SOX9 and Osteochondroma: The enchondromas and osteochondromas found in old SHP2KOBglap mice were primarily comprised of R26ZSG+ (Bglap+) cells that also expressed Sox9, Col2α1, and Acan (Figs 6b, c and S8), mimicking the features of human MC in which somatic PTPN11 LOF mutations and enhanced chondrocytic gene expression have been identified.39,40 This notion supports the tumor suppressor role of SHP2 in cartilage39,40 and suggests that BGLAP may play a role in growth plate cartilage during aging.