Robert Siman, Ph.D.
Research Associate Professor of Neurosurgery
Member, Institute of Neurological Sciences
Member, Center for Brain Injury and Repair
Member, Institute for Translational Medicine and Therapeutics
Department: Neurosurgery
Contact information
Department of Neurosurgery
502 Stemmler Hall
36th and Hamilton Walk
Philadelphia, PA 19104
502 Stemmler Hall
36th and Hamilton Walk
Philadelphia, PA 19104
Office: 215-573-6245
Fax: 215-898-9217
Fax: 215-898-9217
Email:
siman@mail.med.upenn.edu
siman@mail.med.upenn.edu
Graduate Group Affiliations
Publications
Education:
B.A. (Biology)
University of Pennsylvania, 1976.
Ph.D (Neurobiology)
Northwestern University, 1981.
B.A. (Biology)
University of Pennsylvania, 1976.
Ph.D (Neurobiology)
Northwestern University, 1981.
Post-Graduate Training
Postdoctoral Fellow, Department of Psychobiology and Center for the Neurobiology of Learning and Memory, University of California, Irvine, CA, 1981-1985.
Permanent linkPostdoctoral Fellow, Department of Psychobiology and Center for the Neurobiology of Learning and Memory, University of California, Irvine, CA, 1981-1985.
Description of Research Expertise
Research SummaryRecent advances in cell biology and genetics have led to an explosion of information about intracellular signaling mechanisms for nerve cell death, and the identification of gene mutations responsible for inherited forms of many neurodegenerative diseases. There are, however, several challenges for converting these advances in basic neurobiology to new and effective treatments. Toward meeting these challenges, my laboratory is identifying specific cell death signaling pathways that underlie particular neurodegenerative processes in the brain, defining pathogenic mechanisms by which disease-causing mutations impact these signaling pathways, and devising non-invasive surrogate markers for detecting distinct modes of neurodegeneration in the brains of living organisms.
Our signaling work focuses on brain proteases, now recognized as critical mediators of both apoptotic and necrotic modes of neuronal death, as well as the abnormal protein aggregation that is a pathological hallmark of Alzheimer’s and other neurodegenerative disorders. The laboratory developed an antibody-based technology known as protease fingerprinting for measuring activation of specific proteases, localizing their activation at the anatomical level, and identifying their protein substrates that are potential downstream effectors of cell death signaling. Protease fingerprinting has also led to the identification of surrogate markers that are measurable in cerebrospinal fluid and serum following brain injury in both experimental animals and human patients, and indicate the magnitude of the brain damage, the underlying signaling mechanisms involved, and the efficacy of candidate neuroprotective treatment regimens. By developing a panel of such markers for neurodegeneration along with immunoassays for their highly sensitive and specific quantitation, we aim to impact the diagnosis, prognosis, and treatment of acute brain injuries in numerous clinical settings.
Another focus has been the characterization of a faithful mouse genetic model of Alzheimer’s disease (AD), developed by “knocking in” disease-causing mutations in amyloid precursor protein and presenilin-1 into their endogenous mouse genes. We are using this disease model to understand how an imbalance in protease activities leads to abnormal protein accumulation, discern how protein aggregates impact forms of adaptive plasticity in neural pathways that are both critical for long-term memory and severely impacted in AD, and identify treatment strategies for reducing the pathology and restoring the neural plasticities.
Selected Publications
von Reyn CR, Spaethling JM, Mesfin MN, Ma M, Neumar RW, Smith DH, Siman R, Meaney DF: Calpain mediates proteolysis of the voltage-gated sodium channel alpha-subunit. J Neurosci 29: 10350-10356, 2009.Siman, R., Toraskar, N., Dang, A., McNeil, E., McGarvey, M., Plaum, J., Maloney, E., Grady, M.S.: A Panel of Neuron-Enriched Proteins as Markers for Traumatic Brain Injury in Humans. J Neurotrauma 26: 1817-1827, 2009.
Siman R, Roberts VL, McNeil E, Dang A, Bavaria JE, Ramchandren S, McGarvey M.: Biomarker evidence that surgically-induced circulation arrest elicits central nervous system injury. Brain Res 1213: 1-11, 2008.
Zhang C, McNeil E, Dressler L, Siman R.: Long-lasting impairment in hippocampal neurogenesis associated with amyloid deposition in a knock-in mouse model of familial Alzheimer's disease. Exp Neurol 204: 77-87, 2007.
Serbest G, Burkhardt MF, Siman R, Raghupathi R, Saatman KE.: Temporal profiles of cytoskeletal protein loss following traumatic axonal injury in mice. Neurochem Res 32: 2006-2014, 2007.
DeRidder MN, Simon MJ, Siman R, Auberson YP, Raghupathi R, Meaney DF: Traumatic mechanical injury to the hippocampus in vitro causes regional caspase-3 and calpain activation that is influenced by NMDA receptor subunit composition. Neurobiol Dis 22: 165-176, 2006.
Lawrence EJ, Dentcheva E, Curtis KM, Roberts VL, Siman R, Neumar RW: Neuroprotection with delayed initiation of prolonged hypothermia after in vitro transient global brain ischemia. Resuscitation 64: 383-388, 2005.
Siman R, Zhang C, Roberts VL, Pitts-Kiefer A, Neumar RW: Novel surrogate markers for acute brain damage: Cerebrospinal fluid levels corrrelate with severity of ischemic neurodegeneration in the rat. J Cereb Blood Flow Metab 25: 1433-1444, 2005.
Bakshi A, Keck CA, Koshkin VS, LeBold DG, Siman R, Snyder EY, McIntosh TK: Caspase-mediated cell death predominates following engraftment of neural progenitor cells into traumatically injured rat brain. Brain Res 1065: 8-19, 2005.
Strachan GD, Koike MA, Siman R, Hall DJ, Jordan-Sciutto KL: E2F1 induces cell death, calpain activation, and MDMX degradation in a transcription independent manner implicating a novel role for E2F1 in neuronal loss in SIV encephalitis. J Cell Biochem 96: 728-740, 2005.


