Fumihito Ono, M.D., Ph.D., Acting Chief
Jee-Young Park, PhD, Postdoc Fellow
Hiromi Ikeda, PhD, Postdoc Fellow
Meghan Mott, PhD, Postdoc Fellow
Vivek Gupta, Summer Intern
Nao Kawahori, Special volunteer

Staff Photo of the Section on Model Synaptic Systems


 

Mission Statement

The goal of MSS is to clarify basic mechanisms of neuronal functions, particularly in the context of substance abuse, such as alcohol or nicotine. We use a genetic model system, zebrafish, in our study. By introducing modified forms of proteins into mutant fish with abnormal behaviors, we can change their behavior or monitor the cellular activity in semi-intact animals. Thanks to the rapid and external development of zebrafish, neural mutants survive long enough to allow analysis of neural functions before they die. The transparency of zebrafish embryos also enables an optical observation. These unique features of zebrafish present a valuable opportunity to study nervous system in vivo.

 

Current Projects

The Section on Model Synaptic Systems started in 2007, when Fumihito Ono moved to NIH/NIAAA from the University of Florida. We are currently studying the nervous system at several levels. An experimental paradigm we have used heavily for the past several years is the neuromuscular junction (NMJ), which is a synapse between motor neuron and muscle. Not only is this synapse directly linked to various diseases arising from genetic defects or autoimmune conditions, it also offers an exceptional accessibility for an array of experimental techniques. We have recently broadened our scope of research and are also studying neural networks in the central nervous system and its response to ethanol.

 

Neuromuscular junction as a model system of nicotinic synapse

Our projects on NMJ center around locomotion mutants we discovered to have defects in two key molecules of the neuromuscular synapse. One mutant lacks acetylcholine receptors (AChR) in the muscle. As a result, the fish cannot mount a movement when the motor neuron releases ACh. Another mutant has a dysfunctional rapsyn. Rapsyn is a post-synaptic protein that brings AChRs together. In this fish, AChRs do not make clusters at the synapse and are diffusely distributed over the muscle cell surface.

AChR was traditionally considered a passive player in the synapse formation. In a recently published study, however, we revealed an active role of AChR: it enables the transport of rapsyn molecule from the Golgi complex to the plasma membrane (Park et al., 2012). Using an AChR mutant newly identified in collaboration with Dr. Paul Brehm at OHSU, we are further pursuing the mechanism of synapse formation.

AChR-less fish has an analogous disease in human, which is called Fetal Akinesia Deformation Sequences (FADS). Human embryos that harbor mutation in one of the AChR genes suffer premature death in the first trimester. We introduced a modified AChR gene into the mutant fish. The introduced gene expressed in all muscle cells, which led to a successful rescue of the mutant fish. The rescued fish survives well beyond sexual maturation, and they can mate normally, producing offspring. To the best of our knowledge, this is the first case of a mutant animal corresponding to the first trimester lethality in human that has been rescued by a transgene and survived to adulthood (Epley et al., 2008). When the AChR expression was delayed by a chemically-inducible expression system, however, myasthenic swimming and presynaptic deficiency was observed, in spite of the formation of anatomically normal post-synaptic clusters. These results show the potential of gene therapy for myasthenic diseases and highlight the importance of the timing of gene expression for the full rescue. We are investigating the molecular mechanism underlying the phenomenon.

 

Response of neurons to ethanol

We also study effects of ethanol on the zebrafish brain, by analyzing intoxicated embryos at the cellular level. We analyzed intrinsic properties of neurons in ethanol, and found that individual neurons in larval zebrafish brains have distinct patterns of response to ethanol, dictated by specific molecular targets.

 

Publications at NIH (2007-)

Ono, F. (2012) Big answers from a small fly with a cultured brain. Journal of Physiology in press.

Walogorsky, M., Wen, H., Mongeon, R., Urban, J., Ono, F., Mandel, G., Brehm, P. (2012) A zebrafish model for congenital myasthenic syndrome reveals mechanisms causal to developmental recovery. Proceedings of the National Academy of Sciences 109: 17711-17716.

Won, Y., Ono, F., Ikeda, S. (2012) Characterization of Na+ and Ca2+ channels in zebrafish dorsal root ganglion neurons. PLoS ONE 7: e42602.

Papke, R., Ono, F., Stokes, C., Urban, J., Boyd, T. (2012) The nicotinic acetylcholine receptors of zebrafish and an evaluation of pharmacological tools used for their study. Biochemical Pharmacology 84:352-365.

Park, J., Ikeda, H, Ikenaga, T., Ono, F. (2012) Acetylcholine receptors enable the transport of rapsyn from the Golgi complex to the plasma membrane. Journal of Neuroscience 32:7356-7363.

Nakayama, S., Ikenaga, T., Kawakami, K., Ono, F., Hatta, K. (2012) A Gal4 gene trap line useful for studying the morphogenesis of craniofacial perichondrium, vascular endothelium-associated cells, floor plate, and dorsal midline radial glia during zebrafish development. Development Growth and Differentiation 54: 202-215.

Mongeon, R., Walogorsky, M., Urban, J., Mandel, G., Ono, F., Brehm, P. (2011) An acetylcholine receptor lacking both g and e subunits mediates transmission in zebrafish slow muscle synapses. Journal of General Physiology 138: 353-366.

Ikenaga, T., Urban, J., Gebhart, N., Hatta, K., Kawakami, K., Ono, F. (2011) Formation of the spinal network in zebrafish determined by domain-specific Pax genes. Journal of Comparative Neurology 519: 1562-1579.

Diep, C., Ma, D., Arora, N., Wingert, R., Bollig, F., Djordjevic, G., Lichman, B., Zhu, H., Ikenaga, T., Ono, F., Englert, C., Hukriede, N., Handin, R., Davidson, A. (2011) Identification of adult renal progenitor cells capable of nephron formation and regeneration in zebrafish, Nature 470: 95-100.

Won, Y., Ono, F., Ikeda, S. (2011) Identification and modulation of voltage-gated Ca2+ current in zebrafish Rohon-Beard neurons, Journal of Neurophysiology 105: 442-453.

Epley, K., Urban, J., Ikenaga, T., and Ono, F. (2008) A modified acetylcholine receptor d-subunit enables a null mutant to survive beyond sexual maturation.  Journal of Neuroscience 28: 13223-13231.

Ono, F. (2008) An emerging picture of synapse formation: A balance of two opposing pathways. Science Signaling 1, pe3.

 

Alumni

Nichole Gebhart (Graduate student): Clinical research coordinator, University of Pennsylvania.

Kimberly Epley (Postdoc): Director of regional development, Case Western Reserve University, School of Medicine.

Takanori Ikenaga (Postdoc): Assistant professor, Department of Biology, University of Hyogo, Japan.

Alison Delargy (Postbacchalaureate): Student, Osteopathic Medicine, University of New England.

Jason Urban (Postdoc): Staff fellow, Food and Drug Administration.