Repulsive Guidance Molecule A (RGMa), a membrane-associated protein expressed in the central nervous system. RGMa is a potent inhibitor of axonal growth and neuronal regeneration. In the context of acute neurological injuries like spinal cord injury or stroke, and in chronic conditions such as multiple sclerosis, RGMa is upregulated and acts as a "brake" on recovery. It inhibits neurite outgrowth, prevents the rewiring of neural circuits, and contributes to neuronal apoptosis.