H3.3K27M cooperates with p53 loss and Pdgfra gain in mouse embryonic neural progenitor cells to induce invasive high-grade gliomas [Human RNA-Seq]

Gain-of-function mutations in histone 3 (H3) variants are found in a large proportion of pediatric high-grade gliomas (pHGG) and are often associated with p53 loss and PDGFRA amplification. However, a lack of faithful models has hampered investigation of disease mechanisms and preclinical development. Here, we describe a somatic mouse model of H3.3K27M-driven HGG, which faithfully recapitulates human H3.3K27M pHGG. H3.3K27M and p53 loss are sufficient for neoplastic transformation but only within a specific window of brain development. In this model, H3.3K27M primes the PDGFRA pathway during transformation, and accordingly gain of wild-type PDGFRA decreases latency and increases invasion. Finally, we reveal a previously underappreciated dynamic regulation of H3K27 trimethylation at specific loci. Overall, this experimental model provides key insights into oncohistone-driven pHGG pathogenesis and will enable investigations of future therapies. Overall design: We performed genome-wide transcriptome profiling (RNAseq) of 12 samples derived from human patients: matched normal brain controls (normal brain tissue from pediatric brain tumor patients; n = 3), pediatric high-grade gliomas (pHGG) that are wild-type for H3.3 and TP53 (n = 4), pHGG with H3.3K27M and loss-of-function TP53 mutations (n = 5).

组蛋白3（histone 3, H3）变体的功能获得性突变在大部分儿童高级别胶质瘤（pediatric high-grade gliomas, pHGG）中检出率颇高，且常伴随p53缺失与血小板衍生生长因子受体α（PDGFRA）扩增。然而，缺乏可靠的疾病模型一直阻碍了该疾病的机制研究与临床前药物开发。本研究构建了一种由H3.3K27M驱动的胶质瘤体细胞小鼠模型，该模型可精准重现人类H3.3K27M型儿童高级别胶质瘤的病理特征。仅需H3.3K27M突变与p53缺失即可引发肿瘤转化，但该过程仅局限于大脑发育的特定窗口期。在该模型中，H3.3K27M可在肿瘤转化阶段激活PDGFRA通路，因此野生型PDGFRA的过表达可缩短肿瘤潜伏期并增强侵袭能力。最后，我们揭示了特定基因组位点上H3K27三甲基化修饰此前未被充分重视的动态调控机制。综上，该实验模型为致癌组蛋白驱动的儿童高级别胶质瘤发病机制研究提供了关键见解，也将为未来的治疗探索提供重要支撑。整体实验设计：我们对12例人类来源样本开展了全基因组转录组测序（RNAseq），样本具体分为三类：匹配的正常脑组织对照（儿童脑肿瘤患者的正常脑组织，n=3）、H3.3与TP53均为野生型的儿童高级别胶质瘤（n=4）、携带H3.3K27M突变且TP53功能缺失的儿童高级别胶质瘤（n=5）。