In vivo Analysis of RORgamma mediated Functions

描述(由申请人提供)：细胞凋亡是生物体内发育和维持内环境平衡所必需的基本生理过程。原癌基因Bcl2是细胞凋亡信号转导通路的重要调控因子。Bcl2的表达改变与肿瘤的发病机制和化疗药物耐药有关，其原因是诱导细胞凋亡失败。 细胞凋亡用于消除大多数发育中的胸腺细胞，这些细胞要么不被主要组织相容性复合体识别，要么不具有自我反应能力。通过基因打靶，我们已经证明了核受体家族成员维甲酸相关孤儿受体γ(RORGamma)在胸腺细胞和淋巴结的发育中起着关键作用。在没有RORGamma的情况下，胸腺细胞经历快速的凋亡和不受调控地进入细胞周期的S阶段。相应地，RORGamma缺乏的胸腺细胞具有显著较低的抗细胞凋亡的Bclxl和细胞周期抑制物p27kip1的水平。过表达Bclxl在RORGamma缺乏的胸腺细胞中恢复存活和细胞周期进展。RORGamma基因缺失的小鼠不能发育出淋巴结，可能是由于早期胚胎阶段缺乏淋巴结祖细胞所致。我们假设，RORGamma调节胸腺细胞和淋巴结发育所需的关键生存和细胞周期分子的表达。我们建议研究RORGamma介导转录的分子机制及其在胸腺细胞体内成熟中的作用。此外，我们还将研究RORGamma如何调节外周淋巴器官的发育。这些研究将深入了解核受体在体内T细胞和次级淋巴组织发育中的调节作用。

DESCRIPTION (provided by applicant): Apoptosis is an essential physiological process required for the development and maintenance of homeostasis in an organism. The Bcl-2 proto-oncogene is a critical regulator of the apoptotic signaling pathways. Altered expression of Bcl-2 contributes to cancer pathogenesis and resistance to chemotherapeutic drugs due to failed induction of apoptosis. Apoptosis serves to eliminate majority of the developing thymocytes that are either not recognized by major histocompatibility complexes or self-reactive. By gene targeting, we have demonstrated that retinoid-related orphan receptor gamma (RORgamma), a member of the nuclear receptor family, plays a critical role in the development of thymocytes and lymph nodes. In the absence of RORgamma, thymocytes undergo rapid apoptosis and unregulated entry into S phase of the cell cycle. Correspondingly, RORgamma deficient thymocytes have significant lower levels of anti-apoptotic Bcl-xL and cell cycle inhibitor p27kip1. Overexpression of Bcl-xL in the RORgamma deficient thymocytes restores survival and cell cycle progression. RORgamma null mice fail to develop lymph nodes, likely due to absence of lymph node progenitors in the early embryonic stages. We hypothesize that RORgamma regulates expression of the critical survival and cell cycle molecules that are required for the development of thymocytes and lymph nodes. We propose to study the molecular mechanisms responsible for RORgamma mediated transcription and its function in thymocyte maturation in vivo. In addition, we will examine how RORgamma regulates the development of peripheral lymphoid organs. The proposed studies will gain insight into nuclear receptor regulated functions in development of T cells and the secondary lymphoid tissues in vivo.