These mice were born normal but Col1 deletion in Fsp1-lineage cells led to the occurrence of spontaneous Osteogenesis Imperfecta (OI) symptoms in adult Col1a1fspKO mice, which was analogous to the previous observations employing systemic transgenic mice harboring dominant mutations of Col1a1 and Col1a26,12,14,15,38,39. This evidence concerns the gene COL1A1 and osteogenesis imperfecta.