Evolution of teleostean hatching enzyme genes and their paralogous genes
Evolution of teleostean hatching enzyme genes and their paralogous genes
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DOI：
10.1007/s00427-006-0104-5
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发表时间：
2006-12-01
影响因子：
2.4
通讯作者：
Iuchi, Ichiro
中科院分区：
文献类型：
--
作者：
Kawaguchi, Mari;Yasumasu, Shigeki;Iuchi, Ichiro
我们分离出孵化酶的基因和它们的旁系同源物，除了在所有的astacin家族蛋白酶中保守的四个半胱氨酸外，它们的N-末端区域还具有两个半胱氨酸残基。在青鳉基因组数据库中搜索这种含六个半胱氨酸的astacin蛋白酶（C6 AST）的基因。除了胚胎特异性孵化酶基因外，还发现了MC 6AST 1至5的5个基因。RT-PCR和整体原位杂交结果表明，MC 6AST 1在胚胎和几乎所有成体组织的表皮中均有表达，而MC 6AST 2和3在肠系膜、肠和睾丸中均有表达。MC 6AST 4和5在颌骨中特异性表达。此外，我们还从斑马鱼、香鱼和东方鲀中克隆了C6 AST cDNA同源物。MC 6AST 1 ~ 5基因在系统发育位置上可分为3类，其表达模式和孵化酶与其它C6 ASTs基因有明显区别。外显子-内含子结构分析表明，孵化酶MHCE和MAHCE的基因是无内含子的，而其他MC 6AST基因与另一种孵化酶MLCE的基因基本相同。在基础硬骨鱼中，具有祖先外显子-内含子结构（9个外显子/8个内含子结构）的C6 AST基因首先通过复制和染色体易位出现。此后，保持这种祖先的外显子-内含子结构，LCE基因是新的多样化真骨鱼，和MC 6AST 1至5基因直系同源物的复制和多样化，在各自的鱼谱系独立。HCE基因在真骨鱼中丢失了所有的内含子，而在斑马鱼的谱系中，它在染色体之间移位并丢失了一些内含子。
We isolated genes for hatching enzymes and their paralogs having two cysteine residues at their N-terminal regions in addition to four cysteines conserved in all the astacin family proteases. Genes for such six-cysteine-containing astacin proteases (C6AST) were searched out in the medaka genome database. Five genes for MC6AST1 to 5 were found in addition to embryo-specific hatching enzyme genes. RT-PCR and whole-mount in situ hybridization evidenced that MC6AST1 was expressed in embryos and epidermis of almost all adult tissues examined, while MC6AST2 and 3 were in mesenterium, intestine, and testis. MC6AST4 and 5 were specifically expressed in jaw. In addition, we cloned C6AST cDNA homologs from zebrafish, ayu, and fugu. The MC6AST1 to 5 genes were classified into three groups in the phylogenetic positions, and the expression patterns and hatching enzymes were clearly discriminated from other C6ASTs. Analysis of the exon-intron structures clarified that genes for hatching enzymes MHCE and MAHCE were intron-less, while other MC6AST genes were basically the same as the gene for another hatching enzyme MLCE. In the basal Teleost, the C6AST genes having the ancestral exon-intron structure (nine exon/eight intron structure) first appeared by duplication and chromosomal translocation. Thereafter, maintaining such ancestral exon-intron structure, the LCE gene was newly diversified in Euteleostei, and the MC6AST1 to 5 gene orthologs were duplicated and diversified independently in respective fish lineages. The HCE gene lost all introns in Euteleostei, whereas in the lineage to zebrafish, it was translocated from chromosome to chromosome and lost some of its introns.