寄生扁虫副肌球蛋白的适应性进化及副肌球蛋白基因在后生动物中的进化研究
文献类型：学位论文
| 作者 | 谢钢琴 |
| 学位类别 | 硕士 |
| 答辩日期 | 2014-11 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 文建凡 |
| 关键词 | 寄生扁虫 免疫逃避 副肌球蛋白 系统分布 进化 |
| 中文摘要 | 寄生扁虫（包括吸虫和绦虫）生活在宿主的血液或肠道内，面对宿主的免疫环境，已发展出了成功的免疫逃避机制。有研究显示曼氏血吸虫的副肌球蛋白能结合宿主补体分子C8/C9，从而抑制补体系统的激活，显示出在免疫逃避中发挥了重要作用。但该蛋白的这一免疫逃避功能是否在所有寄生扁虫中普遍存在，是否确是寄生适应性进化的结果尚不清楚，而且其发挥该功能的具体分子机制也还有待阐明。另外，副肌球蛋白作为肌肉的重要组成，其在后生动物中的分布和进化还未有系统的研究。本文主要利用生物信息学的技术方法对寄生扁虫中副肌球蛋白的寄生适应性进行了分析研究，并对副肌球蛋白基因在后生动物中的进化进行了系统研究，得到了以下结果及结论： 首先，从已具有基因组数据的曼氏血吸虫、日本血吸虫、华支睾吸虫、猪带绦虫、微小膜壳绦虫、细粒棘球绦虫、多房棘球绦虫和地中海圆头涡虫等八个扁虫中鉴定了它们的副肌球蛋白基因和蛋白序列，并通过EST拼接还获得了日本三角涡虫的副肌球蛋白序列。分析发现这些扁虫均不同于一般的动物只具有一个该蛋白的基因，而是具有两个基因。基因结构比较和系统发育分析的结果表明这两个副肌球蛋白基因是通过复制形成。其中寄生种类的一个拷贝与曼氏血吸虫的上述能结合补体的副肌球蛋白基因结构相似、其编码的蛋白序列也与后者很相似；相对于自由生活的涡虫的副肌球蛋白，寄生种类的这一蛋白存在一些不同的氨基酸位点及缺失片段，如：日本血吸虫副肌球蛋白的754和866位点氨基酸均为疏水性的亮氨酸和甲硫氨酸，这可能与形成结合补体的位点和空间结构有关；而838与839位点间存在缺失片段，这可能对于该蛋白形成有利于结合补体的结构有关。这些结果表明寄生扁虫通过寄生适应性进化形成了一种普遍的免疫逃避机制；其副肌球蛋白的一个拷贝进化形成了能结合补体C8/C9的特定区域，通过与宿主补体的结合而产生免疫逃避的效果。 其次，我们鉴定了后生动物中152个物种的副肌球蛋白基因，并利用基因结构比较和系统发育分析的方法对副肌球蛋白基因在后生动物中的进化问题进行了研究。结果表明副肌球蛋白仅分布于原口动物，而在侧生动物、辐射对称动物和后口动物均不具有副肌球蛋白；副肌球蛋白基因是由II型肌球蛋白重链复制产生。同时我们对副肌球蛋白基因在后生动物中仅分布于原口动物而在其它动物类群无分布的原因进行了探讨：侧生动物、辐射对称动物不同于两侧对称动物(原口动物和后口动物)，它们的肌细胞是独立进化出的，这类肌细胞本身就缺少包括副肌球蛋白的一些重要成分，换言之，这两类动物根本就未进化出副肌球蛋白；我们对与副肌球蛋白密切相关的四种肌肉类型（平滑肌，横纹肌，斜纹肌和心肌）、骨骼类型（外骨骼与内骨骼）进行分析，发现它们的类型与副肌球蛋白的分布均无相关性。结合已有的有关粗丝长度的研究，我们对动物肌肉粗丝的长度进行了比较，发现存在副肌球蛋白的动物肌肉粗丝相对于不含副肌球蛋白的粗丝长度更长，而且也有报道指出存在副肌球蛋白的肌肉粗丝结构更稳定，这与副肌球蛋白基因在原口动物中有而在后口动物无的分布特征相符合，因而这可能是副肌球蛋白仅存在于原口动物而在后口动物中发生了丢失功能选择方面的原因. |
| 英文摘要 | Parasitic flatworms (including flukes and tapeworms) live in the blood or gut of the host, it has evolved succeed immune escape mechanisms when facing the host immune environment. Studies have shown that paramyosin in the Schistosoma mansoni can be used to bind host complement C8/C9, thereby inhibiting the activation of the complement system. This indicated that the protein plays an important role in the parasite's immune evasion. However, the immune evasion function of paramyosin whether is prevalent and parasitic adaptive evolution of all the parasitic flatworms is not clear, but it plays the function of the specific molecular mechanisms have yet to be understood. In addition, paramyosin as an important component in the muscles, it has not yet a systems research of distribution and evolution in the metazoan. We obtain the following results and conclusions that through bioinformatics methods to study the adaptability of paramyosin in the parasitic flat worms, and the evolution of paramyosin gene in the metazoan: First, we identified paramyosin from genomic data in the Schistosoma mansoni、S. japonicum、Clonorchis sinensis、Taenia solium, Hymenolepis nana、Echinococcus granulosus、E. Multi and Schmidtea mediterranea, and obtained S.japonicum’s paramyosin gene and protein sequence by EST assembling method. Analysis found that these flatworms are different from general animals