Figure 2.

Frequency of the HTT haplotype B2 in the populations of the 1000 Genomes Project

The African B2 haplotype was defined by SNPs rs2857936-rs762855-rs4690073 as described by Baine et al.²³ The haplotype frequencies were obtained using the LDhap tool from the LDlink suite (ldlink.nci.nih.gov).²⁸ Haplotype B2 was shown to have the highest frequencies among the African and African ancestry populations, ranging between 6.6% and 9.9%. Outside of the continental African populations, Puerto Rico (American) had the highest frequency of haplotype B2 (3.4%), followed by the five East Asian populations (range from 0.5% to 1.0%). The Columbian (American), Utah residents (European), and Sri Lankan (South Asian) populations had low frequencies (0.5%), and B2 was not detected in the rest of the populations analyzed. The results were comparable with the frequency of B2 in the African ancestry non-disease alleles included in this study. This indicates that, although this analysis was only conducted in non-disease alleles, haplotype B2 may be of an African origin and an African-specific haplotype.