Nrg1 regulates cortical wiring and motor recovery upon traumatic injury.

Introduction: Traumatic brain injury (TBI) is a leading cause of disability, yet molecular mechanisms supporting cortical repair remain poorly defined. While Neuregulin 1 (Nrg1) is essential for cortical development, its role in traumatic cortical injury in adults is unclear. Methods: To circumvent developmental confounds, we used an inducible conditional Nrg1 knockout in the adult mouse and subjected it to controlled cortical damage (CCD) in the motor cortex. We combined high-resolution adeno-associated viral tracing of callosal projections with comprehensive behavioral, histological, and molecular analyses. Results: Nrg1 deletion led to significant impairments in structural connectivity and motor recovery, which were markedly exacerbated in mature mice, indicating a critical role for Nrg1 in adult cortical repair. Mechanistically, our data indicate that Nrg1 promotes this plasticity through intracellular domain (ICD) signaling, acting cell-autonomously to enhance axonal outgrowth in neuronal cultures. Furthermore, loss of Nrg1 was associated with altered perineuronal net (PNN) structure and increased neuroinflammation at the lesion site. Discussion: These findings identify endogenous Nrg1 as a key regulator of structural preservation and functional recovery after cortical injury, highlighting Nrg1 signaling as a potential target to enhance cortical plasticity following trauma.