Figure 4A shows Western blot analysis of SMN complex expression in whole spinal cord extracts from normal (SMN2+/+;mSmn+/+), carrier (SMN2+/+;mSmn+/−), severe SMA (SMN2+/+;mSmn−/−), SMNΔ7 SMA (SMN2+/+;SMNΔ7+/+; mSmn−/−), SMN(A2G) SMA (SMN2+/+;SMN(A2G)+/−; mSmn−/−) and high copy SMN2 SMA (SMN2+/−; SMN2(566)+/−;mSmn−/−) mice at postnatal day 3. The levels of Gemin2, Gemin6 and Gemin8 are strongly decreased in both severe SMA and SMNΔ7 SMA mice compared with normal and carrier mice (Figure 4A). This evidence concerns the gene SMN1 and proximal spinal muscular atrophy.