Genetic characterization of horse bone excavated from the Kwakji archaeological site, Jeju, Korea.

We determined the nucleotide sequences of the hypervariable D-loop region of mitochondrial DNA (mtDNA) from horse bone (humerus, A.D. 700 to A.D. 800) that was excavated from the Kwakji archaeological site, Jeju, Korea. We compared them with ones from extant horses. We designed three pairs of oligonucleotide primers from the tRNA-Thr and tRNA-Phe gene regions of mtDNA that are highly conserved among many other animal species. We cloned 232, 336, and 644 bp from the horse bone in order to determine the mtDNA D-loop sequence. The sequence was 1,124 bp long; the middle contained 19 tandem repeats of an 8-bp sequence (TGTGCACC) that is specific to equines. The mtDNA D-loop region contained each base (total number, percentage of total) as follows: A (317, 28.20%), C (336, 29.89%), G (169, 15.04%), and T (302, 26.87%). This sequence, like those of other horse populations, was AT rich. Sequence divergence was the lowest (1.71%) between the ancient horse bone and that of the Thoroughbred horse 1. The neighbor-joining and strict consensus tree of three of the most parsimonious trees also suggested that the ancient bone was considerably unrelated to native Jeju horses. The molecular phylogenetic characteristics of the horse bone that was excavated from the Kwakji archaeological site (Jeju, Korea) showed that some horse breeds may have existed on Jeju Island, Korea before Mongolian horses were introduced. The horse bone that was excavated from the Kwakji archaeological site may aid future research on the origin and ancestry of native Jeju horses.