Transgenic mice for studying fibrous dysplasia of bone, McCune-Albright Syndrome, and tumors caused by activating GNAS mutations.
Category: Rare Bone Diseases
Poster Sessions, Presentation Number: LB-SU0375
Session: Late-Breaking Posters II
Sunday, September 18, 2016 12:30 PM - 2:30 PM, Georgia World Congress Center, ASBMR Discovery Hall - Expo Hall A1
* Vijayram Reddy Malladi, Endocrine Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School , Yan Zhu, Endocrine Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, olta tafaj, Endocrine Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Murat Bastepe, Endocrine Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School
GNAS encodes the alpha-subunit of the heterotrimeric stimulatory G protein (Gsα), which mediates the actions of many endogenous molecules through generation of cAMP. Somatic GNAS mutations that cause constitutive Gsα activity are found in many tumors (gsp oncogene) and cause fibrous dysplasia of bone (FD), a disorder characterized by aberrant differentiation of bone marrow stromal cells (BMSCs). The same mutations also lead to McCune-Albright Syndrome (MAS), in which FD co-exists with hyperpigmented skin lesions and overactive endocrine organs. Mechanisms governing FD and MAS phenotypes are poorly defined. To generate a mouse model for studying these disorders, as well as gsp+ tumors, we developed transgenic mice in which cDNA encoding a HA-tagged, constitutively active Gsα mutant (Gsα-R201H) is expressed conditionally upon Cre recombinase activity (caGsα Tg mice). The transgene also contains a LacZ reporter downstream of the Gsα-R201H cDNA. Adeno-Cre transduced BMSCs from the caGsα Tg mice showed significantly higher baseline cAMP levels than in non-transduced or adeno-YFP (control) transduced cells and demonstrated positive X-gal staining. Double-mutant offspring from crosses between caGsα Tg and Prx1-Cre mice displayed short limbs and underdeveloped craniofacial bones, consistent with the expression profile of Prx1 and the role of Gsα/cAMP signaling in endochondral bone formation. In BMSCs from caGsα Tg;Prx1-Cre mice, the expression level of c-fos mRNA, a target of Gsα/cAMP signaling, was increased by 3.5-fold compared to that in control BMSCs. Moreover, expression of the transgene could be induced postnatally, as judged by positive X-gal staining in various tissues, by injecting tamoxifen into double-mutant offspring from caGsα Tg and CAGG-CreERTM crosses. These findings indicate that our mice express the Gsα-R201H transgene in a conditional manner. This mouse model will be highly valuable for investigating the molecular mechanisms underlying FD/MAS, as well as the oncogenic mechanisms in gsp+ tumors.
* Presenting Authors(s):
Vijayram Reddy Malladi, Endocrine Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School