Contents

02 September 2015
Vol 7, Issue 303

About The Cover

Cover image expansion

ONLINE COVER When Muscle Turns to Bone. Shown is the skeleton of a patient with the disease fibrodysplasia ossificans progressiva, a fatal genetic disorder caused by mutations in the ACVR1 receptor in which muscle and soft tissue turn to bone. By engineering a new mouse model in which expression of mutant ACVR1 is precisely controlled, Hatsell and colleagues discovered that activin A, a growth factor that normally blocks ACVR1 activity, aberrantly activated the mutant receptor driving bone formation. Treating the mice with a human antibody directed against activin A arrested bone formation for up to 6 weeks suggesting that this may be a new therapeutic approach for treating this tragic disease. [CREDIT: THE SKELETON OF HARRY EASTLACK, FIBODYSPLASIA OSSIFICANS PROGRESSIVA (FOP) EVI NUMEN, 2011, THE MÜTTER MUSEUM OF THE COLLEGE OF PHYSICIANS OF PHILADELPHIA]