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Christine E. Beattie , Ph.D.
Associate Professor
The Ohio State University
Center for Molecular Neurobiology
Department. of Neuroscience
190 Rightmire Hall
1060 Carmack Rd
Columbus, Ohio 43210
Phone: (614) 292-5113
Fax: (614) 292-5379
Email:
beattie.24@osu.edu
Education & Training:
Case Western Reserve University, 1987 B.S. in Biochemistry,
Case
Western Reserve University, 1992 Ph.D.
University of Oregon, Eugene,
1997 Postdoctoral Fellow
Research Interest:
A major focus of the lab is investigating the biological basis
of motoneuron diseases. In particular, we focus on two human motoneuron
diseases, spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis
(ALS). For our studies, we use zebrafish as a vertebrate model organism
due to its well characterized nervous system and its relatively simple
neuromuscular organization. Our goal is to develop zebrafish models of
these disease to gain in sight into disease mechanism and to develop drug
and genetic screens as a way to identify effective therapeutics.
What is the biological basis of the motoneuron diseases Spinal Muscular
Atrophy (SMA)?
Our understanding of the genetics and development of motoneurons
puts us in an excellent position to address the biological basis of motoneuron
diseases. Currently, we are establishing zebrafish as a model of Spinal
Muscular Atrophy (SMA); a motoneuron degenerative disease caused by mutations
in the survival motoneuron gene (smn). SMA is caused
by low levels of the SMN protein. Although the ubiquitously expressed
Smn protein has been implicated in snRNP (RNA and protein) complex essential
for mRNA splicing, it remains unclear why low Smn levels specifically
compromises motoneurons. Using protein knockdown technology (anti-sense
morpholinos), we decreased the amount of Smn present during zebrafish
development and found dramatic defects in motor axon outgrowth and guidance.
In particular, motor axons were truncated and excessively branched. By
decreasing Smn in single motoneurons in living embryos, we found that
Smn functions cell-autonomously with respect to motoneurons in this process.
This data suggests that Smn is needed for normal motoneuron development. We
also showed that more severe motor axon defects caused decreased longevity
and disruptions at the neuromuscular junction (NMJ). A central
question in SMA is what function of SMN, when disrupted, leads to motoneuron
dysfunction and disease. SMN has a well-characterized role in splicing,
but data has also suggested that it could function in other ways in cells
perhaps to assembly mRNA and proteins for transport and localized protein
translation. To get at this, we asked what forms of Smn could rescue
these motor axon defects. Using human SMN RNA we tested a number
of both patient and synthetic mutations and co-injected these with the smn MO. We
found that wild-type hSMN could rescue the motor axon defects, but no
patient mutations could rescue when added at the same dose. Testing
a number of different SMN forms, we found that SMN forms that had their
snRNP properties in tact, could still not rescue the motor axon defects
caused by low Smn. These studies suggest that for normal motor
axon development that perhaps some other function beside snRNP is necessary.
To further investigate this possibility, we have generated a genetic
model of SMA in zebrafish that will allow us to perform more detailed
and long range studies.
Modeling ALS in zebrafish
Amyotrophic lateral sclerosis is an
adult onset, fatal, motoneuron degenerative disease that has no cure
and limited therapies. While the majority
of ALS cases have no known genetic component, 1-2% are caused by mutations
in the SOD1 gene. Changes in 74 of the 154 amino acid protein
causes a form of ALS indistinguishable from sporadic ALS thus serving
as a way to model ALS in animals. To date, only a mouse model of
SOD1 ALS has been generated. Major questions regarding the toxicity of
the mutant SOD1 forms, how they cause motoneuron death, where they are
functioning, and what genetic pathways they act in remain unanswered. As
there are no reported examples of ALS models in invertebrates, only rodent
models of this disease exist thus limiting the type of experiments that
can be performed. For example, although it is possible to map modifier
genes that affect FALS, it is not possible to do modifier screens in
mice. Using the zebrafish Sod1 gene, we have generated Sod G93A and G85R
transgenic zebrafish. Two independent lines of G93A express mutant
protein in brain and spinal cord at levels ~3-fold higher than wild type
Sod. We
used confocal microscopy to show that the fish display neuromuscular
junction defects suggestive of muscle denervation. This is confirmed
by electron microscopy (EM) showing both muscle and motoneuron degeneration. Since
we were seeing defects in the neuromuscular system, we wanted to test
the strength of the muscle. We did this by testing fish in a current
swim tunnel. Using this approach we found that the transgenic lines over
expressing mutant Sod protein, were unable to swim in strong currents
like wild-types indicating that they had muscle weakness. Our data suggest
that we have generated a new vertebrate model of ALS that will be useful
for studies of ALS biology and as a tool for drug and genetic screening.
Selected Publications:
- McWhorter, M. L., Monani, U.R., Burghes, A. H. M. and Beattie, C.
E. (2003) Knock-down of the Survival Motoneuron protein (Smn) in zebrafish
causes defects in motor axon outgrowth and pathfinding. The Journal
of Cell Biology 162: 919-931.
- Carrel, T. L., McWhorter, M. L., Workman, E. Zhang, H., Wolstencroft,
E. C., Lorson, C., Bassell, G., Burghes, A. H. M., and Beattie, C.
E.(2006) SMN function in motor axons is independent of functions required
for snRNP biogenesis. Journal of Neuroscience 26: 11014-11022.
Highlighted
in This Week in the Journal
- Beattie, C. E., Carrel, T. L, and McWhorter, M. L. (2007) Fishing
for a Mechanism: Using Zebrafish to Understand Spinal Muscular Atrophy. Journal
of Child Neurology 22: 995-1003.
- McWhorter, M. L., Boon, K., Horan, E. S., Burghes, A. H. M., and
Beattie, C. E. (2008)The SMN complex protein Gemin2 is not involved
in zebrafish motor axon outgrowth. Developmental Neurobiology:
68:182-94
- Oprea, G. E., Kröber, S., McWhorter, M. L., Rossoll, W., Müller,
S. Krawczak, M., Bassell, G. J., Beattie, C. E. and Wirth, B. Plastin 3
is a Protective Modifier of Autosomal Recessive Spinal Muscular Atrophy
(2008) Science: 320(5875):524-7.
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