Simple SummaryPediatric high-grade gliomas bearing either an H3G34V/R or H3K27M mutation are incurable brain tumors with unique epigenomes. Current epigenomic studies on pHGGs primarily focus on these mutations; however, the function of other important crosstalk histone posttranslational modifications must be determined to elucidate tumor mechanisms. Here, we show that WDR82-mediated H3K4me3 is an important determinant of pediatric glioma malignancy and therapeutic response, and thus a potential epigenetic therapeutic target for children with malignant gliomas.AbstractPediatric high-grade gliomas (pHGGs) are common malignant brain tumors without effective treatment and poor patient survival. Abnormal posttranslational modification at the histone H3 tail plays critical roles in tumor cell malignancy. We have previously shown that the trimethylation of lysine 4 at histone H3 (H3K4me3) plays a significant role in pediatric ependymoma malignancy and is associated with tumor therapeutic sensitivity. Here, we show that H3K4me3 and its methyltransferase WDR82 are elevated in pHGGs. A reduction in H3K4me3 by downregulating WDR82 decreases H3K4me3 promoter occupancy and the expression of genes associated with stem cell features, cell proliferation, the cell cycle, and DNA damage repair. A reduction in WDR82-mediated H3K4me3 increases the response of pediatric glioma cells to chemotherapy. These findings suggest that WDR82-mediated H3K4me3 is an important determinant of pediatric glioma malignancy and therapeutic response. This highlights the need for a more thorough understanding of the potential of WDR82 as an epigenetic target to increase therapeutic efficacy and improve the prognosis for children with malignant gliomas.