Molecular cloning and functional analysis of zebrafish (Danio rerio) chemokine genes

Chemokines control leukocyte trafficking which plays important roles in resistance to pathogenic infection. Five CXC chemokines have been reported in the zebrafish (Danio rerio) in GenBank, and herein we named them CXC-46, -56, -64, -66, and scyba. Through RT-PCR for cloning and sequencing these chemokines, the cDNA sequences of CXC-46, -56, -64, and -66 of zebrafish were determined, and it was found that the cDNA sequences were the same as those published in GenBank. Phylogenetic analysis revealed that zebrafish scyba is closest to the CXCL14 subgroup, CXC-46 is closest to the human CCL25 and catfish CXCL-2-like gene, and CXC-56, -64, and -66 are closest to the catfish CXCL10 subgroup. Further study of the tissue-specific, lipopolysaccharide (LPS) stimulation-specific, and polyinosinic-polycytidylic acid (poly I:C) stimulation-specific expressions of these five zebrafish CXC chemokine messenger (m)RNAs were determined by a comparative reverse-transcription polymerase chain reaction (RT-PCR). The RT-PCR revealed a high level of constitutive expression of CXC-56 in many tissues including the eyes, fins, heart, liver, muscles, and skin. Starvation had significant effects on the gene expressions of several zebrafish CXC chemokines including CXC-56, -64, -66, and scyba compared to the control group. Zebrafish CXC chemokines showed a concave pattern of expression after stimulation with LPS. Following poly I:C treatment of between 0.1 and 10 g/fish, dose-dependent effects were revealed. Temperature and acid-base conditions affected these zebrafish chemokines by increasing their induction compared to the control group, except for CXC-64 which exhibited no significant differences in either condition. Furthermore, these novel research results indicate that chemokines can be markers of different experimental conditions.