Spinal muscular atrophies (SMA) are frequent autosomal recessive disorders 
characterized by degeneration of lower motor neurons. SMA are caused by 
mutations of the survival of motor neuron gene (SMN1) leading to a reduction of 
the SMN protein amount. The identification of SMN interacting proteins involved 
in the formation of the spliceosome and splicing changes in SMN-deficient 
tissues of mutant mice strongly support the view that SMN is involved in the 
splicing reaction. However, the molecular pathway linking SMN defect to the SMA 
phenotype remains unclear. From a better knowledge of the genetic basis of SMA 
and the defects resulting from the mutations of SMN1 in cellular or animal 
models, several therapeutics strategies have been selected aiming at targeting 
SMN2, a partially functional copy of SMN1 gene which remains present in 
patients, or to prevent neurons from death. Refined characterization of the 
degenerative process in SMA and the identification of the defective molecular 
pathway downstream from the SMN defect will provide further exciting insight 
into this disease in the near future. They should contribute to clarify the 
pathophysiology of SMA, the function of SMN and should help in designing 
potential targeted or non-targeted therapeutic molecules.