A rapid mtDNA assay of 22 SNPs in one multiplex reaction increases the power of forensic testing in European Caucasians

We have developed a multiplex mitochondrial (mtDNA) assay of 21 coding region single nucleotide polymorphisms (SNPs) and one control region SNP outside hypervariable region 1 (HVR1) and hypervariable region 2 (HVR2) that can be amplified in a single reverse touchdown polymerase chain reaction. Single base extension using the SNaPshot technique is also carried out as one multiplex. Besides the nine major European haplogroups (i.e. H, I, J, K, T, U, V, W, and X), 16 additional subclades (i.e. N1, X2, X2b, U2′-4/7′-9′, J/T, J1, J1c, HV, H1, H1a1, H1c, H3, H4, H6a, H7a H10) can be detected and classified into a phylogenetic mtDNA tree. By analyzing 130 Caucasoid samples from Germany, 36 different haplotypes were found resulting in a power of discrimination of 93.2%. Although 49% of all samples belonged to superhaplogroup H, the most common haplotype, i.e., haplogroup-specific SNPs plus haplogroup unspecific SNPs, had a frequency of only 18%. This assay is applicable for high-throughput mtDNA analysis and forensic mass screening. It will give additional information to the common control region sequencing of HVR1 and HVR2.