FIGURE 9.

Phylogeny of human and mouse Oats and Usts. Slc22a6 (Oat1) and Slc22a8 (Oat3), both of which exist in mouse and human, appear to have arisen from tandem duplication of an Oat ancestral gene. Multiple rounds of duplication of the Ust (unknown substrate transporter) ancestral gene are proposed to have led to several Ust-like genes by the time of human and mouse divergence. After this, certain mouse Usts are proposed to have undergone further duplication to generate other mouse-specific Ust genes. Some Usts exist in human while others exist in mouse, but no orthologous Usts exist in both species. [Modified from Wu et al. (283).]