CRTC2 in Cellular Development, Function, and Neoplasia

描述(申请人提供)：大多数淋巴系统恶性肿瘤由生发中心(GC)经历的B细胞转化而来。在之前的两个资助时期，我们发现TCL1原癌基因在三种主要的GC B细胞淋巴瘤中异常表达，包括滤泡性(FL)、Burkitt(BL)和弥漫性大B细胞(DLBCL)淋巴瘤。两组特定的目标涉及Tcl1异常表达在GC B细胞转化中的致病作用以及在人类B细胞恶性肿瘤中调节和失调Tcl1表达的机制(S)。资金支持我们小组发表了66份同行评议的出版物。现在，我们建议从逻辑上将先前成功的工作范围从TCL1扩展到一个令人兴奋的新方向。在免疫反应中，B细胞在GC内经历免疫球蛋白(IG)基因的快速增殖和重塑，从而产生记忆B细胞和浆细胞。不幸的是，与这种“GC反应”相关的DNA损伤也促进了大多数B细胞恶性肿瘤的发生。我们最近发现，在GC B细胞的IG类开关重组(CSR)过程中，由AID依赖的DNA双链断裂(DSB)激活的ATM通过LKB1发出信号，灭活CREB的转录辅助激活因子CRTC2。利用全基因组定位分析，我们确定CRTC2失活出人意料地抑制了控制GC B细胞增殖、自我更新和分化为抗体(Ab)分泌浆细胞的遗传程序，同时反对淋巴肿大(见附录-Sherman等人，分子细胞，出版社，2010年)。在人类B细胞淋巴瘤的初步研究中，通过ATM或LKB1抑制，或者通过最近发现的CRTC2的体细胞突变或遗传多态，发现了这一途径的缺陷。关于CRTC2作为葡萄糖代谢的调节剂，我们已经知道了很多，我们现在已经证明DSB激活了GC B细胞中一条使CRTC2失活的途径。然而，到目前为止，CRTC2在细胞分化或癌症中的作用还没有被描述。在新的初步研究中，我们在GC B细胞中发现了一组来自CHIP-CHIP的CRTC2结合基因，随着CRTC2失活，CRTC2的表达增加而不是减少，这表明CRTC2在其CREB共激活功能之外还具有转录抑制活性。作为细胞分化和癌症的候选调节因子，我们提出了三个新的特异性目标来研究CRTC2在控制B细胞命运和功能中的作用。在目标1中，我们将确定CRTC2是否参与转录抑制。在目标2中，我们将结构性地激活GC B细胞中的CRTC2，并在体内评价其对B细胞分化和体液免疫的影响。在目标3中，我们将确定新的激活CRTC2改变是体细胞突变还是生殖系多态，并将研究CRTC2失活以避免淋巴肿大的必要性。总体而言，我们的研究将CRTC2的作用扩展到新陈代谢之外，并表征了一种意想不到的B细胞发育和功能的新调节因子。

DESCRIPTION (provided by applicant): Most lymphoid malignancies arise by transformation of germinal center (GC) experienced B cells. In two prior funding periods we showed that the TCL1 proto-oncogene was abnormally expressed in samples from three major GC B cell lymphoma categories, including follicular (FL), Burkitt (BL), and diffuse large B cell (DLBCL) lymphomas. Two sets of Specific Aims addressed a causative role for aberrant TCL1 expression in the transformation of GC B cells and the mechanism(s) for regulating and dysregulating TCL1 expression in human B cell malignancies. Funding supported our group for 66 peer-reviewed publications. Now, we propose to logically expand the scope of prior successful work beyond TCL1 into an exciting new direction. During an immune response, B cells undergo rapid proliferation and remodeling of immunoglobulin (IG) genes within GCs to generate memory B and plasma cells. Unfortunately, DNA damage associated with this "GC reaction" also promotes most B cell malignancies. We recently discovered that ATM, activated by AID- dependent DNA double-stranded breaks (DSBs) during IG class switch recombination (CSR) in GC B cells, signals through LKB1 to inactivate CRTC2, a known transcriptional co-activator of CREB. Using genome-wide location analysis, we determined that CRTC2 inactivation unexpectedly repressed a genetic program that controls GC B cell proliferation, self-renewal, and differentiation into antibody (Ab)-secreting plasma cells while opposing lymphomagenesis (see Appendix- Sherman, et al., Molecular Cell, in press, 2010). Defects in this pathway were identified in pilot studies of human B cell lymphomas by ATM or LKB1 repression, or by a recently identified somatic mutation or genetic polymorphism in CRTC2. Much is known about CRTC2 as a regulator of glucose metabolism, and we have now shown that DSBs activate a pathway in GC B cells that inactivates CRTC2. However, no role for CRTC2 in cell differentiation or cancer has been described to date. In new preliminary studies, we discovered a set of CRTC2 bound genes from ChIP-chip in GC B cells that increase rather than decrease in expression with CRTC2 inactivation, suggesting that CRTC2 also has transcriptional repression activity beyond its CREB co-activator function. As a candidate regulator of cell differentiation and cancer, we propose Three New Specific Aims to investigate the role of CRTC2 in controlling B cell fate and function. In Aim 1, we will determine whether CRTC2 participates in transcriptional repression. In Aim 2, we will constitutively activate CRTC2 in GC B cells and evaluate effects on B cell differentiation and humoral immunity in vivo. In aim 3, we will determine whether a new activating CRTC2 alteration is a somatic mutation or germline polymorphism and we will investigate the necessity for CRTC2 inactivation to avoid lymphomagenesis. Overall, our studies expand the role for CRTC2 beyond metabolism and characterize an unexpected new regulator of B cell development and function.