ACVR1 and brain disorder: Out of these three receptors, we first focused on ACVR1, a Type I receptor that is expressed in a variety of cell types and plays key roles in bone and brain diseases (Agarwal et al., 2017; Shore et al., 2006; Valer et al., 2019), and asked whether reducing its expression could make ligand responses in NMuMG cells more similar to those of mESCs.