CNSC-44. EVOLUTION OF NEURON-GLIOMA CIRCUIT DYNAMICS THROUGH EPH-A MEDIATED AXONOGENESIS

Abstract Pediatric high-grade gliomas (pHGG) are aggressive primary brain neoplasms with a dismal prognosis, making them the leading cause of brain tumor-related deaths in children. pHGGs occur in specific anatomical locations at specific ages underscoring their origin in neurodevelopment and the critical importance of the brain tumor microenvironment. Many pHGGs originate from oligodendroglial precursor cells (OPCs) and, like OPCs, neuronal activity promotes the proliferation of pHGGs. Neuronal activity drives pHGG growth through electrochemical communication with pHGG cells. In turn, pHGGs increase neuronal excitability and remodel functional neural circuits. The interconnected network of glioma cells and neurons is fundamental to pHGG progression. Using single-nuclei RNA sequencing of mice harboring murine H3K27M-altered Diffused Midline Glioma (DMG), we observed gene expression changes indicating an increase in axonogenesis processes in glioma-associated neurons (GANs), primarily driven by EphA signaling. EphA4, EphA5, and EphA7 are overexpressed in GANs while the ligand, EphrinA1, is overexpressed in H3K27M gliomas. Performing in vitro neurite outgrowth and co-culture assays, we observed increased axonogenesis in neurons in the presence of DMG cells and DMG-conditioned media. We developed a two-color in vivo imaging method to study neuron-glioma interactions over time in freely behaving mice enabling us to record the frequency, pattern, and synchronicity of calcium transients in neurons, glioma cells, and their coactivity, giving us a comprehensive view of the changes in neuron-glioma circuit dynamics over time. We have observed increasing neuronal activity and synchronicity throughout the disease. We have also observed that gliomas also exhibit increased levels of activity and synchronicity as the tumor progresses. We verified our findings through longitudinal in vivo local field potential recordings, finding an increase in all power bands, especially in high-gamma activity over time. Ongoing experiments will test how glioma-induced axonogenesis contributes to the observed evolution of malignant circuit dynamics over time. Taken together, our data shows as gliomas progress, the neuron-glioma malignant circuitry evolves through axonogenesis driven by EphA signaling.