Dissection Of Hereditary Constitution Of Wild-Derived Chr1 CSS Mice By STR

At present, mouse genetics has entered a stage of dissecting complex traits through genetic approaches, which requires animal models with rich genetic diversity. There are some shortages in terms of the genetic diversity of existing laboratory mouse strains. The subspecific origin of the established strains is strictly limited, which was mainly derived from the Mus musculus domesticus, accounting for more than 90% of the genome for laboratory mice. Whereas the Mus.m.musculus and Mus.m.castaneus accounted for about 10% altogether. Recent studies have shown that the genetic diversity of wild mouse (Mus musculus) is far more extensive than the laboratory mice which is suitable for genetic studies of complex traits and can be important genetic resources. Early studies have shown that the M. m. musculus subspecies are mainly distributed in northern China Mus musculus, and the Mus. M. castaneus in southern China. Therefore the Chinese taxa are extremely important to complement the genetic diversity of the laboratory stocks.The thesis project is an essential part of the plan to build the population of Chrl substitution strains, which has been implemented for 2 years in the host laboratory. The conventional chromosome substitution strains strongly facilitate the progress of genetic dissection of complex diseases with mouse models. However this special tool, CS mice are restricted to initial mapping of quantitative trait loci or QTLs, and can not cannot solve the fine mapping problem, which is the current bottle neck for quantitative genetics in mice. This is resulted from the facts that the laboratory mice lack in genetic, and the conventional CS strategy still depends on recombination events at repeated crosses, a time consuming and labor intensive task hindering the progress of quantitative mouse genetics. On the other hand, the wild mice have highly polymorphic genomes, and one gene locus has far more alleles in comparison with the laboratory mice. More importantly, the wild mice harbor historical recombination events and the linkage disequilibrium is more complex and favorable for polygenetic studies. Therefore, by constructing the chromosome substitution strains with donors from the wild mice, the issue of genetic diversity of inbred mice can be well addressed, and the new CS strains will provide direct and convenient resources for identification of genes underlying complex diseases and traits.Prior to the construction of Chrl CS strains, genetic diversity of the wild donors need to known. Our group sampled 25 wild donors from 9 provinces. This study elucidated the genetic diversity of the donor chromosomes, by genotyping twenty microsatellite DNA markers (STR) on Chrl, which is an essential step for transmission of the wild donor chromosomes into the recipient background, the genome of C57BL/6J. The results of this study are summarized as follows:1.20 STR loci of Chrl were selected and analyzed, using multiplexed tandem PCR (MT-PCR) technology to detect the diversity of wild mice captured in different regions of China. The selected 20 STR loci and optimized reaction of MT-PCR is the primary step for construction of Chrl substitution strains, and in addition, the well tested technology can also be applied to investigate population genetics of wild mice.2.341 alleles were found in the 20 STR loci, of which the largest number of allelic variants was 24 for D1Mit218, and 9 alleles were found for locus D1Mit254 was the least in allelic variants count. Wild mice had number of alleles of 15.4±3.5 for 20 STR loci, while the laboratory mcie had 5.3±1.0 alleles.3. The wild had higher level of average expected heterozygosity 0.886±0.04 for 20 STR loci than the laboratory derived hybrids 0.727±0.112, (t-test, P=1.04×10-6).4. In wild population the G-W stat of 20 STR loci were 0.781±0.132, significantly higher than those of laboratory mice whose G-W stat were 0.377±0.184 (t-test, P=1.76×10-8).5. In this study, the average genetic distance of the laboratory mice groups and the wild mice groups are 0.152±0.064 and 0.133±0.021. As a result long-term unnatural breeding, genetic drift, large genetic distance between individuals can be observed in the laboratory strains of mice, which is not sufficient to explain the laboratory strains for high genetic diversity.6. According to the cluster analysis between wild mice and laboratory mice, they were clearly clustered into two categories. However due to the sampling bias, for example some locality only had one mouse, genetic relationship between different mice was not determined.Through the thesis project, wild mice (Mus musculus) were revealed to be of extensive polymorphism, which is a necessary complementary to the laboratory mice. The wild resources are essential tools for genetic dissection of complex traits. This study provided theoretical evidence and empirical basis for further use of genetic resources of wild mice in China.