CRTC2 in Cellular Development, Function, and Neoplasia

描述（由申请方提供）：大多数淋巴恶性肿瘤是由生殖中心（GC）经历的B细胞转化引起的。在之前的两个资助期内，我们发现TCL 1原癌基因在三种主要GC B细胞淋巴瘤类别的样本中异常表达，包括滤泡性（FL）、伯基特（BL）和弥漫性大B细胞（DLBCL）淋巴瘤。两组特定目的阐述了异常TCL 1表达在GC B细胞转化中的致病作用以及人B细胞恶性肿瘤中调节和失调TCL 1表达的机制。资金支持我们的66个同行评审的出版物。现在，我们建议从逻辑上扩展先前成功工作的范围，超越TCL 1，进入一个令人兴奋的新方向。在免疫应答期间，B细胞经历GC内免疫球蛋白（IG）基因的快速增殖和重塑，以产生记忆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。我们最近发现，ATM在GC B细胞中IG类别转换重组（CSR）期间被AID依赖性DNA双链断裂（DSB）激活，通过LKB 1向CREB B的已知转录共激活因子CRTC 2发出信号。使用全基因组定位分析，我们确定CRTC 2失活意外地抑制了控制GC B细胞增殖、自我更新和分化为分泌抗体（Ab）的浆细胞的遗传程序，同时对抗淋巴瘤发生（参见附录-谢尔曼等人，Molecular Cell，in press，2010）。在人B细胞淋巴瘤的初步研究中，通过ATM或LKB 1抑制，或通过最近鉴定的CRTC 2体细胞突变或遗传多态性，鉴定了该途径的缺陷。关于CRTC 2作为葡萄糖代谢的调节剂已经知道很多，我们现在已经表明DSB激活GC B细胞中使CRTC 2失活的途径。然而，迄今为止还没有描述CRTC 2在细胞分化或癌症中的作用。在新的初步研究中，我们在GC B细胞中发现了一组来自ChIP芯片的CRTC 2结合基因，其表达随着CRTC 2失活而增加而不是减少，这表明CRTC 2还具有超出其CREB共激活因子功能的转录抑制活性。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的来研究CRTC 2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CRTC 2是否参与转录抑制。在目的2中，我们将组成性激活GC B细胞中的CRTC 2，并评估对体内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CRTC 2改变是体细胞突变还是种系多态性，我们将研究CRTC 2失活以避免淋巴瘤发生的必要性。总体而言，我们的研究扩展了CRTC 2的作用，超越了代谢，并表征了B细胞发育和功能的一种意想不到的新调节剂。

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.