MMP-9 controls onset of paralysis in ALS mice. Sections of muscle stained for nerve (green) and muscle (red); nerve-muscle contacts appear yellow. In the SOD1 mouse, muscles that move the eye (left) retain nerve contacts and are active. Fast leg muscles (center) in the same animal lose nerve contacts (red stain only) and become paralyzed. Fast muscles from which MMP-9 has been genetically removed (right) retain their nerve contacts, and therefore muscle function, for nearly 3 months longer. This suggests that inhibiting MMP-9 in human patients with ALS should be beneficial.