Single-cell epigenetic analysis reveals principles of chromatin states in H3.3-K27M gliomas

Cancer cells are highly heterogeneous at the transcriptional level and in their epigenetic state. Methods to study epigenetic heterogeneity are limited in throughput and information obtained per cell. Here, we adapted Cytometry by Time of Flight (CyTOF) to analyze a wide panel of histone modifications in primary tumor-derived lines of Diffused Intrinsic Pontine Glioma (DIPG). DIPG is a lethal glioma, driven by histone H3 lysine 27 mutation (H3-K27M). We identified two epigenetically distinct subpopulations in DIGP, reflecting inherent heterogeneity in expression of the mutant histone. These two subpopulations are robust across tumor lines derived from different patients and show differential proliferation capacity and expression of stem-cell and differentiation markers. Moreover, we demonstrate the use of this high-dimensional data to elucidate potential interactions between histone modifications and epigenetic alterations during the cell-cycle. Our work establishes new concepts for the analysis of epigenetic heterogeneity in cancer that could be applied to diverse biological systems.