Abstract
C1qs are key components of the classical complement pathway. They have been well documented in human and mammals, but little is known about their molecular and functional characteristics in fish. In the present study, full-length cDNAs of c1qA, c1qB, and c1qC from zebrafish (Danio rerio) were cloned, revealing the conservation of their chromosomal synteny and organization between zebrafish and other species. For functional analysis, the globular heads of C1qA (ghA), C1qB (ghB), and C1qC (ghC) were expressed in Escherichia coli as soluble proteins. Hemolytic inhibitory assays showed that hemolytic activity in carp serum can be inhibited significantly by anti-C1qA, -C1qB, and -C1qC of zebrafish, respectively, indicating that C1qA, C1qB, and C1qC are involved in the classical pathway and are conserved functionally from fish to human. Zebrafish C1qs also could specifically bind to heat-aggregated zebrafish IgM, human IgG, and IgM. The involvement of globular head modules in the C1q-dependent classical pathway demonstrates the structural and functional conservation of these molecules in the classical pathway and their IgM or IgG binding sites during evolution. Phylogenetic analysis revealed that c1qA, c1qB, and c1qC may be formed by duplications of a single copy of c1qB and that the C1q family is, evolutionarily, closely related to the Emu family. This study improves current understanding of the evolutionary history of the C1q family and C1q-mediated immunity.
Highlights
C1qs are key components of the classical complement pathway
C1q-like molecules have been identified in both lamprey [18] and amphioxus [19]. These molecules have been demonstrated to act as lectins and function as initial recognition molecules that connect the C1q to the lectin pathway and the innate immunity. These findings indicate that C1q may have a much longer evolutionary history than thought previously, and C1q molecules may have undergone a functional transition
The c1qA cDNA was 1148 bp in size, containing an open reading frames (ORFs) of 741 bp that translates to a 247-amino acid peptide, a 5Ј untranslated region (UTR) of 111 bp, and a 3Ј UTR of 293 bp
Summary
Experimental Fish—Zebrafish (Danio rerio, weighing ϳ0.5– 1.0 g) and Crucian carp (Carassius auratuses, weighing ϳ250 – 500 g) were kept in recirculating water at 26 °C and fed with commercial pellets at a daily ration of 0.7% of their body weight. After a number of C1q-like genomic sequence segments were obtained from the databases by BLAST [20], complete sequences of C1q domain-containing genes were obtained by retrieving neighboring regions, which was performed by zooming and scrolling over chromosomes in the Genome Browser These genomic sequences were used to search coding exons or open reading frames (ORFs) using the GENSCAN program (Massachusetts Institute of Technology) or the ORF finder programs at the NCBI Web site (http://www.ncbi.nlm.nih.gov/ gorf/gorf.html). The translated proteins from predicted transcripts were verified by BLAST [21] in the Swiss-Prot database Using this method, a sequence similar to the c1qC gene was obtained and was further analyzed using the GENSCAN [22], BLAST [23], and FASTA [24] programs. One week after final immunization, the rabbits were bled when antibody titers were above 1:10,000 as determined by microplate-based enzyme linked immunosor-
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
