Axonal-SMN (a-SMN), a protein isoform of the survival motor neuron gene, is specifically involved in axonogenesis.
Spinal muscular atrophy (SMA) is an autosomal recessive disease of childhood due to loss of the telomeric survival motor neuron gene, SMN1. The general functions of the main SMN1 protein product, full-length SMN (FL-SMN), do not explain the selective motoneuronal loss of SMA. We identified axonal-SMN (a-SMN), an alternatively spliced SMN form, preferentially encoded by the SMN1 gene in humans. The a-SMN transcript and protein are down-regulated during early development in different tissues. In the spinal cord, the a-SMN protein is selectively expressed in motor neurons and mainly localized in axons. Forced expression of a-SMN stimulates motor neuron axonogenesis in a time-dependent fashion and induces axonal-like growth in non-neuronal cells. Exons 2b and 3 are essential for the axonogenic effects. This discovery indicates an unexpected complexity of the SMN gene system and may help in understanding the pathogenesis of SMA.
Setola
Veronica
V
Molecular Neuroanatomy Laboratory, Department of Experimental Neurophysiology and Epileptology, Istituto Neurologico C. Besta, Milano, Italy.
Terao
Mineko
M
Locatelli
Denise
D
Bassanini
Stefania
S
Garattini
Enrico
E
Battaglia
Giorgio
G
D000595:Amino Acid Sequence; D000818:Animals; D001369:Axons / Q000502:physiology*; D002454:Cell Differentiation / Q000235:genetics*; D002470:Cell Survival / Q000235:genetics; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000502:physiology; D009474:Neurons / Q000166:cytology*; D020033:Protein Isoforms / Q000235:genetics / Q000502:physiology; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D051381:Rats; D055532:SMN Complex Proteins; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism; D055533:Survival of Motor Neuron 1 Protein
D017362:Cyclic AMP Response Element-Binding Protein; D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; D016601:RNA-Binding Proteins; D055532:SMN Complex Proteins; C526471:SMN1 protein, human; C526473:Smn1 protein, rat; D055533:Survival of Motor Neuron 1 Protein