鱼类Ⅰ型与Ⅱ型胶原蛋白基因系统进化及其在有/无肌间骨代表鱼中的表达比较分析

研究在分析鱼类Ⅰ型与Ⅱ型胶原蛋白基因系统进化基础上, 以有肌间骨的团头鲂(Megalobrama amblycephala)和无肌间骨的尼罗罗非鱼(Oreochromis niloticus)为研究对象, 探究了Ⅰ型与Ⅱ型胶原蛋白基因在二者不同发育阶段及不同部位肌肉组织中的表达模式。系统进化分析结果显示, 胶原蛋白基因col1a1、col1a2和col2a1在有刺鱼和无刺鱼中均各自聚为一支, 团头鲂和罗非鱼3个基因的氨基酸同源性都在90%以下。不同部位肌肉组织(背部上方、尾部上方和尾部下方)的基因表达结果显示, 团头鲂col1a1a和col1a1b基因与罗非鱼该同源基因col1a1在不同肌肉组织中的表达模式存在明显差异。在团头鲂中, Ⅰ型与Ⅱ型胶原蛋白基因在背上肌肉中的表达量高于尾部; 而在罗非鱼中, 其表达模式则相反。团头鲂和罗非鱼不同发育时期的基因定量结果显示: 团头鲂col1a1a和col2a1b基因的表达在肌间骨出现以前(15 dph)和基本出现之后(50 dph)显著(P<0.01)增加, 且Ⅰ型胶原蛋白基因和col2a1b的相对表达量在不同时期差异明显, 其中col1a1a基因在50 dph的表达丰度极高; 与团头鲂相比, 罗非鱼中相应基因的表达量变化较小, 整体波动不大。研究揭示了Ⅰ型和Ⅱ型胶原蛋白在有刺鱼与无刺鱼肌肉中的表达模式, 结果表明col1a1在团头鲂和尼罗罗非鱼两种鱼类中表达模式显著不同(P<0.01), 推测其与肌间骨发育潜在相关。

PHYLOGENY AND COMPARATIVE EXPRESSION ANALYSIS OF TYPE Ⅰ AND TYPE Ⅱ COLLAGEN GENES IN THE REPRESENTATIVE FISH SPECIES WITH AND WITHOUT INTERMUSCULAR BONES

Intermuscular bone(IB)is a type of membrane bone that derive from the continuous homogeneous ossification of the connective tissue in fish muscle.Collagen genes involved in the regulation of vertebrate bone mineralization,but it is not clear whether its expression is related to the development of fish intermuscular bones.In order to study the correlation among collagen genes and IB formation,this study first analyzed the phylogenetic evolution of type Ⅰ and Ⅱ collagen genes in fish;then compared genes expression levels at different stages and tissues between Megalobrama amblycephala with intermuscular bones and Oreochromis niloticus without intermuscular bones.Phylogenetic analysis of the collagen genes col1a1,col1a2 and col2a1 showed that fish species with IB and species without IB were clustered into different branches,and the amino acid homology of M.amblycephala and O.niloticus genes was less than 90%.There were significant differences between the expression levels of col1a1a and col1a1b genes in M.amblycephala and homologous genes col1a1 in O.niloticus in several muscle(dorsal,upper caudal and lower caudal muscles).In M.amblycephala,the expression levels of type Ⅰ and type Ⅱ collagen genes in the dorsal muscle were higher than those in the caudal muscle;however,in O.niloticus,the expression of these genes was opposite to that of M.amblycephala.The expression of col1a1a and col2a1b genes of M.amblycephala increased significantly before the appearance of intermuscular bones(15 dph)and after the appearance of all intermuscular bones(50 dph).The relative expression of type Ⅰ collagen gene and col2a1b were significantly different in different periods,and the expression abundance of col1a1a at 50 dph was extremely high.Compared with M.amblycephala,the expression change of these genes in Oreochromis niloticus were small,and the overall fluctuation was not large.These results revealed that the expression level and pattern of col1a1 in two species were significantly different(P<0.01),therefore we speculate that col1a1 is potentially related to the development of IB.