Research Projects

Spinal cord injury (SCI) leads to a catastrophic loss of neuronal communication, due to failed axonal regeneration, glial scar formation and disrupted axon guidance mechanism. A major barrier to functional recovery in the CNS is the inability of injured axons to regenerate and re-establish functional connections. Unlike the PNS, where axons exhibit strong regenerative potential, adult CNS axons form dystrophic retraction bulbs instead of growth cones. These retraction bulbs are characterized by disorganized, depolymerized microtubules, and lack actin and tubulin polymer domains critical for elongation. Even with therapeutic interventions, new neurons often fail to integrate due to the absence of molecular cues and structural guidance necessary for synaptic connectivity. The growth cone, a motile structure at the axon tip, relies on rapid cytoskeletal rearrangement and localized membrane delivery to navigate complex molecular terrains. Post-SCI environment is further complicated by the persistent release of potent inhibitors of axonal growth, secreted predominantly by glial cells. Extracellular vesicles (EVs) are lipid bilayer-encased nanoparticles secreted by nearly all cell types. These vesicles mediate intercellular communication by transporting diverse bioactive cargo, including proteins, lipids, mRNAs, and miRNAs, to recipient cells. Rab GTPases are known regulators of vesicular transport, functioning as controllable molecular “switches” that govern all stages of intracellular vesicle trafficking. Our recent work identified Rab27a, a small GTPase involved in vesicle trafficking and EV secretion, as a key mediator of Chondroitin Sulfate Proteoglycans (CSPG)-containing EV release after SCI. This process engages the Rho/ROCK signaling pathway, and alters pAkt and β-tubulin III levels, establishing Rab27a as a regulator of extracellular environment after SCI. We now propose that Rab27a also plays a critical intrinsic role in neurons by regulating EV trafficking involved in axon guidance, membrane remodeling, and growth cone dynamics. We hypothesize that Rab27a acts as a vesicular “switchboard” directing EVs containing guidance cues, membrane components, and signaling molecules to growth cone. These secreted EVs may undergo microtubule-dependent transport, essential for real-time growth cone steering and axon targeting post-injury. Despite Rab27a’s established roles in organelle transport, its role in neuronal circuit remodeling post-SCI remains unexplored. This proposal aims to test the hypothesis that Rab27a-mediated EV dynamics orchestrate axonal guidance and connectivity after SCI by: o Determining how Rab27a-positive EVs regulate neuronal microtubule dynamics and stability in neurons o Targeted identification and validation of guidance and cytoskeletal regulators in Rab27a-positive EVs o Investigating the spatial-temporal localization of Rab27a in injured neurons and growth cone o In vivo validation of Rab27a-mediated EV signaling and its role in axon guidance, glial response and functional recovery post-SCI We hypothesize that Rab27a not only governs the release of inhibitory EVs from astrocytes but also intrinsically regulates vesicle trafficking and guidance within neurons. By uncovering how Rab27a shapes the local environment and intracellular signaling at the growth cone, this study could redefine therapeutic strategies for SCI, either through targeted modulation of EV pathways or by harnessing Rab27a as a dual-acting therapeutic target. To ensure translational relevance, we propose a therapeutic roadmap based on our findings. This includes strategies such as AAV-mediated Rab27a modulation and EVs for targeted axonal regeneration. These approaches will allow us to validate Rab27a as a druggable target and assess its potential for clinical application in SCI.