Spinal muscular atrophy (SMA) is an autosomal recessive motor neuron disease with a high incidence and is the most common genetic cause of infant mortality. SMA is primarily characterized by degeneration of the spinal motor neurons that leads to skeletal muscle atrophy followed by symmetric limb paralysis, respiratory failure, and death. In humans, mutation of the Survival Motor Neuron 1 (SMN1)...

Our understanding of motor neuron differentiation is rapidly evolving. New studies demonstrate that cells in the periphery of the embryo provide feedback signals for spinal cord motor neurons that are instrumental in the timing and regulation of their development. Two papers in this issue of Neuron identify a motor neuron survival factor, GDNF, and the ETS transcription factor, PEA3, as key com...

Spinal muscular atrophy (SMA) is a frequent recessive autosomal disorder. It is caused by mutations or deletion of the telomeric copy of the survival motor neuron (SMN) gene, leading to depletion in SMN protein levels. The treatment rationale for SMA is to halt or delay the degeneration of motor neurons, but to date there are no effective drug treatments for this disease. We have previously dem...

Werdnig-Hoffmann disease (WHD) is the most severe clinical type of spinal muscular atrophy characterized by loss of lower motor neurons and paralysis. We examined the hypothesis that disease pathogenesis is based on an inappropriate persistence of normally occurring motor neuron programmed cell death. The diagnosis of WHD was made on the basis of clinical findings, electromyoneurography, and bi...

Mutations in the SMN1 (survival motor neuron 1) gene cause spinal muscular atrophy (SMA). We now show that SMN protein, the SMN1 gene product, interacts directly with the tumor suppressor protein, p53. Pathogenic missense mutations in SMN reduce both self-association and p53 binding by SMN, and the extent of the reductions correlate with disease severity. The inactive, truncated form of SMN pro...