Increased efficiency of cellular retinoic acid catabolism by the minor CYP26B1 variant. Plasmid constructs containing the major or minor variant of rs2241057 were transfected into COS-1 cells and THP-1 macrophagelike cells, and levels of the 55-kDa CYP26B1 were determined by Western blot in COS-1 cells (A). Cellular levels of supplemented (3H)atRA were measured by HPLC in COS-1 cells (B) and THP-1 cells (C). Values are relative to protein concentration and SEAP activity, and shown as mean ± SD. **P < 0.01, ***P < 0.001.