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Expansion of genes encoding complement components in bony fish: biological implications of the complement diversity
Miki Nakao1, Junichi Mutsuro, Makiko Nakahara
1Laboratory of Marine Biochemistry, Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Hakozaki, 812-8581, Fukuoka, Japan. miki_n@agr.kyushu-u.ac.jp
Developmental and Comparative Immunology
|June 24, 2003
Summary
The carp complement system exhibits remarkable gene expansion, producing diverse functional proteins. This diversity in immune components suggests a more complex defense mechanism in bony fish compared to mammals.
Area of Science:
- Immunology
- Molecular Biology
- Evolutionary Biology
Background:
- The complement system is crucial for vertebrate innate immunity, identifying and eliminating pathogens.
- Bony fish possess a unique complement system characterized by multiple genes encoding several complement components.
Purpose of the Study:
- To review the structural and functional diversity of complement components in bony fish, with a focus on the common carp (Cyprinus carpio).
- To explore the implications of expanded gene families and functional differentiation in the carp complement system.
Main Methods:
- Comparative analysis of structural diversity in complement components (C3, C4, C5, factor B, C2, C1r/s, MASP) across species.
- Focus on primary structures and functional sites of carp complement proteins.
- Examination of expression patterns and potential functional differences of carp complement isotypes.
Main Results:
- Carp exhibit multiple isotypes for thioester-containing proteins (C3, C4, C5, alpha2-macroglobulin) with distinct primary structures.
- Three factor B/C2-like isotypes in carp show varied expression patterns, including acute-phase reactivity.
- Two C1r/C1s/MASP2-like isotypes in carp possess substitutions potentially altering substrate specificity.
Conclusions:
- The carp complement system displays greater functional diversity than previously known in mammals due to expanded gene families.
- This molecular diversity likely contributes to enhanced or specialized immune responses in bony fish.
- Further research is needed to elucidate the precise biological significance of this expanded complement system in carp.