Generation and characterization of murine models to study the molecular mechanisms of G protein signaling in the thyroid and their role in thyroid diseases

促甲状腺激素受体(TSHR)的结构性激活突变通过G蛋白Gs的永久激活导致甲状腺激素的不受控制的释放，从而导致人类非自身免疫性甲状腺功能亢进症(NAH)。在极少数情况下，一些TSHR变异体也激活GQ/11。这种G蛋白在NAH过程中激活的详细功能结果尚不清楚。TSHR的结构性激活突变是非自身免疫性甲状腺功能亢进症的主要分子病因，在毒性甲状腺结节(TTN)、散发性非自身免疫性甲状腺功能亢进症(SCNAH)和常见的非自身免疫性甲状腺功能亢进症(FNAH)患者中都有检测到。TSHR突变的功能鉴定仅通过异种细胞系统的体外实验进行，这阻碍了体内条件下NAH的生理和分子遗传学研究。在体内研究激活的TSHR突变将显示对NAH的发展和表现的影响，并将允许与体外方法获得的结果进行比较。因此，我们建立了一个激活TSHR突变D633H的小鼠模型，该突变独立于天然配体促甲状腺激素激活两个信号级联(Gs和GQ/11)。该模型将能够研究不同信号通路在甲状腺功能中的作用，确定基因表达谱的变化，不同G蛋白在肿瘤发生中的影响，碘供应的影响以及甲状腺外TSHR表达的研究。此外，它代表了一个体内模型来研究新发现的小分子配体与目前用于治疗NAH的抗甲状腺药物相比具有反向激动性的TSHR的潜力。

Constitutively activating mutations of the thyroid stimulating hormone receptor (TSHR) lead to nonautoimmune hyperthyroidism (NAH) in humans through a permanent activation of the G protein Gs resulting in an uncontrolled release of thyroid hormones. In rare cases some TSHR variants also activate Gq/11. The detailed functional outcome of this G protein activation in the course of NAH remains unclear. Constitutively activating mutations of the TSHR are the major molecular cause for nonautoimmune hyperthyroidism and were detected in patients with toxic thyroid nodules (TTNs), in sporadic nonautoimmune hyperthyroidism (SCNAH) and familiar nonautoimmune hyperthyroidism (FNAH) Functional identification of TSHR mutations as the molecular cause for this disease is exclusively carried out by in vitro experiments in heterologous cell systems, which hampers the physiological and molecular genetic investigation of NAH under in vivo conditions. Studying an activating TSHR mutation in vivo would show the impact for the development and manifestation of NAH and would allow a comparison to findings obtained by in vitro approaches. Therefore, we generated a mouse model with activating TSHR mutation D633H, which activates both signaling cascades (Gs and Gq/11) independently from the natural ligand thyrotropin. This model will enable the investigation of the contribution of different signaling pathways in thyroid function, the determination of changes in genetic expression profiles, the impact of different G proteins in cancerogenesis, the impact of iodine supply and the investigation of extra-thyroidal TSHR expression. Further, it represents an in vivo model to investigate the potential of newly identified small molecular ligands for the TSHR with inverse agonistic properties over currently used anti-thyroid drugs for the treatment of NAH.