Using Minisequencing Technology for Analysing Genetic Variation in DNA and RNA

Abstract: In this thesis, the four-color fluorescence tag-microarray minisequencing system pioneered by our group was further developed and applied for analysing genetic variation in human DNA and RNA. A SNP marker panel representing different chromosomal regions was established and used for identification of informative SNP markers for monitoring chimerism after stem cell transplantation (SCT). The success of SCT was monitored by measuring the allelic ratios of informative SNPs in follow-up samples from nine patients with leukaemia. The results agreed with data obtained using microsatellite markers. Further the same SNP marker panel was used for evaluation of two whole genome amplification methods, primer extension preamplification (PEP) and multiple displacement amplification (MDA) in comparison with genomic DNA with respect to SNP genotyping success and accuracy in tag-array minisequencing. Identical results were obtained from MDA products and genomic DNA.The tag-microarray minisequencing system was also established for multiplexed quantification of imbalanced expression of SNP alleles. Two endothelial cell lines and a panel of ten coding SNPs in five genes were used as model system. Six heterozygous SNPs were genotyped in RNA (cDNA) from the cell lines. Comparison of the relative amounts of the SNPs alleles in cDNA to heterozygote SNPs in genomic DNA displayed four SNPs with significant imbalanced expression between the SNP alleles. Finally, the tag-array minisequencing system was modified for detection of splice variants in mRNA from five leukaemia cell lines. A panel of 20 cancer-related genes with 74 alternatively splice variants was screened. Over half of the splice variants were detected in the cell lines, and similar alternative splicing patterns were observed in each cell line. The results were verified by size analysis of the PCR product subjected to the minisequencing primer extension reaction. The data from both methods agreed well, evidencing for a high sensitivity of our system.