REEP6 and Stargardt disease: These genes include 3 PR genes, Reep6 (receptor accessory protein 6), Slc24a1 (retinal rod Na+/Ca+/K + exchanger), and Stargardt disease gene, Abca4. However, Lehmann and coworkers found that Slc24a1 is highly expressed by the mouse RPE cluster [33], and expression of Abca4 by RPE is now established [52].