Evolutionary history of the mtDNA 9-bp deletion in Chinese populations andits relevance to the peopling of east and southeast Asia

In total, 1218 Chinese from twelve ethnic groups and nine Han geographic gr oups were screened for the mtDNA 9-bp deletion motif. The frequency of the 9-bp deletion in all samples was 14.7% but ranged from 0% to 32% in the var ious ethnic groups. Three individuals had a triplication of the 9-bp segmen t. Phylogenetic and demographic analyses of the mtDNA hypervariable segment 1 (HVS1) sequences suggest that the 9-bp deletion occurred more than once in China. The majority of the Chinese deletion:haplotypes (about 90%) have a common origin as a mutational event following an initial expansion of mod em humans in eastern Asia. Other deletion haplotypes and the three haplotyp es with a 9-bp triplication may have arisen independently in the Chinese, p resumably by replication error. HVS1 haplotype analysis suggests two possib le migration routes of the 9-bp deletion in east and southeast Asia. Both m igrations originated in China with one route leading to the Pacific Islands via Taiwan, the other to southeast Asia and possibly the Nicobar Islands. Along both routes of peopling, a decrease in HVS1 diversity of the mtDNA ha plotypes is observed. The "Polynesian motif (16217T/C, 16247A/G, and 16261C /T)" and the 16140T/C, 16266C/A, or C/G polymorphisms appear specific to ea ch migration route.