A Single-Cell Signaling Atlas of Spinal Cord BDNF Responses Reveals Determinants Beyond Receptor Expression

Although the influence of Brain-Derived Neurotrophic Factor (BDNF) has been characterized across numerous neural settings, how individual cells decode this pleiotropic message into context-dependent signaling responses remains unresolved. Using highly multiplexed single-cell mass cytometry to simultaneously measure levels of 19 signaling markers and 18 cell ID markers, we constructed a temporal atlas of BDNF-induced signaling relative to two control conditions across diverse spinal cord lineages and maturation states. We demonstrate that not all cells contribute to the global BDNF response with [~]47-75% of cells having increased ERK phosphorylation at peak activation. Our analysis of 20 uniquely identified cell identities reveals that TrkB/p75NTR receptor stoichiometry sets the potential for response, but ultimately the sustained reduction of surface TrkB predicts BDNF sensitivity. Surprisingly, identical receptor profiles in distinct cell types yield fundamentally different signaling responses, indicating that cell identity acts as the final arbiter of the BDNF message. These findings reframe BDNF sensitivity as a form of prepared competence. This work thus provides a framework for understanding how intracellular context dictates the functional interpretation of neurotrophic cues.