Sarm1 Deletion, but Not WldS, Confers Lifelong Rescue in a Mouse Model of Severe Axonopathy

Studies with the Wld(S) mutant mouse have shown that axon and synapse pathology in several models of neurodegenerative diseases are mechanistically related to injury-induced axon degeneration Wallerian degeneration). Crucially, an absence of SARM1 delays Wallerian degeneration as robustly as Wld(S), but their relative capacities to confer long-term protection against related, non-injury axonopathy and/or synaptopathy have not been directly compared. While Sarm1 deletion or Wld(S) can rescue perinatal lethality and widespread Wallerian-like axonopathy in young NMNAT2-deficient mice, we report that an absence of SARM1 enables these mice to survive into old age with no overt phenotype, whereas those rescued by Wld(S) invariantly develop a progressive neuromuscular defect in their hindlimbs from around 3 months of age. We therefore propose Sarm1 deletion as a more reliable tool than Wld S for investigating Wallerian-like mechanisms in disease models and suggest that SARM1 blockade may have greater therapeutic potential than WLDS-related strategies.