To analyze the expression of the integral components of the SMN complex in the spinal cord of severe SMA mice, we isolated spinal cords from normal (SMN2+/+;mSmn+/+), carrier (SMN2+/+;mSmn+/−) and severe SMA (SMN2+/+;mSmn−/−) mice at postnatal day 3. Here, SMN1 is linked to proximal spinal muscular atrophy.