Stem-cell promise

Patient-specific iPS (induced pluripotent stem) cells are seen as key to modelling genetic disorders and developing new treatments for them. Now iPS cell lines have been generated by nuclear reprogramming from patients with ‘LEOPARD’ syndrome, a rare developmental disorder characterized by skin lesions, heart abnormalities and deafness. Cardio myocytes derived from the resulting LEOPARD iPS cells have hypertrophic properties resembling those typical of the disease — cardiac hypertrophy occurs in 90% of children with the syndrome. The reprogrammed cells feature extensive alterations in various signal transduction pathway components, including RAS–MAPK, some previously described in association with cardiac hypertrophy. Using these cell lines, together with robust differentiation protocols, it may be possible to identify compounds that reverse diseased cellular phenotypes. The cover depicts a cardiac troponin T-positive cardiomyocyte derived from a LEOPARD syndrome iPS cell. [Letter p. 808]