Project 1
-
Brain function & Synaptic
transmission
Neurotransmitter release is a key process for
intercellular communication in the brain. Fatt and Katz (1952) first
proposed the vesicular nature (‘quanta’) of neurotransmitter release at
the presynaptic terminal on the basis of their electrophysiological
observation. The following electron microscopy studies revealed structural
identity of synaptic vesicles (Cowan, Shdhof & Stevens, 2001). This vesicle
hypothesis of neurotransmitter release was further confirmed when vesicles
containing neurotransmitters were biochemically purified (Whittaker,
1968). During the last decade, major molecular components important in
synaptic release of neurotransmitter have been identified using model
animals such as C. elegans, Drosophila and mice. Physiologically, regulated neurotransmitter release is important
for short-term and long-term synaptic plasticity mediating learning and
memory. A key challenge in modern neurobiology is to understand the
essential molecular framework and its dynamics underlying synaptic vesicle exocytosis and
regulated release of neurotransmitter in the central nervous system.
Project title:
Neurotransmitter
release at Drosophila central synapses
[click here
for the
detailed description]
Why is Drosophila?
In our study, we have chosen to utilize the fruit fly Drosophila
melanogaster as a model animal to study synaptic transmission
mediating higher brain function. This small creature is almost meaningless
for your daily activities. However, in biological prospect,
Drosophila has been exceptionally valuable for molecular genetic
studies in understanding role of single genes in a variety of biological
processes such as early development. Since Drosophila also exhibits
well-characterized behaviors such as, learning and memory, courtship and
motor behaviors, and circadian rhythm, several single genes important in
mediating these complex behaviors were identified. A few examples of
isolated genes are dunce, rutabaga, amnesiac, dCREB, fruitless, and
so on.
Some of these genes were further studied to examine their roles in
regulating synaptic transmission using Drosophila neuromuscular
junction (NMJ). Since the NMJ is electrophysiologically accessible to
measure current and membrane potential changes, this peripheral
glutamatergic synapse (NMJ) has been extremely important in understanding
structural and functional bases of synaptic communication using genetic
mutants showing defects in behaviors. What we don’t know, however, is how
these single genes are regulating neurotransmitter release in the
Drosophila central nervous system (CNS). This information is necessary
to understand molecular and cellular mechanisms underlying the complex
behaviors. The goal of our study is to examine the role of the single gene
and signaling molecules regulating synaptic transmission, plasticity and
modulating in the CNS.
Project
2 -
Brain degeneration & Parkinson's
disease
Since the synapse is a
functional building block of the brain, defects in, or loss of, specific
synaptic signaling/modulation consequently underlies neurological
disorders such as Parkinson’s disease (PD). Therefore, our interests are
to understand the cellular and molecular mechanisms underlying selective
degeneration of dopaminergic (DA) neurons and synapses. Among the proposed
underlying causes of DA cell death, oxidative damage is thought to play an
important role. Ironically, neurotransmitter dopamine itself can become a
source of oxidative stress and consequently contribute to the selective DA
cell death in PD. This study aims to reveal mechanisms underlying
dopamine’s ability to mediate a-synuclein-induced
neurodegeneration. We will employ molecular genetic, immunocytochemical
and amperometrical approaches applied to a variety of transgenic fly lines
and primary neuronal cultures as a model system. The results of our
experiments will contribute to our understanding of the molecular
mechanisms of how a-synuclein induces disruption of DA homeostasis,
resulting in elevated levels of cytoplasmic DA and eventually leading to
specific neuronal death. The high degree of conservation between
vertebrates and invertebrates in terms of the basic mechanisms important
in DA modulation, suggests that our studies in Drosophila will be
important in guiding development of rational treatment strategies aimed at
restoring dopamine function/homeostasis that has been disrupted in
Parkinson’s disease patients.
Project title:
Role
of dopamine in alpha-Syn-mediated neurodegeneration
[click here
for the
detailed description]
Why is Drosophila for
Parkinson's Disease research?
Parkinson’s disease is complicated and
develops in such a slow fashion that we can not easily use human subjects
to study its molecular and cellular pathogenesis. An alternative is to use
model animals, suitable for molecular and cellular manipulations. In
addition to several vertebrate models, the fruit fly Drosophila
melanogaster has been recently proven to be useful in studies of the
mechanisms underlying neurodegenerative diseases (Muqit & Feany, 2002;
Bonini & Fortini, 2003) due to its powerful and sophisticated genetics.
Indeed, an intriguing PD model has been developed by engineering
transgenic flies that express the human
a-Syn
protein (Feany & Bender, 2000). These animals exhibit typical anatomical
and behavioral symptoms of PD, including an age-dependent loss of DA
neurons in addition to filamentous inclusion of Lewy bodies and locomotor
dysfunction. We also observed age-dependent DA cell loss in neuronal
cultures prepared from these a-Syn
transgenic flies. Therefore, Drosophila neuronal culture provides a
unique model system for PD research since it can take advantage of
sophisticated molecular genetic approaches in addition to easy
pharmacological and biochemical manipulations. In this proposal, we will
examine the mechanisms underlying dopamine’s ability to both induce and
prevent DA cell death.
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