Microsatellite instability in mononuclear cells from non-tumorigenetic human tonsils and its forensic applications

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Microsatellites consisted of tandem repeated sequence motifs of 1 to 6 nucleotides in length are highly polymorphism and scattered more or less randomly throughout the genome. The use of polymorphism microsatellite DNA sequences has become extremely important in genetic mapping studies and in the diagnosis of human genetic diseases. Microsatellite instability (MSI) has been reported to be a landmark of some tumors of the colon and rectum and is characterized by small deletions or expansions within short tandem repeats in tumor DNA as compared with matching normal DNA.In this project, we have tried to find the presence of MSI in healthy individuals and to examine the application of forensic cases. TH01 locus was selected as a microsatellite and determined at the mononuclear cells isolated from tonsils. Seminested PCR was performed to determine TH01 types using single cells. One hundred and seventy-eight out of 450 cells could be typed (39.6%) and the type of only 1 cell (0.56%) was mutated. This result indicates that a microsatellite alteration at TH01 locus may be observed in the cells proliferated vigorously in tissues. However, there is little probability that microsatellite typing will be incorrect using a DNA template that includes mutated DNA at 0.56% of cells.