Biomarkers of Disease
We use unbiased mass spectrometry-based proteomics to explore changes in the cerebrospinal fluid (CSF) proteome in ALS patients compared to other disease mimics and healthy control subjects. We have identified a number of individual proteins and specific cellular pathways that are altered in ALS patients. We are validating our findings in additional CSF samples collected at 30 medical centers in the United States and Canada. Our goal is to develop diagnostic biomarkers for ALS and to identify biochemical pathways that are altered early in disease.
We also have started a collaborative project to collect CSF and blood samples from ALS patients at the time of diagnosis and longitudinally as the disease progresses. We will assess the samples for biomarkers of ALS disease progression and prognostic indicators of the disease.
Amyotrophic lateral sclerosis, like other neurodegenerative diseases, is a heterogeneous disorder. This aspect of the disease makes finding effective treatments challenging. The best treatment will likely be a combination of drug therapies. If, however, we could identify subpopulations of ALS patients, it might be possible to create a more personalized approach to treatment. We are exploring methods to identify biomarkers that distinguish subpopulations of ALS patients. These biomarkers could be useful for targeting drug treatments to subpopulations that have a higher probability of responding to treatment.
Motor Neuron Cell Cultures as a Model of Neurodegeneration
To explore cell survival and death pathways in motor neurons, we use a primary motor neuron cell-culture model derived from rat spinal cords. We use these cells to examine specific biochemical pathways, to modulate signaling pathways via pharmacologic agents, or to express genes using viral vectors. Live cell-imaging approaches, coupled with fluorescence microscopy, are used to generate images and videos of motor neurons. Specific drug candidates are tested in the motor neuron cultures to assess their neuroprotective properties against excitotoxic or oxidative stress-induced neurodegeneration. We can also co-culture these motor neurons with glial cells or muscle progenitors/myotubes to explore cell-to-cell communications and the role other cell types play in modulating motor neuron cell death.
RNA Binding Proteins
Mutations in two RNA binding proteins (TDP-43 and FUS) cause familial forms of ALS. This fuding highlights the importance of normal RNA metabolism in the health of motor neurons. We have discovered additional RNA and DNA binding proteins that are altered in ALS patients. We are characterizing the function of these RNA binding proteins in motor neuron cell cultures and in patient-derived tissue samples. Specific mRNAs that interact with these RNA binding proteins will be determined by CLIP-seq or cross-linking immunoprecipitation followed by RNA sequencing. Protein-protein interactions will be determined by co-immunoprecipitation followed by mass spectrometry-based peptide sequencing. We will also determine if mutations in our RNA binding proteins occur in ALS patients.
Characterizing Cellular Pathways Using Human Tissue Samples
A vital resource and component of our research include the use of human tissue samples obtained postmortem from ALS patients and control subjects. We can determine the cell types that express specific proteins of interest and correlation between our protein of interest and the neuropathology that occurs during ALS. We collect post-mortem tissue samples from ALS and control subjects for use in our studies. We also collaborate with other clinicians and scientists across the country to generate a virtual tissue biorepository for ALS and to make tissue samples available for scientific investigations.
Translation to the Clinic
We have identified and will continue to search for potential drug candidates that are neuroprotective in our motor neuron cultures. We plan to continue the development of these drugs in human clinical trials. We also are using our biomarkers in ALS clinical trials to help rapidly determine if a particular drug is having a positive or negative effect on the patient. Our goal is to allow a more rapid go/no go decision regarding a drug in earlier phase clinical trials.