Studies On The Evolutionary Genetic Mechanism Of The Skeletal System In Humans And Chinese Ornamental Chicken Based On The Population Genomics Approach

In biology, the definition of the skeletal system is a living system which provides life support for animals. The skeletal system provides many important functions, for example, it provides us mechanical support. In addition, it plays an important role in protecting vital organs, and provides a microenvironment for hematopoiesis. It is also a depot for calcium and other minerals. Modern human populations exhibit substantial phenotypic variation as evidenced by body mass, height and craniofacial differences shaped by the skeletal system. In addition, the different strains of domestic animals also exhibit substantial phenotypic variation. The phenotypic variation is a good material to study on biological evolution. The coming of genomic era with the application of next generation sequencing leads to the emergence of a large amount of sequencing data. The flood of sequencing data and analytical methods for detecting selection offer unprecedented opportunities to study the evolutionary molecular mechanisms of the phenotypic, facilitate my study on biological problems, such as the evolutionary mechanism of adaptation of special characters and the origin of species and so on. In this thesis, I choose humans and Chinese ornamental chickens as the research objects to explore the mechanisms of evolution of the skeletal system based on the methods of population genetics.In the second section, I use more than 130 skeletal genes from prior studies to investigate the population differentiation pattern of skeletal genes in modern humans based on the 1,000 Genomes Phase I data. The analytical methods based on different theoretical, such as FST, Tajima’s D, iHS are used to detect selection. The results support an earlier study that higher population differentiation of human skeletal genes exists between Africans and non-Africans. In addition, my further analysis indicates skeletal genes of three non-African populations have suffered positive selection after the out-of-Africa events. Positive selection has also operated on the skeletal genes in the American populations recently, but positive selection has not operated on skeletal genes in the African, European, Asian populations recently. Since spreading to all over the world, people are in different environments, which results in the evolutionary inconsistencies of modern populations.In the third section, the phenotypic variation of chinese ornamental chickens is a good material to study the rapid evolution of skeletal system. I choose chickens of small body size as my study objects, and then combined sequencing data of these samples and published genome data and use population genetics to find out genes associated with skeletal system, which show significantly higher population differentiation between different body size strains. To further identify the skeletal gene, we do PCR amplification and sequence for this gene in different body size strains. We found linkage disequilibrium SNPs sites. To further explore this potential target of selection, a medianjoining(MJ) network was constructed to describe the evolutionary relationships between the 8 haplotypes in exon 1 and the 2Kb region of 5’UTR upstream of BMP 10 gene, which were inferred from the 28 SNPs. There is a high degree of divergence of haplotype composition between small body size chickens and other large body size chickens. Previous study about this genes showed that overexpression of this gene in mice can result in heart weight, body weight becoming smaller. We validate this gene in the zebra fish. As expected, the body size of zebra fish becomes significant smaller due to overexpression of this gene. Now biotech company doing some functional experiments, such as Dual-Luciferase reporter assay system and EMAS-electrophoretic mobility shift assay. These results show that BMP 10 gene plays a vital role on small body size in chickens. The research provided the certain information for studying population history of domestic animals. Also, the above results provide basic information for the biochemical genetic survey of Chinese ornamental chicken populations and artificial breeding of Chinese ornamental chickens.