Position of the three candidate causal mutations within ABCB1, showing the position of the three new candidate variants in high LD with 3435C>T. In the boxes are the two regions further investigated by phylogenetic shadowing. Plots of cumulative nucleotide divergence were generated using the eShadow tool by amplifying the region surrounding IVS 25+3050 G>T (A) and 3435C>T (B) in 17 and 15 primate species, respectively. Orange shading indicates the region of significant conservation; the horizontal red bar at nucleotides 715–921 of the alignment in B indicates the position of exon 26. The position of the three intronic sites is marked by a vertical dashed line: IVS 25+3050 G>T at nucleotide 710 (A), and IVS 25+5231 T>C, 3435C>T, and IVS 26+80 T>C sites at 184, 867, and 1001 bp of the alignment (B).