Abstract: There is provided a mutation complex including: a BMPR2-E376K mutant in which an amino acid at position 376 of BMPR2 gene encoding a bone morphogenetic protein type 2 receptor (BMPR2) has mutated from glutamic acid (E) to lysine (K); and an ACVR1-R206H mutant in which an amino acid at position 206 of ACVR1 gene encoding an activin A type I receptor (ACVR1) has mutated from arginine (R) to histidine (H). There are also provided induced pluripotent stem cells reprogrammed from cells including the BMPR2-E376K mutant in which an amino acid at position 376 of BMPR2 gene encoding a bone morphogenetic protein type 2 receptor (BMPR2) has mutated from glutamic acid (E) to lysine (K).

Abstract: Disclosed is a technique for identifying a mutation of a particular gene as a new case of a FOP-like phenotype, in addition to the existing ACVR1-R206H mutation known as a cause of FOP and utilizing the identified mutation in the bone disease treatment through osteogenic differentiation. There is provided a bone morphogenetic protein type 2 receptor (BMPR2)-E376K mutant in which the 376th amino acid glutamic acid (E) is mutated into lysine (K) in the BMPR2 gene encoding BMPR2.