Kininogens, the precursors of bradykinins, ubiquitously exist in vertebrates, including mammals, birds, amphibians, and fishes. To elucidate the phylogeny of kininogen genes in early vertebrates, we cloned the full-length cDNA of kininogen gene from the liver of Lampetra japonica. The open reading frame of this sequence contained 546 bp and encoded 181 amino acids, including a cystatin domain without the canonical binding site for cysteine proteinases and a bradykinin domain. Our results suggested that in lampreys and most of other vertebrates, there might be only one kininogen gene, which was fused by certain sequences during vertebrate evolution and encoded proteins with more functions; however, another special kininogen gene, only encoding the bradykinin domain with multiple copies in some species, arose only in amphibians for adapting themselves to the unique environment. Using reverse transcription PCR, kininogen mRNA was also detected in lamprey gut, kidney, and leukocyte, but absent in lamprey buccal gland. Our findings may provide insights into the phylogeny of kininogen genes as well as other gene families in vertebrates.
A cDNA library was constructed from the liver of Lampetra japonica. 10077 ESTs were obtained by random selecting clones for sequencing. The results demonstrated that 8515 ESTs were assembled into 648 consensus sequences, represented 2210 unique transcripts, 47.06% of which were predicted as full length cDNAs. In addition, 1562 ESTs were singlets. Using the BLAST to align the assembled ESTs, we found that 93.9% (2053) transcripts shared similarity to sequences published in GenBank databases. The functional annotations to assembled ESTs showed that the genes, involved in immu-nology, blood coagulation and metabolism of jawed vertebrates, were highly expressed in the liver of L. japonica. Furthermore, 8 potential novel genes were identified. Further comparing liver transcriptome of L. japonica with Fundulus heteroclitus, Mus musculus, Bos Taurus, and Homo sapiens revealed that the genes of Chitinase and Polysaccharides metabolism were more highly expressed in L. japonica than the others, which implied that they may play an important role in immunity of L. japonica. In addi-tion, using the TargetScan, we marked microRNA target within 3′ UTR of L. japonica liver transcriptome. The data indicated that some microRNA targets were homology with the targets embeded in human cancer genes. The result seems to provide a useful clue to the treatment of human cancer. Therefore, the present work will be an important resource for investigating the functional genomics and pro-teomics of L. japonica as well as evolution of vertebrates.
ZHU LiNa1, DAI YaLi2, MA Fei1 & LI QingWei1 1 College of Life Sciences, Liaoning Normal University, Dalian 116029, China
