ACVR1 and fibrodysplasia ossificans progressiva: Interestingly, while ACVR1 mutations suffice to increase proliferation of immortalized normal human astrocytes (Buczkowicz et al. 2014), mutations in the identical amino acids are found in the germline of individuals with the autosomal dominant congenital childhood disorder FOP (fibrodysplasia ossificans progressiva), who have no evidence of cancer predisposition (Jones and Baker 2014; Taylor et al. 2014b).