with only one of the paramyosin genes, but they have two genes. By comparing gene structure and phylogenetic analysis showed that these two paramyosin genes are formed by replication. One copy is similar with S.mansoni capable of binding complement paramyosin gene structure, the encoded protein sequence is also very similar with the latter; compare to the free-living planarian’s paramyosin, these proteins exist a series of specific amino acid sites and segments, such as: 754 and 866 amino acid sites from S.japonicum’s paramyosin are hydrophobic Leucine and Methionine, which may be combined with formation of complement loci and spatial structure, and there is a missing fragment between 839 and 838 sites, which may be for the protein to combination of complement of molecular structure. These results suggest that the parasitic flatworms through adaptive evolution formed a kind of common parasitic immune escape mechanism: a copy of this kind of paramyosin evolved a specific area that could combine complement C8 / C9, produced immune escape through the combination with the host complement. Secondly, we identified the paramyosin gene in the 152 species from the metazoan, then study the evolution of paramyosin gene in the metazoan by comparing gene structure and phylogenetic analysis. The results show that paramyosin is only distributed in the Protostome, and in the Parazoa, Radiata and Deuterostomia have not paramyosin; and paramyosin gene is formed by myosin heavy chain II replication. At the same time, we have explored the reason of paramyosin genes only distributed in protostome but didn’t exist other animal groups: compare to the Bilateria(including Protostome and Deuterostomia ), the muscle cells of the Parazoa and Radiata are independent evolved, and their had missing some important components, including paramyosin, in other words, these two kinds of animals did not evolve paramyosin; we analyzed four types of muscle(smooth muscle, striated muscle, oblique muscle and myocardium)、 and skeleton type(exoskeleton and endoskeleton) that closely related with paramyosin, and found their types and distribution of paramyosin have no correlation. Combined existing research about the thick filament length, we compared the length of thick filament and found that the presence of paramyosin in the thick filament contrast with no paramyosin could be longer, and there is also reported that the structure of presence paramyosin in the thick filament clouded be more stable, it accord with that paramyosin distribution in the Protostome but losed in the Deuterostomia , so it ma |
| 语种 | 中文 |
| 源URL | [http://159.226.149.26:8080/handle/152453/10086]  |
| 专题 | 昆明动物研究所_真核细胞进化基因组 |
| 作者单位 | 中国科学院昆明动物研究所 |
| 推荐引用方式 GB/T 7714 | 谢钢琴. 寄生扁虫副肌球蛋白的适应性进化及副肌球蛋白基因在后生动物中的进化研究[D]. 北京. 中国科学院研究生院. 2014. |
入库方式： OAI收割
来源：昆明动物研究所
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