P2RX7 and major depressive disorder: Examining additional genes known to be implicated in depression and involved in either the glutamate/glutamine cycle (e.g., GLS1), regulation of neuronal plasticity and cellular resilience (e.g., BCL2), or purinergic signaling (e.g., P2RX7) may provide a better understanding of the underlying neurobiology of these glutamate-level alterations66–68.