Chromatin Structure and Dynamics in Diffuse intrinsic pontine glioma (DIPG)

Change in chromatin structure and function underlie many different pathologies, which affect the brain. One disorder, which is caused by a direct point mutation in one of the genes encoding for histones is Diffuse Intrinsic Pontine Glioma (DIPG). DIPG is a specific type of cancer occurring in glial cells in the brain stem in children. Specific point mutations (K27M) in the histone variant H3.3 induce this type of glioma in a dominant negative fashion, potentially due to antagonizing Polycomb function. Other mutations in this histone variant are involved in other types of cancers. We developed a cellular model, based on mouse embryonic stem cells, where Doxycyclin (Dox) addition induces the expression of the mutant gene, H3.3K27M. Using RNA-seq and epigenomic profiling of different histone modifications, we report the initial molecular changes that occur once H3.3 is mutated. Moreover, using Time-seq (ChIP-seq for WT/Mut H3.3 at different time points), we were able to follow the dynamic turnover of WT and mutant H3.3. Our systems provide a first glimpse into the epigenetic changes that occur after the acquisition of the H3.3 mutation, allowing us to study the very first and dynamic effects of the mutated protein in healthy cells before the development and progression of cancer.