Combined deletion of Sik2 and Sik3 in osteoblasts and osteocytes led to a dramatic increase in bone mass that closely resembled the skeletal and molecular phenotypes observed when these bone cells express a constitutively active PTH1R that causes Jansen's metaphyseal chondrodysplasia.
Increased PTHrP action with hypercalcemia may be seen in the benign disease Jansen's metaphyseal chondrodysplasia due to a gain-of-function mutation in PTHR1.
Several are discussed in detail, including osteogenesis imperfecta and type I collagen mutations, Jansen metaphyseal chondrodysplasia and parathyroid hormone/parathyroid hormone-related protein receptor mutation, and chondrodysplasias caused by fibroblast growth factor receptor 3 mutations.