Application Of Genome-Wide Association Study In Mapping Of Susceptibility Genes In High Myopia And Exome Sequencing In Identifying Genes Responsible For Transposition Of Great Arteries

Genome-wide association studies (GWAS) and exome sequencing are powerful tools for disease gene mapping. In this thesis, we try to use GWAS to identify susceptibility genes of high-grade myopia (HM) in Chinese Han, and locate causal genes of transforming of great artery (TGA) through exome-sequencing a discordant twin pair.HM refers to extreme myopia with refraction error less than-6.00D or axial length higher than26mm. Although epidemiology analysis has proved the important role of genetic factors, the related genes of HM are remaining unclear. In order to identify loci contributing to HM susceptibility in Chinese Han population, we adopted a DNA pooling based GWA study. Before GWAS began, we first used476HM patients and275none myopia controls to perform candidate gene association analysis on MIR100HG and BLID gene region, which have been identified as susceptibility loci for HM in Japanese. With no evidence in this region showing association with HM (p>0.05, on all tag SNPs), we then carried out pooling GWAS on504patients and276controls. After verification by individual genotyping, we obtained9loci associated with HM. In consideration of biological function, we chose rs10889602, which locates in the intron of PDE4B, as candidate susceptibility SNP locus (pooling p=13%×10-6; individual verification p=0.0198). In replication study, we demonstrated rs10889602truly associated with HM in Han Chinese (pmeta=3.72×10-3), using two different Chinese Han cohorts with1,606cases and1,509controls in total. Furthermore, functional studies from our collaborator proved that inhibition of PDE4B would lead to myopia in guinea pigs.TGA is a kind of cyanotic congenital heart diseases, and its pathogenesis remains largely unknown. Aiming to test the role of genetic factors on formation of TGA, we sequenced whole exomes of a monozygotic discordant twin pair with one with TGA and the other staying normal. By high throughput sequencing, we identified variations at49SNP loci between this twin pair. However, none was proved by mass-array genotyping, and all seemed to be sequencing error. Moreover, indel and CNV analysis also showed no evidence of difference between the twins. After mutation analysis, we identified a missense mutation (G1437R) in NOTCH1gene, which plays an important role in balance development and has been linked with TOF (Tetralogy of Fallot) and AS (Aortic Stenosis) in previous studies. Although we cannot prove the roles of somatic mutations in the appearance of discordant phenotypes of this twin pair, the results still indicate that genetic factors play important roles in TGA formation.