Christopher V. Gabel, Ph.D.
B.A. Princeton University
Ph.D. Harvard University
Research in our laboratory is focused around a common theme to understand how neuronal activity and cellular calcium signaling modulates neuronal response and regeneration following cellular damage. Employing the nematode worm C. elegans as a simple yet powerful model system, we pursue in vivo studies at both the single neuron and small circuit levels. Through our work and that of others, C. elegans has recently emerged as a powerful system for the study of neuronal damage and regeneration, following a long tradition of seminal findings in C. elegans with direct translation to mammalian systems. For our specific purposes its simple, completely mapped nervous system, small transparent body and amenable genetics make C. elegans an ideal test bed for novel biophotonic techniques and applications. The results are exciting, technologically driven breakthroughs that are pushing current understanding in regenerative neurobiology and small circuit function. As such, our laboratory is truly cross-disciplinary with engineers and biophysicists working side-by-side with traditional biologist. The technical expertise and ongoing research projects in the laboratory are as follows.
•Femtosecond Laser Surgery: Using an ultra-fast infrared-pulsed laser we can selectively ablate biological tissue with sub-micron resolution. This enables selective ablation of sub-cellular structures with minimal collateral damage. Applied to C. elegans this allows us to reproducibly identify, target and selectively sever a specific neuron at a particular location in vivo (Fig. 1 A,B)
•Microfluidics and Time-Lapse Imaging: We employ microfluidic devices (as well as additional techniques) to manipulate and immobilize unanesthetized C. elegans for in vivo laser surgery and extended time-lapse imaging of subsequent neuronal regeneration (Fig. 1 C)
•Fluorescent Calcium Imaging: Employing genetically encoded fluorescent calcium indicators, we can optically measure neuronal activity and cellular physiology in vivo. Combined with laser surgery this allows study of cellular calcium signaling and neuronal activity in response to specific cellular damage.
•Quantitative Behavioral Measurements: Computer automated tracking of C. elegans allows quantitative measurement of animal behavior and its alteration by acute laser dissection of specific neurons.
Calcium imaging in regeneration
Following neuronal damage, dramatic “calcium overload” can lead to cell degeneration and death, while subtle calcium signaling is essential for outgrowth and guidance of a regenerating axon. Despite its obvious importance in mediating neuron fate following insult, little is known of the localized intracellular calcium dynamics that occur in vivo within an injured neuron, or of the molecular components that modulate them. Our biophotonic techniques allow unprecedented high resolution in vivo time-lapse imaging of intracellular calcium dynamics and regenerative outgrowth following laser severing of a specific neuron. The quantitative nature of our single neuron regeneration assays coupled with the power of C. elegans genetics facilitates rapid and comprehensive analysis of pertinent genetic mutations, generating new insight into the molecular mechanisms that govern neuronal calcium response to damage. As such, our uniquely powerful experimental system is addressing critical gaps in the field of regenerative medicine that to date, despite intense effort, is largely ineffective in the treatment of traumatic neuronal damage and neurodegenerative diseases. By defining molecular mechanisms that mediate cellular calcium signals and their targets, our work will ultimately point to novel neurotherapeutic strategies that improve neuronal survival and recovery.
Apoptotic caspase activation for a beneficial role in neuronal regeneration
In our recent study, we demonstrated that the CED-3 caspase, well known as the core apoptotic cell death executioner, acts in early responses to neuronal injury to promote rapid axon regeneration in C. elegans (Pinan-Lucarre et al. PLoS Biology, 2012). This was the first evidence of a constructive role for caspase activity in neuronal repair and follows other findings implementing similar mechanisms in a wide range of neuronal processes including neurite pruning and synaptic modulation in vertebrates. A critical element of such mechanisms is the precise localized control of caspase activity while not inducing generalized apoptotic cell death. Our study implicated a novel calcium mediated caspase activation pathway during regeneration, which we are now working to define on a molecular level as part of our continued and productive collaboration with Prof. Monica Driscoll (Rutgers University).
Lesion conditioned neuronal regeneration in C. elegans
Tragically, mammals display weak neuronal regeneration within the central nervous system following traumatic neuron damage. One of the most exciting discoveries in neurotherapeutics is that mammalian neurons can strongly regenerate their central axons into and beyond an injury site if a conditioning lesion is made on their peripheral sensory axons. This lesion conditioning effect has been studied in mammals for several decades, yet is still relatively poorly understood. Employing subcellular-resolution femtosecond laser ablation we observe a strong lesion conditioning effect in the sensory neurons of C. elegans. Ablation of the sensory dendrite conditions the neuron for axon regeneration that would usually be lacking. Thus, we are establishing C. elegans as a novel model system for the study of lesion conditioning, with the goal of defining specific molecular pathways that modulate it.
