C. elegans Spastin/spas-1 Is Required for Axon Regeneration and Maintenance.

Spastin is a conserved microtubule-severing enzyme mutated in hereditary spastic paraplegia. The role that spastin plays in the cell biology of axon regeneration and degeneration has recently been investigated in Drosophila We show that the C. elegans spastin ortholog, spas-1, is expressed in GABA motor neurons, in addition to the known expression in touch receptor neurons (TRNs) and that it is required for axon regeneration in the GABA motor neurons after in vivo laser axotomy. We identified no neuronal developmental defects in the GABA motor neurons and only minor branching variations in the TRNs. However, we show that spas-1 is required for the long-term maintenance of TRN axons in C. elegans, as older spas-1 null C. elegans show a significant increase in specific axonal morphological defects compared with the wild type as identified by confocal microscopy in aged animals. Together, our results suggest that spastin is required for regrowth and maintenance of axons in C. elegans, consistent with previous reports in Drosophila.