Optogenetic Interrogation of Functional Synapse Formation by Corticospinal Tract Axons in the Injured Spinal Cord

Jayaprakash, Naveen; Wang, Zimei; Hoeynck, Brian; Krueger, Nicholas; Kramer, Audra A.; Balle, Eric; Wheeler, Daniel S.; Wheeler, Robert; Blackmore, Murray G.

doi:10.1523/jneurosci.4203-15.2016

Cited by 46 publications

(35 citation statements)

References 63 publications

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“…hM4Di activation transiently hyperpolarizes the neuron and suppresses presynaptic glutamate release (Roth, 2016), thus allowing the role of the dorsolateral corticospinal pathway in mediating spontaneous recovery following cervical spinal cord injury to be determined (Hilton et al, 2016a). In principle, such strategies will allow researchers to assess whether a manipulation promotes synaptic transmission or to probe the necessity of specific neuron populations in function after injury (Hilton et al, 2016a;Jayaprakash et al, 2016;Kadoya et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

Can injured adult CNS axons regenerate by recapitulating development?

2017

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In the adult mammalian central nervous system (CNS), neurons typically fail to regenerate their axons after injury. During development, by contrast, neurons extend axons effectively. A variety of intracellular mechanisms mediate this difference, including changes in gene expression, the ability to form a growth cone, differences in mitochondrial function/axonal transport and the efficacy of synaptic transmission. In turn, these intracellular processes are linked to extracellular differences between the developing and adult CNS. During development, the extracellular environment directs axon growth and circuit formation. In adulthood, by contrast, extracellular factors, such as myelin and the extracellular matrix, restrict axon growth. Here, we discuss whether the reactivation of developmental processes can elicit axon regeneration in the injured CNS.

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Section: Discussionmentioning

confidence: 99%

Can injured adult CNS axons regenerate by recapitulating development?

2017

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“…1 million cells were injected by Picospritzer 5 to five locations surrounding the injury site in thrombin / fibrinogen and BDNF, VEFF, bFGF and MDL28170VEGF (BDNF 50ng/µl, bFGF 10ng/µl, VEGF 10ng/µl, MDL28170 50µM) Behavior. As described previously (26) mice were pre-trained on a horizontal ladder (30cm long, 1cm rung spacing) and staircase pellet apparatus (Lafayette Instruments, Lafayette IN) until performance plateaued, then tested every four weeks (ladder) or bi-weekly (retrieval) after injury.…”

Section: Methodsmentioning

confidence: 99%

“…In this way optical stimulation specifically triggers synaptic release from CST terminals, which uniquely express ChR2 in spinal tissue. At each location, a 32-multichannel electrode was inserted 1000µm into the spinal cord, with sensitivity to activity from individual cell bodies but not fibers of passage (26). Spontaneously active units were identified and the average change in firing during light exposure was calculated for each unit.…”

Section: Regenerated Cst Axons Form Functional Synapses On Distal Spimentioning

confidence: 99%

Restoration of Direct Corticospinal Communication Across Sites of Spinal Injury

Jayaprakash

Nowak

Eastwood

et al. 2019

Preprint

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Injury to the spinal cord often disrupts long-distance axon tracts that link the brain and spinal cord, causing permanent disability. Axon regeneration is then prevented by a combination of inhibitory signals that emerge at the injury site and by a low capacity for regeneration within injured neurons. The corticospinal tract (CST) is essential for fine motor control but has proven refractory to many attempted pro-regenerative treatments. Although strategies are emerging to create relay or detour circuits that reroute cortical motor commands through spared circuits, these have only partially met the challenge of restoring motor control. Here, using a murine model of spinal injury, we elevated the intrinsic regenerative ability of CST neurons by supplying a pro-regenerative transcription factor, KLF6, while simultaneously supplying injured CST axons with a growth-permissive graft of neural progenitor cells (NPCs) transplanted into a site of spinal injury. The combined treatment produced robust CST regeneration directly through the grafts and into distal spinal cord. Moreover, selective optogenetic stimulation of regenerated CST axons and single-unit electrophysiology revealed extensive synaptic integration by CST axons with spinal neurons beyond the injury site. Finally, when KLF6 was delivered to injured neurons with a highly effective retrograde vector, combined KLF6/NPC treatment yielded significant improvements in forelimb function. These findings highlight the utility of retrograde gene therapy as a strategy to treat CNS injury and establish conditions that restore functional CST communication across a site of spinal injury. Significance StatementDamage to the spinal cord results in incurable paralysis because axons that carry descending motor commands are unable to regenerate. Here we deployed a two-pronged strategy in a rodent model of spinal injury to promote regeneration by the corticospinal tract, a critical mediator of fine motor control. Delivering pro-regenerative KLF6 to injured neurons while simultaneously transplanting neural progenitor cells to injury sites resulted in robust regeneration directly through sites of spinal injury, accompanied by extensive synapse formation with spinal neurons. In addition, when KLF6 was delivered with improved retrograde gene therapy vectors, the combined treatment significantly improved forelimb function in injured animals. This work represents important progress toward restoring regeneration and motor function after spinal injury.

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“…Inoue et al (53) did not test for antidromic action potentials and neither has any other optogenetic study in the monkey as of yet. In rodents, optogenetic stimulation of axon terminals evoked antidromic action potentials in some studies (56-59) but not others (33,(60)(61)(62)(63). Light intensity and the pathway under study appear to be key factors.…”

Section: Sensationmentioning

confidence: 95%

Primate optogenetics: Progress and prognosis

El-Shamayleh

Horwitz

2019

Proc. Natl. Acad. Sci. U.S.A.

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Monkeys are a premier model organism for neuroscience research. Activity in the central nervous systems of monkeys can be recorded and manipulated while they perform complex perceptual, motor, or cognitive tasks. Conventional techniques for manipulating neural activity in monkeys are too coarse to address many of the outstanding questions in primate neuroscience, but optogenetics holds the promise to overcome this hurdle. In this article, we review the progress that has been made in primate optogenetics over the past 5 years. We emphasize the use of gene regulatory sequences in viral vectors to target specific neuronal types, and we present data on vectors that we engineered to target parvalbumin-expressing neurons. We conclude with a discussion of the utility of optogenetics for treating sensorimotor hearing loss and Parkinson’s disease, areas of translational neuroscience in which monkeys provide unique leverage for basic science and medicine.

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Optogenetic Interrogation of Functional Synapse Formation by Corticospinal Tract Axons in the Injured Spinal Cord

Cited by 46 publications

References 63 publications

Can injured adult CNS axons regenerate by recapitulating development?

Can injured adult CNS axons regenerate by recapitulating development?

Restoration of Direct Corticospinal Communication Across Sites of Spinal Injury

Primate optogenetics: Progress and prognosis

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