Damage and recovery of small neuronal circuits
Acute laser severing of specific target neurons within the simple C. elegans nervous system presents a unique opportunity to study damage response and homeostasis within a completely mapped neuronal circuit in vivo. Within this context, we have made provocative findings by focusing on the beautifully simple circuit controlling the C. elegans touch reflex. Laser severing of either the anterior or posterior mechanosenory neurons results in an initial hyperactivation of the downstream circuitry and elevated execution of touch avoidance behaviors (i.e. bouts of reverse or increased forward movement). Over time the animal recovers and its behavior returns to its original baseline level. Employing automated computer tracking of C. elegans behavior, fluorescent calcium imaging of neuronal activity, optogenetic stimulation of circuit components and genetic analyses of relevant neuronal modulators, we are elucidating the molecular and network signaling mechanisms that facilitate this level of homeostatic plasticity within a very simple neuronal circuit following laser damage. Neuronal damage and sensory deprivation are known to elicit hyper-excitability and neuronal remodeling within the mammalian central nervous system. Prominent examples include phantom pain of amputated limbs, acute seizures and epilepsy resulting from traumatic brain damage and cortical rewiring after spinal cord injury or sensory deprivation. Employing the simple C. elegans nervous system, its powerful genetic techniques and our unique biophotonic capabilities, we are shedding new light on the mechanisms of homeostatic plasticity and network modulation following neuronal damage.
Chung S., Schmalz A, Ruiz R.C., Gabel C.V.#, Mazur E. “Femtosecond Laser Ablation Reveals Antagonistic Sensory and Neuroendocrine Signaling that Underlie C. elegans Behavior and Development.” Cell Reports, 4(2):316-26. doi: 10.1016/j.celrep.2013.06.027, 2013 (#corresponding author)
Chung S., Sun L., Gabel C. V., “In vivo neuronal calcium imaging in C. elegans”, Journal of Visualized Experiments (JoVE), 10;(74). doi: 10.3791/50357, 2013
Kim E., Sun L., Gabel C. V., and Fang-Yen C., “Long-term imaging of Caenorhabditis elegans using nanoparticle-mediated immobilization”, PLoS ONE 8(1): e53419. doi:10.1371/journal.pone.0053419, 2013
Pinan-Lucarre B.*, Gabel C. V.*#, Reina C. P., Hulme S. E., Shevkoplyas S. S., Slone R. D., Xue1 J., Qiao Y., Weisberg S., Roodhouse K., Sun L., Whitesides G. M., Samuel A. D. T.#, Driscoll M. “The Core Apoptotic Executioner Proteins CED-3 and CED-4 Promote Initiation of Neuronal Regeneration in Caenorhabditis elegans”, PLoS Biology, 10(5):e1001331, 2012 (* co-first authors, #corresponding authors)
Hulme S. E., Gabel C. V. and Shevkoplyas S. S., “A Microfluidic Tool for Immobilizing C. elegans”, in “Microdevices in Biology & Medicine”, Nahmias Y. and Bhatia S. N., eds., Artech House, Boston, 2009
Gabel C. V., “Femtosecond Lasers in Biology: Nanoscale Surgery with Ultrafast Optics”, review article, Contemporary Physics, 49(6): 391-411, 2008
Gabel C. V., Antoine F., Chuang C., Samuel A. D. T., Chang C., “Distinct Cellular and Molecular Mechanisms Mediate Initial Axon Development and Adult-Stage Axon Regeneration in C. elegans”, Development, 135: 1129-1136, 2008
Gabel C. V., Gabel H., Pavlichin D., Kao A., Clark D. A., Samuel A. D. T.. “Neural Circuits Mediate Electrosensory Behavior in Caenorhabditis elegans”, J. Neuroscience 27(28): 7586-7596, 2007
Clark D. A., Gabel C. V., Gabel H., Samuel A. D. T., “Temporal Activity Patterns in Thermosensory Neurons of Freely Moving C. elegans Encode Spatial Thermal Gradients”, J. Neuroscience 27(23): 6083-6090, 2007
Clark D.A.*, Gabel C. V.*, Lee T. M., Samuel A., “Short-term Adaptation and Temporal Processing in the Cryophilic Response of Caenorhabditis elegans”. J Neurophysiol. 97(3): 1903-1910, 2007 (* co-first authors)
Biron D., Shibuya M., Gabel C., M. Wasserman S. M., Clark D. A., Brown A., Sengupta P., and Samuel A. D. T., “A Diacylglycerol Kinase Modulates Long-Term Thermotactic Behavioral Plasticity in C. elegans”, Nature Neuro, 9(12): 1499-1505, 2006
Chung S. H., Clark D. A., Gabel C. V., Mazur E., Samuel A. D. T., “The Role of the AFD Neuron in C. elegans Thermotaxis Analysed Using Femotsecond Laser Ablation”, BMC Neuroscience, 7:30, 2006
Gabel C. V. & Berg H. C., “The Speed of the Flagellar Motor of Escherichia coli Varies Linearly with Protonmotive Force”. Proc. Natl. Acad. Sci. USA, 100: 8748-8751, 2003
Gifford S. C., Frank, M. G., Dergan J., Gabel C., Austin R. H., Yoshida T., Bitensky M. W., “Parallel Micro-channel Based Measurement of Individual Ethrocyte Areas and Volumes”. Biophys. J. 84(1): 623-633, 2003
Carlson R. H., Gabel C. V., Chan S. S., Austin R. H., Brody J. P., Winkelman J.W., “Self-sorting of White Blood Cells in a Lattice”, Phys Rev Lett, 79: 2149-2152, 1997
If you are interested in joining our group, please inquire at the address below.
Department of Physiology and Biophysics
Boston University School of Medicine
700 Albany Street
Boston MA 02118-2526
Fax: (617) 638-4273