title: Microfibrillar-associated protein 4 (MFAP4) genes in catfish play a novel role in innate immune responses.
abstract: The lectin pathway of the complement system is characterized by two groups of soluble pattern recognition molecules, mannose-binding lectins (MBLs) and ficolins. These molecules recognize and bind carbohydrates in pathogens and activate complement leading to opsonization, leukocyte activation, and direct pathogen killing. While MBLs have been reported in many fish species, ficolins do not appear to be present in the teleost lineage, despite their importance in invertebrate and higher vertebrate innate immunity. A protein with a similar fibrinogen-like domain, microfibrillar-associated protein 4, MFAP4, is present in fish, albeit with no described immune function. We examined whether MFAP4 genes in fish may potentially act as pathogen receptors in the absence of ficolin. We isolated and characterized five MFAP4 genes from channel catfish. Linkage mapping and phylogenetic analysis indicated that at least three of the catfish MFAP4 genes are tightly clustered on a single chromosome, suggesting that they may have arisen through tandem duplication. Divergent, duplicated families of MFAP4 genes are also present in other teleost species. Expression analysis of the catfish MFAP4 transcripts revealed unique patterns of homeostatic expression among the genes in gill, spleen, skin, liver, and muscle. Expression of the five MFAP4 transcripts showed significant changes in expression as soon as 4h after infection with either Edwardsiella ictaluri or Flavobacterium columnare with modulation of expression continuing up to 7 d following pathogen exposure. Several different tissues and gene-specific patterns were captured and transcript expression changes of >30-fold were observed over the course of the bacterial challenges. Our results suggest a novel role for MFAP4 in teleost immune responses.
authors.affiliation: Department of Fisheries and Allied Aquacultures, Auburn University, Auburn, AL 36849, USA.
authors.forename: Donghong
authors.initials: D
authors.lastname: Niu
authors.forename: Eric
authors.initials: E
authors.lastname: Peatman
authors.forename: Hong
authors.initials: H
authors.lastname: Liu
authors.forename: Jianguo
authors.initials: J
authors.lastname: Lu
authors.forename: Huseyin
authors.initials: H
authors.lastname: Kucuktas
authors.forename: Shikai
authors.initials: S
authors.lastname: Liu
authors.forename: Fanyue
authors.initials: F
authors.lastname: Sun
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.forename: Tingting
authors.initials: T
authors.lastname: Feng
authors.forename: Zunchun
authors.initials: Z
authors.lastname: Zhou
authors.forename: Jeffery
authors.initials: J
authors.lastname: Terhune
authors.forename: Geoff
authors.initials: G
authors.lastname: Waldbieser
authors.forename: Jiale
authors.initials: J
authors.lastname: Li
authors.forename: Zhanjiang
authors.initials: Z
authors.lastname: Liu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D020610:Edwardsiella ictaluri; D004756:Enterobacteriaceae Infections / Q000276:immunology / Q000662:veterinary; D016326:Extracellular Matrix Proteins / Q000235:genetics* / Q000276:immunology*; D029941:Fish Proteins / Q000235:genetics* / Q000276:immunology*; D045826:Flavobacteriaceae Infections / Q000276:immunology / Q000662:veterinary; D005417:Flavobacterium; D006801:Humans; D007059:Ictaluridae / Q000235:genetics* / Q000276:immunology* / Q000821:virology; D007113:Immunity, Innate; D008969:Molecular Sequence Data; D016415:Sequence Alignment
chemical_list: D016326:Extracellular Matrix Proteins; D029941:Fish Proteins