Role of SMARCD3/BAF60C in neurodevelopment and medulloblastoma

项目摘要/摘要 髓母细胞瘤(MB)是一种发生于小脑的快速生长的异质性脑肿瘤。第三组，一组 在四个MB亚型(WNT、SHH、第3组和第4组)中，是儿童中最具侵袭性和恶性的类型。 第三组占所有MB的25%-30%，其特点是确诊时转移频繁，最严重 预后。虽然手术切除、放射治疗和化疗在消除某些形式上是有效的， 第三组患者不能用传统疗法治愈，也面临着缺乏分子靶向的 治疗。这项应用的总体目标是确定调节肿瘤的分子机制 组3中的转移性扩散。关键需要候选路径来提供合理的线索 为患有甲基溴的儿童提供新的有效治疗方法。初步研究表明SMARCD3/BAF60c (以下简称SMARCD3)是SWI/SNF染色质重塑复合体的核心成分，在 3MB组和发育期小脑浦肯野细胞(PC)。此外，SMARCD3的提升 表达与患者不良预后、MB转移表型和Reelin激活相关 小脑发育中PC迁移和定位所需的信号通路。中环 这一应用的假设是SMARCD3相关的SWI/SNF染色质重塑复合体 在小脑发育过程中调节PC迁移和定位的Reelin信号通路；然而，这 神经发育计划因MB转移扩散而被劫持。核心假说将得到检验 通过追求两个具体目标：1)调查SMARCD3在PC迁移和定位中的作用 小脑发育；以及2)确定SMARCD3-Reelin信号与转移的联系机制 MB的表型。在第一个目标下，将通过交叉Smarcd3 Flox/Flox产生一个新的老鼠模型 PC特异性基因启动子(L7/Pcp2)驱动的Cre小鼠。SMARCD3相关基因的作用 SWI/SNF染色质重塑复合体在小脑发育中的作用将用这只小鼠来研究 模特。对于第二个目标，体外和体内获得/丧失功能的方法在人MB细胞系和 异种移植小鼠模型将用于检测SMARCD3-Reelin信号介导的肿瘤转移 传播。此外，还将执行ATAC和芯片测序，以确定SMARCD3- 相关的SWI/SNF复合体调节Reelin信号通路。在本申请中提出的研究 是创新的，因为它专注于了解SMARCD3在神经发育和 髓母细胞瘤，以及肿瘤细胞劫持神经发育信号导致转移的前景。 这项拟议的研究意义重大，因为它有望提供令人信服的功能证据 SMARCD3及其相关的SWI/SNF复合体参与小脑发育、肿瘤转移、 以及早期大脑发育和肿瘤发生之间的分子联系。归根结底，这种知识 有可能为MB患者开发创新疗法提供新的理由。

Project Summary/Abstract Medulloblastoma (MB) is a fast-growing and heterogeneous brain tumor arising in the cerebellum. Group 3, one of four MB subgroups (WNT, SHH, Group 3, and Group 4), is the most aggressive and malignant type in children. Group 3, accounting for 25%-30% of all MB, is characterized by frequent metastasis at diagnosis and the worst prognosis. Although surgical resection, radiotherapy, and chemotherapy are effective at eliminating some forms, patients with Group 3 cannot be cured with conventional therapies and also face a paucity of molecularly targeted therapies. The overall objective in this application is to define the molecular mechanisms that regulate tumor metastatic dissemination in Group 3. Candidate pathways are critically needed to provide rational leads for enabling new and effective therapies for children with MB. Preliminary studies reveal that SMARCD3/BAF60C (SMARCD3 hereafter), a core component of SWI/SNF chromatin-remodeling complexes, is highly expressed in Group 3 MB and Purkinje cells (PCs) of the developing cerebellum. Furthermore, elevated SMARCD3 expression is associated with patient poor outcomes, MB metastatic phenotype, and activation of the Reelin signaling pathway that is required for PC migration and positioning in cerebellar development. The central hypothesis of this application is that the SMARCD3-associated SWI/SNF chromatin-remodeling complex regulates Reelin signaling pathway in PC migration and positioning during cerebellar development; however, this neurodevelopmental program is hijacked for MB metastatic dissemination. The central hypothesis will be tested by pursuing two specific aims: 1) investigate the role of SMARCD3 in PC migration and positioning during cerebellar development; and 2) define the mechanism linking SMARCD3-Reelin signaling to metastatic phenotype in MB. Under the first aim, a new mouse model will be generated by crossing the Smarcd3 flox/flox mouse with a PC-specific gene promoter (L7/Pcp2)-driven Cre mouse. The role of SMARCD3-associated SWI/SNF chromatin-remodeling complexes in cerebellar development will be investigated using this mouse model. For the second aim, in vitro and in vivo gain/loss-of-function approaches in human MB cell lines and xenograft mouse models will be used to test SMARCD3-Reelin signaling-mediated tumor metastatic dissemination. Additionally, ATAC- and ChIP-sequencing will be performed to determine how SMARCD3- associated SWI/SNF complexes regulate the Reelin signaling pathway. The research proposed in this application is innovative because it focuses on understanding the role of SMARCD3 in both neurodevelopment and medulloblastoma, and the prospect of tumor cells hijacking neurodevelopmental signaling resulting in metastasis. The proposed research is significant because it is expected to provide compelling functional evidence of SMARCD3 and the associated SWI/SNF complexes’ involvement in cerebellar development, tumor metastasis, and the molecular connections between early brain development and tumorigenesis. Ultimately, such knowledge has the potential of offering new rationales for the development of innovative therapies for patients with MB.