Mission Statement:

Our goal is to clarify basic principles of synapse function by using a genetic model system, zebrafish. We use mutant fish with abnormal behaviors. By introducing modified forms of neural proteins into these fish, we can change their behavior. 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: in vivo observation of genetically marked neural proteins, in particular. These unique features of zebrafish present a valuable opportunity to study the developing nervous system in vivo.

Current Staff:

Principal Investigator

Fumihito Ono, M.D., Ph.D.

TS32, 5625 Fishers Lane, Rockville, MD. 20852
Office: 301-443-3748
Lab: 301-443-3772
Fax: 301-480-0466
email: onof@mail.nih.gov

Postdoctoral Fellow

Jason Urban, Ph.D.
Takanori Ikenaga, Ph.D

Postbaccalaureate Fellow

Alison Delargy, B.A.

Alumni

Postdoc
Kimberly Epley

Graduate Student
Nicole Gebhart

Undergraduate
Elizabeth Jimenez
Dana Smith
Meghan Mott
Jarrod Smith

Current Projects:

Our projects center around locomotory 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. From the AChR-less mutant, we found that AChR plays an active role, directing rapsyn molecules to synapse. In rapsyn mutant fish, we found that AChRs not only fail to form clusters at synapse, but also their functions are altered. When motor neurons fire at a high frequency, the amplitude of AChR current remains constant in wild type, whereas in rapsyn-mutant fish the response shows a marked attenuation with repeated firing of motor neurons. Several projects aim to figure out the mechanisms underlying these unexpected functions of AChR and rapsyn. Expression of AChR or rapsyn fused to fluorescent proteins allows us to visualize these proteins as they work in synapses. Genetic modification of these proteins in mutant background clarifies the molecular mechanism that work in the process.

These locomotion mutants also provide a unique opportunity to study functions of AChRs expressed in the cenral nervous systems (CNS), which play important roles in various nervous system disorders including alcoholism. In the neuromuscular synapse of AChR-less mutant, we showed that pre-synaptic machinery releasing ACh develops normally. These AChR-less mutants therefore allow us to study brain-type AChRs in a real synapse context, when the receptors are ectopically expressed in the muscle cells. We are using this "model synapse" to study functions of CNS receptors, which is difficult to study in its native environment.

In a separate set of projects, we are performing several forward genetic screenings on zebrafish. A transgenic zebrafish isolated from a screening expresses red fluorescent protein (RFP) in a sub-population of neurons. In these neurons, the expression of a transcription factor is replaced by RFP. Use of this and other lines of fish allow us to study functions of developmental genes in living animals. Information gained from these studies will help to clarify basic principles of neural activity and connectivity.


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Updated: December 2008