The ability of axons to regenerate after injury is critical to restore the connectivity and functionality of damaged neurons. However, axon regeneration in the central nervous system (CNS) is actively inhibited by both intrinsic and extrinsic factors. As a result, CNS injury results in a currently untreatable and permanent loss of function. Developing a complete molecular understanding of how axon regeneration is inhibited is critical to repairing the injured nervous system. From my thesis research, I identified the highly conserved presynaptic protein CLA- 1/Clarinet, the sole C. elegans homolog of mammalian Piccolo and Bassoon, as a novel inhibitor of axon regeneration. Loss of CLA-1 robustly promotes axon regeneration in C. elegans with only minimal disruption of synaptic function in regenerated axons. This provides a unique opportunity to investigate how the canonical function of presynaptic proteins at the neuromuscular junction can be separated from their newly discovered role in axon regeneration. I found that the three splice isoforms of CLA-1 differentially regulate synapse development versus axon regeneration, with the medium isoform CLA-1M being necessary and sufficient to inhibit axon regeneration cell-autonomously. Mechanistically, CLA-1 inhibits regeneration independently of its active zone partner UNC-13/MUNC13, revealing the surprising finding that active zone proteins have evolved multiple strategies to inhibit axon regeneration. CLA-1 inhibits regeneration by downregulating the function of microtubule minus-end binding protein PTRN-1/CAMSAP. In cla-1 mutants, cargo trafficking along microtubules is protected against injury-induced microtubule disruptions to facilitate axon regrowth. Together, my findings add significantly to our current understanding of the role of synaptic proteins in the injury response and reveal a new strategy for promoting both axon regeneration and functional repair.