Mathematical Biology Seminar Nicholas Vierra, University of Utah, Tuesday, April 8, 2025 2:00pm in LCB 215 ER-plasma membrane junctions as signal processors for neuronal gene expression Abstract: Brain neurons convert electrical activity into biochemical signals that regulate gene expression, a process known as excitation-transcription (ET) coupling. Rather than a linear cascade, ET coupling functions as a computation, determining whether a stimulus is sufficient to trigger transcription. Despite its importance for learning and memory, the molecular mechanisms of ET coupling remain unclear. Evidence suggests that neuronal endoplasmic reticulum (ER) -plasma membrane (PM) junctions act as biochemical hubs for ET coupling. These junctions expand when neurons are silent and dissolve under strong excitation, dynamically concentrating second messengers and kinases that signal to the nucleus. This structural plasticity implies that ER-PM junctions integrate input strength, duration, and stimulus history to set the ET coupling threshold. In this talk, I will present experimental findings supporting this model and explore open questions about how these junctions function as timers, clocks, or signal integrators.