Dynamic Chromatin Alteration Induces Oncogenic Hijacking by Essential Transcriptional Factors during Medulloblastoma Tumorigenesis [ATAC-Seq]. Dynamic Chromatin Alteration Induces Oncogenic Hijacking by Essential Transcriptional Factors during Medulloblastoma Tumorigenesis [ATAC-Seq]

Using ATAC-seq analysis from GNPs to MBSHH we discovered a massive modification in chromatin accessibility during MBSHH formation. Next, using integrative bioinformatics, we identified genes of the nuclear factor I (NFI) family that function as oncogenes on the MBSHH epigenome. We demonstrate not only that these genes are essential in the early stages of murine MBSHHs tumorigenesis, but also that their genetic silencing inhibits tumor growth in murine and human MBSHHs in vitro and in vivo. Finally, we discovered that NFIA/B are post-translationally modified by an activating methylation in MBSHH, making it possibility to target this pathway. Further studies revealed that pharmacological inhibition of this methylated NFIA/B hindered tumor proliferation, demonstrating the requirement of NFIA/B for tumor progression. Collectively our data shed light on the mechanism underlying the epigenome during the formation of the most malignant pediatric brain tumor and emphasizes the importance of deciphering cancer-specific epigenome for identification of new therapeutic avenues. Overall design: Chromatin accessiblity of tumorigenesis process of medulloblastomas using mouse GEMM model; knockdown experiment of a medulloblastoma mouse cell line with siRNA (control siRNA and siNfia and siNfib)

我们通过对从颗粒神经元前体细胞（Granule neuron precursors, GNPs）至SHH亚型髓母细胞瘤（Medulloblastoma subgroup SHH, MBSHH）的样本开展转座酶可及性测序（ATAC-seq）分析，发现MBSHH形成过程中染色质可及性发生了大规模重塑。随后，我们借助整合生物信息学手段，鉴定出核因子I（nuclear factor I, NFI）家族基因可作为MBSHH表观基因组的致癌基因。本研究证实，此类基因在小鼠MBSHH肿瘤发生的早期阶段发挥不可或缺的作用；进一步实验表明，对其进行基因沉默可在体外及体内环境中抑制小鼠及人源MBSHH的肿瘤生长。最后，我们发现NFIA/B在MBSHH中通过激活型甲基化发生翻译后修饰，为该通路的靶向干预提供了可行性。后续研究显示，对该甲基化修饰后的NFIA/B实施药物抑制可阻碍肿瘤增殖，印证了NFIA/B对于肿瘤进展的必要性。综上，本研究的数据阐明了恶性程度最高的儿童脑肿瘤形成过程中表观基因组的潜在调控机制，并强调了解析癌症特异性表观组对于发掘全新治疗策略的重要价值。总体实验设计：采用基因工程小鼠模型（Genetically engineered mouse model, GEMM）探究髓母细胞瘤肿瘤发生过程中的染色质可及性；利用小干扰RNA（small interfering RNA, siRNA）对髓母细胞瘤小鼠细胞系开展基因敲低实验，设置阴性对照siRNA、siNfia及siNfib三组处理。