Cover photograph (Copyright © 2012, American Society for Microbiology. All Rights Reserved.): Progerin expression disrupts the nucleocytoplasmic gradient of the Ran GTPase. Shown are HeLa cells transfected with the mutant form of lamin A (progerin) that is expressed in patients with the premature aging disease Hutchinson-Gilford progeria syndrome. Progerin (red) and endogenous Ran (green) were detected by immunofluorescence microscopy. Under steady-state conditions Ran is predominantly nuclear, but in response to progerin the nuclear concentration of Ran is reduced, resulting in nuclear transport defects of certain proteins. The photo was provided by Sutirtha Datta and Bryce Paschal. (See related article in August 2011, vol. 31, no. 16, p. 3378.)
