Maternal immunity; Phagocytosis; Zebrafish