骨纤维结构不良（FD）是临床最为常见的良性骨病，多有口腔颌面部显著表征，缺乏有效治疗手段；其相关疾病McCune-Albright综合症于2018年被列入中国《第一批罕见病目录》。申请人证实(PNAS 2018年)：Gαs激活型突变是FD发生、维持的充分且必要条件，还发现Gαs下游效应分子蛋白激酶A（PKA）处于高度磷酸化激活状态。但尚未阐明，Gαs激活型突变作用是否依赖PKA的激活？靶向阻断PKA能否缓解FD？为此，拟首先通过体外构建PKA激活型突变质粒（PkacaW197R），通过体外实验验证PKA对干细胞成骨、破骨分化的影响；然后，构建（1）可诱导型、组织特异性PKA激活和（2）Gαs-cAMP激活、特异性阻断PKA的转基因小鼠模型，验证FD对PKA的依赖性，探究PKA靶向治疗效果；最后，研究PKA介导早期成骨分化和骨重建的分子机制，为阐明FD的发病机制及靶向治疗提供新思路。

Fibrous dysplasia (FD) is one of the most common benign bone disease, with high prevalence of craniofacial manifestation. Currently there is no cure for this disease. Its related diseases, McCune-Albright syndrome, has been included into the First catalogue of rare diseases in 2018. The applicant demonstrated (PNAS 2018) that the active Gαs mutant is sufficient and necessary for FD initiation and maintenance. Also, the applicant found protein kinase A (PKA), an important downstream effective molecule of Gαs, was significantly phosphorylated. However, it’s still not clear that whether FD initiates in a PKA dependent fashion? And how PKA made it in molecular level and whether fibrous dysplasia rely strongly on activation of PKA are still wait to be answered. In this project, we first plan to create PKA activating mutant plasmid (PkacaW197R) in vitro, which will be used to study the osteogenic and osteoclastogenic induction effects in vitro. Next, we plan to generate: (1) inducible and tissue specific activating PKA and (2) PKA inhibition while Gαs-cAMP activation transgenic mouse models, to study whether FD is PKA dependent and explore the target therapeutic effect of PKA for FD. Finally, we will study the molecular mechanisms underlying early bone formation and bone remodeling induced by PKA, to shed a new light on the pathogenesis of FD and PKA targeted therapy.