Identification of cDNA sequences encoding the complement components of Zebrafish (Danio rerio)

Zebrafish can be utilized for immunological research as a fish model that allows gene targeting, but lacks enough molecular and sequence information on the complement system, a humoral innate immune factor. The present study aimed at identification of all the major complement components at the molecular level with phylogenetic evidence. Complementary DNA sequences encoding Clq, Clr/s, C2 (B/C2-B), C3, C4, C5, C6, C7, C8, C9, factor B (B/C2-A), the mannose-binding lectin (MBL), two MBL-associated serine proteases, properdin, and factor I were identified by cloning from the hepatopancreas and by database mining. As reported for carp and trout, the presence of two distinct isotypes were confirmed for C3, C4, and C7 also in zebrafish, indicating the ancient evolutionary origin of their diversifications in the vertebrate lineage.