MOLECULAR CLONING AND EXPRESSION ANALYSIS OF A LIVER EXPRESSED ANTIMICROBIAL PEPTIDE-2 IN JAPANESE EEL, ANGUILLA JAPONICA

Liver Expressed Antimicrobial Peptide 2 (LEAP-2), a cysteine-rich cationic antimicrobial peptide, plays a vital role in the host innate immune system. In the present study, the AJLEAP-2 gene was cloned from Japanese eel (Anguilla japonica) by RACE. The length of AJLEAP-2 cDNA was 450 bp including a 270 bp ORF that encodes a puta-tive 89-peptide. The peptide contained the conserved motif MTPFWR and the characteristic motif C-X5-C-X4-C-X4-C of LEAP-2. AJLEAP-2 has three exons similar to the counterpart from other vertebrates. The expression of AJLEAP-2 from tissue/organs of Japanese eel elver indicated the highest expression in liver that was five times higher than that of -actin, and then in intestine that was only 1/130 the amount in liver. Additionally, AJLEAP-2 was highly expressed in glass eel, which was almost twice the amount in elver intestine. LPS and Edwardsiella tarda increased the expression of AJLEAP-2 in blood and reached the peak level at 16h post challenge increasing 86 folds and 12 folds, respectively. Both LPS and E. tarda significantly up-regulated the expression of AJLEAP-2 in intestine. Meanwhile, the transcript level of AJLEAP-2 in blood was significantly down-regulated at 24h challenged with Poly I:C. These results suggest that AJLEAP-2 may play an important role in innate immunity of Japanese eel against bacterial infection.