The G-protein Alpha Subunit Gs alpha Is A Tumor Suppressor In Sonic Hedgehog-driven Medulloblastoma [RNA-Seq]

Medulloblastoma, the most common malignant pediatric brain tumor, is highly heterogeneous with distinct molecular subtypes and cellular origins. Although current treatments improve survival rates, patients suffer severe treatment-related side effects and often relapse of tumors carrying resistance mutations, underscoring an urgent need for alternative targeted therapies. Currently, the genetic alterations underlying this disease are not fully understood. Here we identify GNAS, encoding the G-protein Gs-alpha, as a potent tumor suppressor gene in medulloblastoma. GNAS specifically defines a subset of aggressive Sonic Hedgehog (Shh)-group medulloblastomas. Gnas loss-of-function in distinct lineage progenitors of the developing hindbrain suffices to initiate medulloblastoma. We find that Gs-alpha is highly enriched at primary cilia of granule neuron precursors and suppresses Shh signaling not only by regulating classic cAMP-dependent pathway but also controlling ciliary trafficking of Smoothened. Concurrent cAMP elevation and Smoothened inhibition robustly arrests tumor cell growth in Gnas mutants. We further reveal oligodendrocyte progenitors as a novel cellular origin for anatomically-distinct Shh-associated medulloblastomas. Together, we identify a previously unrecognized tumor suppressor function of Gs-alpha in medulloblastoma partially mediated through inhibiting Shh signaling, and uncover Gs-alpha as a molecular link across disparate cells of origin among Shh-group medulloblastomas, pointing to G- protein modulation as a potential therapeutic avenue. Purpose: To known the gene expression profile of Medulloblastoma which drived by Gnas mutation Methods: mRNAs isolated from the cerebellum of control and Gnas mutants Results:Upregulation of Shh Signaling components in tumors Conclusions: The deletion of Gnas in hGFAP and Olig1 possitive cells result in substantial upregulation of shh signaling and formation of Medulloblastoma cerebellum mRNA profiles of 3 60-day old wild type (Ctrl) and 8 Olig1Cre driven Gsa conditional knockout or 8 hGFAPCre driven conditional knockout mice were generated by deep sequencing using Illumina Hiseq2000髓母细胞瘤（Medulloblastoma）是儿童最常见的恶性脑肿瘤，具有高度异质性，存在多种不同的分子亚型与细胞起源。尽管当前治疗手段可提升患者生存率，但患儿会遭受严重的治疗相关不良反应，且携带耐药突变的肿瘤常出现复发，这凸显了开发替代性靶向治疗方案的迫切需求。目前，人们对该疾病背后的遗传改变机制尚未完全阐明。 本研究鉴定出编码G蛋白Gs-α的GNAS基因是髓母细胞瘤中一种强效的抑癌基因。GNAS可特异性标识一组侵袭性的音猬因子（Sonic Hedgehog, Shh）组髓母细胞瘤亚群。在发育后脑的不同谱系祖细胞中，Gnas功能缺失足以诱发髓母细胞瘤。研究发现，Gs-α在颗粒神经元前体细胞的初级纤毛中高度富集，其不仅通过调控经典的环磷酸腺苷（cAMP）依赖通路抑制Shh信号通路，还可控制平滑蛋白（Smoothened）的纤毛转运过程。同时升高cAMP水平并抑制平滑蛋白，可强效阻滞Gnas突变体中肿瘤细胞的增殖。本研究进一步揭示少突胶质细胞祖细胞是解剖结构独特的Shh相关髓母细胞瘤的新型细胞起源。 综上，本研究证实了Gs-α在髓母细胞瘤中此前未被发现的抑癌功能，该功能部分通过抑制Shh信号通路实现；同时揭示Gs-α是Shh组髓母细胞瘤中不同细胞起源之间的分子关联因子，提示G蛋白调控可作为潜在的治疗方向。 研究目的：阐明Gnas突变驱动的髓母细胞瘤的基因表达谱特征。 实验方法：从对照组与Gnas突变小鼠的小脑组织中分离mRNA。 实验结果：肿瘤组织中Shh信号通路相关组分表达上调。 结论：在人胶质纤维酸性蛋白（hGFAP）与少突胶质细胞转录因子1（Olig1）阳性细胞中敲除Gnas，可显著上调Shh信号通路活性并诱发小脑髓母细胞瘤。 本研究通过Illumina Hiseq2000平台对3只60日龄野生型（对照组）小鼠、8只由Olig1Cre驱动的Gsa条件性敲除小鼠以及8只由hGFAPCre驱动的条件性敲除小鼠的小脑mRNA表达谱进行深度测序。