DNA甲基化对猪反转座基因的起源、演化及生存的作用

发布时间：2018-08-02 12:26

【摘要】：DNA甲基化属于表观遗传学修饰,这类修饰具有稳定且可遗传的特点,可以在不改变DNA序列的前提下,调控基因的转录水平。反转座基因是指,在反转座酶的作用下,其父基因表达的m RNA经过反转录形成c DNA后,插入到基因组中新的位置,从而形成一个新的基因。反转座基因是生物发生演化的重要驱动力之一。然而,目前还未有人深入研究过DNA甲基化对猪的反转座基因的起源、演化及生存的作用。为此,我们通过分析猪中8个不同组织的简化代表性亚硫酸氢盐测序(reduced representation bisulfite sequencing,RRBS)数据和与之相对应的转录组数据,来研究反转座基因的DNA甲基化修饰机制,主要研究结果如下:1.在猪中一共鉴定了964个反转座拷贝,其中有560个反转座拷贝对猪新基因的起源有着重大贡献。2.通过GO富集和KEGG通路分析,发现新基因多与脂质代谢和多糖的生物合成有关。因此我们推测,反转座新基因的产生有利于猪中蛋白质和脂肪的积累。3.在不同的基因结构区域中,父基因呈现了不一样的DNA甲基化趋势,而反转座基因均呈现出高甲基化趋势。我们发现,父基因在基因体(gene body)区呈现出低甲基化水平,这使得父基因转录的m RNA有更大的几率被反转录,产生更多的反转座拷贝,从而有利于反转座拷贝的起源。而反转座基因则一直呈现出高甲基化水平,可能是出于一种防卫机制——防止反转座基因因产生个别有害突变,在选择压力的作用下被过早地剔除掉。反转座基因的高甲基化可以增加基因的突变率,从而更有利于其在短时间内积累更多的突变,在自然选择的作用下,个别有利的突变有助于它们的生存。4.父基因和反转座基因在基因体区的DNA甲基化受到选择压力的影响。5.反转座基因在启动子区域的DNA甲基化水平随着演化时间发生改变,并且调控着反转座基因的表达。综上所述,研究结果一方面证明了反转座事件有利于猪的新基因的形成,另一方面探讨了DNA甲基化修饰在猪的反转座基因的起源、演化和生存中起到的重要的调控作用。
[Abstract]:DNA methylation is an epigenetic modification, which has the characteristics of stability and heredity, and can regulate the transcription level of the gene without changing the DNA sequence. The reverse locus gene refers to the expression of m RNA of its parent gene after reverse transcription to form c DNA and insert into a new position in the genome to form a new gene under the action of reverse locus enzyme. Reverse locus gene is one of the important driving forces of biological evolution. However, no one has studied the role of DNA methylation in the origin, evolution and survival of porcine reverse locus gene. Therefore, we studied the DNA methylation mechanism of reverse locus gene by analyzing the simplified (reduced representation bisulfite sequencing data and the corresponding transcriptome data from 8 different tissues in pigs. The main results are as follows: 1. A total of 964 reverse locus copies have been identified in pigs, of which 560 have contributed significantly to the origin of new porcine genes. Through go enrichment and KEGG pathway analysis, it was found that the new gene was related to lipid metabolism and polysaccharide biosynthesis. Therefore, we speculate that the production of a new gene reverse locus is beneficial to the accumulation of protein and fat. 3. In different regions of gene structure, the parent gene showed a different trend of DNA methylation, while the reverse locus gene showed a tendency of hypermethylation. We found that the paternal gene showed a low methylation level in the (gene body) region of the gene, which made the m RNA transcribed by the parent gene more likely to be reversed, resulting in more copies of the reverse locus, which was beneficial to the origin of the reverse locus copy. However, the reverse locus gene has always shown high methylation level, which may be due to a defense mechanism, which is to prevent the reverse locus gene from being eliminated prematurely under the action of selection pressure because of individual deleterious mutations. The hypermethylation of the reverse locus gene can increase the mutation rate of the gene, which is more favorable to the accumulation of more mutations in a short period of time. Under the action of natural selection, individual favorable mutations contribute to their survival. The DNA methylation of the parent gene and the reverse locus gene in the gene body was affected by the selection pressure. The level of DNA methylation in the promoter region changes with the evolution time and regulates the expression of the reverse locus gene. In conclusion, on the one hand, the reverse locus event is beneficial to the formation of new genes in pigs, and on the other hand, it is discussed that DNA methylation plays an important role in the origin, evolution and survival of porcine reverse locus gene.
【学位授予单位】：华中农业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S828

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