Hao, L.T., Wolman, M., Granato, M., and Beattie, C.E. (2012) Survival motor neuron affects plastin 3 protein levels leading to motor defects. The Journal of neuroscience : the official journal of the Society for Neuroscience. 32(15):5074-5084.
The actin-binding protein plastin 3 (PLS3) has been identified as a modifier of the human motoneuron disease spinal muscular
atrophy (SMA). SMA is caused by decreased levels of the survival motor neuron protein (SMN) and in its most severe form causes
death in infants and young children. To understand the mechanism of PLS3 in SMA, we have analyzed pls3 RNA and protein in zebrafish smn mutants. We show that Pls3 protein levels are severely decreased in smn-/- mutants without a reduction in pls3 mRNA levels. Moreover, we show that both pls3 mRNA and protein stability are unaffected when Smn is reduced. This indicates that SMN affects PLS3 protein production. We
had previously shown that, in smn mutants, the presynaptic protein SV2 is decreased at neuromuscular junctions. Transgenically driving human PLS3 in motoneurons
rescues the decrease in SV2 expression. To determine whether PLS3 could also rescue function, we performed behavioral analysis
on smn mutants and found that they had a significant decrease in spontaneous swimming and turning. Driving PLS3 transgenically in
motoneurons rescued both of these defects. These data show that PLS3 protein levels are dependent on SMN and that PLS3 is
able to rescue the neuromuscular defects and corresponding movement phenotypes caused by low levels of Smn suggesting that
decreased PLS3 contributes to SMA motor phenotypes.