The Neuromuscular Junction Acetylcholine Receptors (Red), Synaptic Vesicles (Green), Axoplasm (Blue)
A main focus of the lab is to identify molecular factors that maintain and repair the neuromuscular junction, the synapse formed by motor neurons and skeletal muscle fibers. As the final output of the nervous system, this synapse regulates all voluntary movements. Unfortunately, this synapse is severely affected by the normal aging process, diseases and injury. Our hope is that molecules that we discover can be used to develop therapeutic agents to maintain the well-being of this synapse. The lab is currently working on the following projects:
1- The roles of muscle microRNAs in regulating stress responses at the NMJ.
2- The function of a subset of fibroblast growth factors, FGF-7/10/22 and their binding protein FGFBP1, in maintaining and repairing the NMJ.
3- The impact of motor activity at the NMJ during the progression of amyotrophic lateral sclerosis and aging.
4 – Identification of additional molecular mechanism – those likely recruited by life-style factors such as exercise and caloric restriction – that cooperate to maintain and repair the NMJs.
We also have a vested interest in understanding changes in other synapses, particularly those formed on motor neurons in the spinal cord and between different neuronal populations in the hippocampus. In the spinal cord, we examine changes at synapses formed between proprioceptive sensory neurons and motor neurons. In the brain, we are studying the role of circadian genes in the formation and maintenance of synapses. Ongoing projects include:
1- Examination of proprioceptive connections with motor neurons in aged and ALS-afflicted mice.
2- The effect of modulating cholinergic levels on the spinal cord circuits.
3- Function of circadian genes during synaptogenesis and in maintaining neuronal connections.
4- Roles of circadian genes in epileptic seizures.
A neuron growing on a patterned substrate
Biochemical and Molecular Approaches
We use a variety tools and techniques to discover molecules needed to maintain and repair synapses. In most of our experiments, we use imaging techniques examine structural changes at synapses. We then use cell culture, biochemical and genetic tools to discover molecules that drive changes at synapses. Techniques routinely used in the lab include:
1- Live and static imaging of cells and synapses using confocal and epifluorescence microscopy.
2- Analysis of neurons and muscles in cultures.
3- Isolation of ribosomes from subsets of neurons for transcriptome analysis.
In many of our projects studying the function of genes in mice, we first start with behavioral and performance tests to determine the broad impact of modifying the gene of interest or pharmacological intervention on the whole organism. We then use behavioral data to better design experiments aimed at studying changes at specific synapses.
1 – Running wheels: to determine the pattern and level of activity in mice.
2- Rotarod testing: to test the sensorimotor system of animals.
3- Water Maze: tests a variety of neuronal systems, including the motor system and the hippocampus.
Mouse on a running wheel
We have developed a bioinformatics platform, EvoCor, to more efficiently and cheaply identify genes that function together. Using this platform and a known gene, we can generate a list of candidate genes to validate their expression and function in the lab. EvoCor: http://pilot-hmm.vbi.vt.edu
James Dittmar is the lead author of a recently published paper in the journal NAR describing the implementation of EvoCor.