RUNX2 and osteoporosis: They also observed decreased osteoblast differentiation and severe osteoporosis in mice lacking the CaN catalytic subunit, and after TAT sequence was used to introduce CnA into mouse embryonic osteoblast precursor cells (MC3T3‐E1 cells), the expression of osteogenic marker genes RUNX2, ALP, bone sialoprotein (BSP) and OCN increased significantly, so Sun et al.50concluded that osteoporosis in CaN‐deficient mice is caused by defects in bone formation.