Survival and Death Regulation of Neurons
and Brain Tumor Cells
Apoptosis, or programmed cell death (PCD),
is a fundamental biological process that is
required for normal development and tissue
homeostasis. Complex regulatory pathways
control cell death process that is
intricately linked to other cellular
processes such as cell proliferation,
differentiation, and tumorigenesis.
Deregulation of apoptosis plays a major role
in various diseases including
neurodegenerative disorders and cancer.
Understanding the molecular mechanism
controlling cell survival and death thus
holds great promise for designing treatment
strategies for cancer and neurodegenerative
diseases, ranging from Alzheimer's disease,
Parkinson's disease, amyotrophic lateral
sclerosis, and stroke.
The focus of our laboratory is to understand
the signaling mechanisms that control death
of neurons and cancer cells. Our work has
established that silencing of E2F responsive
genes are required for neuron survival and
that apoptotic stimulation leads to
activation of cell cycle elements that
promote E2F de-repression and neuron death.
Our studies have further demonstrated that
E2F-responsive apoptotic genes are silenced
by E2F4-p130-Suv39H1-HDAC complexes in
unstressed neurons and that apoptotic
stimulation leads to CDK-dependent
phosphorylation of p130, which results in
disassembly of the E2F4-p130-Suv39H1-HDAC
complexes on promoters of repressed
apoptotic genes. Among these de-repressed
apoptotic genes are transcription factors B-
and C-myb. Elevation of B- and C-myb induces
pro-apoptotic Bcl-2 family member Bim,
provoking neuron death. One direction of our
future work is to identify other key
apoptotic genes that are controlled by the
E2F de-repression pathway in neurons. Our
lab uses interdisciplinary approaches
including cellular, molecular, genetic, and
biochemical techniques to dissect the
apoptotic mechanisms used by neurons and
cancer cells and to isolate novel proteins
critical for regulation of cell death in
those cells. We also use the same techniques
to investigate how neural stem cells, such
as telencephalic neuroprogenitor cells, are
maintained and what promote their
differentiation and survival.
The current research projects in our
laboratory are centered on the following
three topics:
1) Cell cycle machinery and neuronal cell
death. We are particularly interested in
understanding the involvement of the
CDK-Rb-E2F axis, a central cell cycle
pathway in regulating cell proliferation in
dividing cells, in regulation of neuronal
cell death. Published work in this area
includes Liu et al., Genes&Dev. 19:719-32,
2005; Liu et al., J. Neurosci. 24:8720-5,
2004; Liu and Greene, Neuron 32:425-38,
2001.
2) Delineation of the signal transduction
pathways that implicate ATF5 in regulation
of brain tumor cell survival. Relevant work
includes Angelastro et al, Oncogene
25:907-16, 2006.
3) Regulation of neural stem cells. We are
interested in understanding how ATF5 blocks
cell cycle exit and maintains "stemness" of
neural stem cells in the developing brain.
Using in utero gene transfer technique, we
are able to study gene function in vivo
during mammalian neurogenesis (see Graphic
explanation below). We also want to learn
how to control the differentiation process
that turns a neural stem cell into a
particular type of neuron or glia cell, a
process called "directed differentiation".
Our laboratory is making exciting
discoveries in a number of frontiers, where
both post-doctoral fellows and pre-doctoral
students who seek biological research as a
component of their career may find excellent
training opportunities. As a part of that,
one can learn a variety of experimental
techniques and use them to address
fundamental biological questions. These are
techniques that we have successfully used in
our previous and current work, including,
e.g., gene cloning and mutagenesis, DNA and
RNA preparation and quantitative real-time
PCR, protein-protein interaction, protein
phosphorylation status and functioning
analysis, cell culture-related preparation,
maintenance and transfection of primary
neurons, stem cells and a variety of cell
lines, biochemical assays such as luciferase
and beta-gal reporter assays and kinase
assay, in vitro translation, various
survival assays, anti-sense and siRNA gene
knock-down, Western blotting,
co-immunoprecipitation (IP), subcellular
fractionation, ubiquitination analysis,
immunohistochemistry (IC),
immunofluorescence (IF), electrophoretic
mobility shift assay (EMSA), and chromatin
immunoprecipitation (ChIP).
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