Research
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OVERALL GOAL & MOTIVATION Our long-standing goal is to elucidate evolutionarily conserved mechanisms of spinal cord regeneration, and to develop zebrafish-inspired interventions to promote neural repair in mammals. Adult zebrafish possess an elevated regenerative capacity and lack the anti-regenerative complications displayed after mammalian nervous system injuries. Our laboratory aims to leverage the strengths of the zebrafish model system to uncover pro-regenerative cell identities and mechanisms in highly regenerative vertebrates, and to reconstruct analogous mechanisms in poorly regenerative mammals. |
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SPECIFIC PROJECTS
I- REPROGRAMMING ASTROCYTES TO PROMOTE NEURAL REPAIR
I- REPROGRAMMING ASTROCYTES TO PROMOTE NEURAL REPAIR
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As recent years brought major advances in neuron-intrinsic regenerative approaches, providing a permissive glial environment for regenerating neurons is an upcoming challenge and an underexplored avenue in regenerative medicine. Our studies showed zebrafish astroglia are pro-regenerative after injury. We are using comparative transcriptomics to comprehensively define pro-regenerative glial cell identities and states in zebrafish, and to identify molecular pathways that distinguish pro-regenerative cells in zebrafish from non-regenerative cells in mammals. Using the power of cell fate reprogramming, we are engineering human astrocytes that mimic the transcriptional and functional profiles of pro-regenerative astroglia in zebrafish. We posit that shifting human astrocytic cell states towards pro-regenerative phenotypes will minimize scarring and provide natural scaffolds for neural regeneration.
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II- INTERSECTING MODES OF NEURONAL REPAIR
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We recently reported a comprehensive single nuclear RNA sequencing atlas that identified cooperative roles for adult neurogenesis and neuronal plasticity during spinal cord repair. In addition to characterizing mechanisms of adult neurogenesis after injury, these studies identified a transient population of injury-responsive neurons (iNeurons) that show elevated plasticity 1 week post-injury. CRISPR/Cas9 mutagenesis showed iNeurons are required for functional recovery and employ vesicular trafficking as an essential mechanism that underlies neuronal plasticity. These studies provide a comprehensive resource of the cells and mechanisms that direct spinal cord regeneration and establish zebrafish as a model of plasticity-driven neural repair.
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III- POTENCY AND CONTRIBUTION OF PROGENITOR CELLS IN THE ADULT NERVOUS SYSTEM
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We hypothesize that localized niches of lineage-restricted progenitors contribute to either glial or neuronal regeneration after injury. We are pursuing a combination of cellular and molecular approaches to test this hypothesis. Cellularly, we are using genetic lineage tracing to dissect the contributions of progenitor cells during regeneration. Molecularly, we are using single-cell trancriptomics to determine progenitor cell identities in the zebrafish and mouse spinal cord. These studies provide a discovery platform to understand the molecular and cellular basis of regenerative capacity across species.
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IV- PRO-REGENERATIVE IMMUNE RESPONSES AND ELEVATED PHAGOCYTIC CAPACITY
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Immune cells elicit a continuum of transcriptional and functional states after spinal cord injury. In mammals, inefficient debris clearance and chronic inflammation impede recovery and overshadow pro-regenerative immune functions. Unlike mammals, zebrafish SCI elicits transient immune activation and efficient debris clearance, without causing chronic inflammation. Cross-species comparisons between zebrafish and mammalian microglia/macrophages identified macrophage-enriched zebrafish genes including tcim. These studies establish a central requirement for elevated phagocytic capacity to achieve innate spinal cord repair. We propose that further detailed diseection of immune cell states after zebrafish SCI will inspire manipulations to promote debris clearance and neural repair across species.
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V- DISCOVERY PROJECTS
We described an experimental pipeline that combines high-efficiency CRISPR/Cas9 mutagenesis with functional phenotypic screening to identify genes required for spinal cord repair in adult zebrafish (Jensen et al., Front Mol Neurosci, 2023; Burris et al., JoVE, 2021; Klatt Shaw and Mokalled, G3, 2021). These studies provide a platform that enabled us to perform medium- to large-scale genetic studies in adult zebrafish.
