Development of Lewy Bodies Biofluid Signatures by Targeted Proteomics (U18)
Lewy bodies are abnormal protein aggregates discovered by Frederic Lewy in 1912. Lewy bodies form in the nerve cells of Parkinson's disease patients and their presence along with loss of specific nerve cells, that make dopamine, in a region of the brain called the substantia nigra, have been used as signature signs of Parkinson's disease progression. Unfortunately, with current technology, the presence of Lewy bodies can only be evaluated after a person has died because it requires direct examination of the brain tissue under the microscope. Since the presence of Lewy bodies is one of the key signs of Parkinson's disease, Dr. Petyuk and his colleagues believe that being able to non-invasively detect Lewy bodies during a person's life, could be a way to measure Parkinson's disease progression. In addition, biomarkers that reflect the presence of Lewy bodies, could also be used to measure the usefulness of new drugs that may slow down disease progression. This research team will first figure out if there are any brain-specific proteins which are markers for the presence of Lewy bodies. They will then see if they can measure these proteins in biosamples such as cerebrospinal fluid (CSF) and/or blood -basically, biosamples that can be obtained from living individuals. If they can figure out what brain-specific proteins are associated with increasing Lewy body formation, and can measure those in CSF or blood, they will have a biomarker which could be very useful in clinical trials of neuroprotective agents (ie, medications that can protect the nervous system including the brain). Identification of these markers, could also be useful for diagnosing Parkinson's disease early, and, in differentiating Parkinson's disease from other closely-related disorders.
Parkinson's disease (PD) is the second most common age-onset neurodegenerative brain disorder. The disease manifests itself as complications with movement, and in about one third of the cases, is followed by cognitive impairment and dementia. The onset and severity of Parkinson's disease is associated with the presence and distribution of proteinaceous aggregates called Lewy bodies (LBs). Sadly, the presence of LBs can be determined only post-mortem by a pathologist. Therefore, we are proposing to develop an LB assay based on biofluid protein measurements. Our approach is based on two linked hypotheses. The first is that there are proteins and/or their post-translational modifications that increase in abundance in the presence of LBs. The second hypothesis is that proteins that infiltrate the cerebrospinal fluid and blood from the brain will be present in low abundances. Regardless the specific mechanism of brain to biofluid infiltration, we anticipate that it is a low efficiency process and requires highly sensitive proteomics approaches to detect specific neurons in the cerebrospinal fluid and especially in the blood. To test these hypotheses we have designed a two-stage study comprised of three objectives: 1) Discover brain tissue specific proteins and their modifications that correlate with the presence of LBs, using LC-MS proteomics data obtained for a group of 500 individuals from Religious Orders Study and Memory and Aging Project studies conducted by Rush University. Differentially abundant proteins exclusively expressed in the brain tissue will used for follow-up testing in biofluids. 2) Using ultra-sensitive selected reaction monitoring approach we will verify the correlation of abundances for these selected markers in the brain tissue and biofluids, including both cerebrospinal fluid and blood serum. We will then apply this information to develop a biofluid-based statistical model that predicts the LB load. 3) Validate the model by acquiring blood serum measurements for an independent PD case/control cohort based on the subjects enrolled into the Osteoporotic Fractures in Men Study.
Goals of Project
- Discovery: Identify proteins that correlate with the presence of the Lewy bodies (LB) in brain tissue. We will perform statistical analysis of quantitative LC-MS proteomics data that represents brain tissue samples of 500 subjects from the Religious Orders Study (ROS) and Memory and Aging Project (MAP) cohorts. Proteins that exhibit significant increases in abundance associated with the presence of Lewy bodies and are expressed exclusively in the brain tissue will be considered as biomarker candidates for subsequent verification in the CSF and blood.
- Discovery and Replication: Determine if the measured abundances of putative LB biomarkers in CSF and blood serum biofluids, correlate the results with brain tissue abundances (measured above) within the same subjects. These data will be used to develop a predictive model for LB presence.
- Replication: Test the blood-based LB predictive model using an independent PD case/control cohort. Protein biomarkers will be quantified in serum from 20 PD patients and matched controls available from the Osteoporotic Fractures in Men Study (MrOS) cohort. The predictions derived from the model will be matched against the clinical data to assess the agreement.
Presentation from the NINDS PDBP Kick-off Meeting in November 2012: Petyuk Project Kickoff Presentation (pdf)