PPARG and osteopetrosis: This is important since PPAR-γ plays an essential role in osteoclastogenesis: mice in which PPAR-γ was selectively ablated in osteoclasts (using CRISPR/Cas9) showed osteopetrosis i.e. an abnormal increases in bone mass (Wan et al., 2007), while PPAR-γ promotes osteoclast differentiation through up-regulation of c-fos, a key regulator of RANK/RANKL signalling (Wan et al., 2007).