This was supported by COL1A1 to COL1A2 mRNA ratio findings in human OI cell models, including fibroblasts and induced mesenchymal stem cells, as well as in induced pluripotent and mesenchymal stem cell models that were edited to carry a heterozygous COL1A1 allele. The gene discussed is COL1A1; the disease is osteogenesis imperfecta.