Zebrafish complement factor H and its related genes: identification, evolution, and expression

The complement system consists of a number of serum and membrane-bound proteins that play a crucial role in protecting the host organism against microbial infection. Complement factor H (CFH) regulates the alternative pathway of complement in plasma and mediates discrimination of cellular surfaces to alternative pathway activators and non-activators. Although complement system of zebrafish has been extensively studied, the information regarding CFH and its related genes in this important model species remains lacking. In this study, we report the molecular cloning and identification of CFH and complement factor H-like 1-4 (CFHL1-4) in Danio rerio. Sequence comparison and phylogenetic, syntenic, as well as genomic structure analyses demonstrated that the scaffold encompassing CFH and CFHLs region was conserved during evolution from bony fish to humans, and CFH and CFHL1-4 originated by intra-chromosome duplication on chromosome 22. Besides, quantitative real-time polymerase chain reaction revealed that both zebrafish CFH and CFHLs were predominantly expressed in the liver in a tissue-specific manner, and their expression was inducible by lipopolysaccharide, an inducer of immune responses, suggesting that they are possibly involved in acute phase responses. These are the first such data in bony fish, laying a foundation for further study of their physiological functions.