MtDNA Sequence Analysis Using Capillary Electrophoresis and Its Application to the Analysis of MtDNA in Hair

A procedure for the analysis of mitochondrial DNA (mtDNA) using capillary electrophoresis instead of former gel-based methods is described. The procedure requires less manual manipulation in terms of electrophoresis and, therefore, reduces the chance of either human- or gel-related failures. Thus, the method is suitable for performing mtDNA typing from limited amounts of forensic samples.   We also performed mtDNA typing of hair samples using this method, and were successful in typing from both hair roots and hair shafts as well as saliva and nail samples. The amount of PCR product indicated that the amount of mtDNA in the tip side of the hair shaft was less than that in the root side. However, one hair sample showed equal amounts of PCR products in both the tip and the root side. For the analysis of a sample derived from an individual with heteroplasmic mtDNA, the proportions of heteroplasmy from the saliva and nail samples were different from those from hair samples. For analyses of hairs from the same individual, each region of the hair showed different proportions of heteroplasmy and the results indicated the possibility of the different sequences in the same hair sample. Therefore, mtDNA analysis of hair samples will require additional investigation of procedures for heteroplasmic mtDNA. These results strongly suggest that the application of the developed method for hair samples will require careful treatment of the samples and a rigorous analysis of the results.