Mice expressing the engineered Gs-GPCR Rs1 in osteoblastic cells using the Collagen I 2.3 kb promoter fragment [ColI(2.3)+/Rs1+ mice] develop bone phenotypes that strongly resemble fibrous dysplasia of the bone, including increased trabecular bone formation, cortical erosions, and disorganized bone formation with rapid turnover and remodeling [26]. Here, RS1 is linked to fibrous dysplasia.