Contents

11 October 2013
Vol 342, Issue 6155

About The Cover

Cover image expansion

COVER False-colored scanning electron micrograph of erythrocytes (diameter ~7 micrometers). Sickle cell disease results from an inherited defect of adult hemoglobin, the oxygen-carrying metalloprotein constituent of erythrocytes. Common genetic variation associated with sickle cell disease severity modulates an adult-stage erythroid enhancer element of the BCL11A gene. Disruption of this element could ameliorate the disease by reestablishing expression of fetal hemoglobin. See pages 206 and 253. Image: Dennis Kunkel Microscopy, Inc./Visuals Unlimited, Inc.