Dr. Walker’s current research focuses on using molecular tools, including whole-genome microarrays, to understand the biological basis for autism spectrum disorders (ASDs). Two of the keys deficits in the field of ASD research are: (1) a lack of biological/molecular diagnostic criteria to better define the disorder(s) and, (2) a lack of understanding of the biological mechanisms that underlie this complex set of disorders. Much of his research in this area involves understanding how chronic gastrointestinal (GI) symptoms in ASD children are involved in the overall disease phenotype, and in identifying surrogate (molecular) markers in blood of ASD children with GI symptoms in hopes of one day eliminating the need for colonoscopy in some children. He is involved in a number of studies in both human ASD children and in animal models that are designed to address these questions. A second focus of Dr. Walker’s research is to characterize transcriptomic profiles in cells going through various points in differentiation in an effort to better describe, through these RNA expression patterns, specific key events and characteristic profiles that define cellular status. As an example, we have used microarray profiling to show that animal oocytes do not appear to provide the signals necessary to reprogram human somatic nuclei (Chung et al., 2009).
Walker SJ, Fortunato J, Gonzalez LG, Krigsman A. Identification of unique gene expression profile in children with regressive autism spectrum disorder (ASD) and ileocolitis. PLoS One. 2013;8(3):e58058.
Deth RC, Hodgson NW, Walker S, Krigsman A, Trivedi MS. Role of the GI tract in neuroepigenetic regulation during early development and its implications for autism In: Arranga T, Viadro C, Underwood L, Herbert MR, eds. Bugs, bowels, and behavior: the groundbreaking story of the gut-brain connection. New York: Skyhorse Publishing;2013: 187-195.
Moorefield EC, McKee EE, Solchaga L, Orlando G, Yoo JJ, Walker S, Furth ME, Bishop CE. Cloned, CD117 selected human amniotic fluid stem cells are capable of modulating the immune response. PLoS ONE. 2011;6(10):e26535.
Markert CD, Meaney MP, Voelker KA, Grange RW, Dalley HW, Cann JK, Ahmed M, Bishwokarma B, Walker SJ, Childers MK, et al. Functional muscle analysis of the Tcap knockout mouse. Hum Mol Genet. 2010;19(11):2268-2283.
Fan X, Lobenhofer EK, Chen M, Shi W, Huang J, Luo J, Zhang J, Walker SJ, Chu TM, Li L, et al. Consistency of predictive signature genes and classifiers generated using different microarray platforms. Pharmacogenomics J. 2010;10(4):247-257.
Shi L, Campbell G, Jones WD, Campagne F, Wen Z, Walker SJ, Su Z, Chu T-M, Goodsaid FM, Pusztai L, et al. The MicroArray Quality Control (MAQC)-II study of common practices for the development and validation of microarray-based predictive models. Nat Biotechnol. 2010;28(8):827-838.
Chung Y, Bishop CE, Treff NR, Walker SJ, Sandler VM, Becker S, Klimanskaya I, Wun W-S, Atala A, Lanza R, et al. Reprogramming of human somatic cells using human and animal oocytes. Cloning Stem Cells. 2009;11(2):213-223.
Walker SJ, Segal J, Aschner M. Cultured lymphocytes from autistic children and non-autistic siblings up-regulate heat shock protein RNA in response to thimerosal challenge. Neurotoxicology. 2006;27(5):685-692.
Patterson TA, Lobenhofer EK, Fulmer-Smentek SB, Collins PJ, Chu T-M, Bao W, Fang H, Kawasaki ES, Hager J, Walker SJ, et al. Performance comparison of one-color and two-color platforms within the MicroArray Quality Control (MAQC) project. Nat Biotechnol. 2006;24(9):1140-1150.
Shi LM, Reid LH, Jones WD, Shippy R, Warrington JA, Baker SC, Collins PJ, de Longueville F, Kawasaki ES, Walker SJ, et al. The MicroArray Quality Control (MAQC) project shows inter- and intraplatform reproducibility of gene expression measurements. Nat Biotechnol. 2006;24(9):1151-1161.
Ferguson B, Grant KA, Walker SJ. Alpha-synuclein polymorphism and mRNA levels associated with ethanol self-adminsitration [sic] in monkeys [abstract]. Alcohol Clin Exp Res. 2006;30(6 Suppl):120A.
Walker SJ, Sutter TR, Grant KA. Effects of ethanol self-administration on peripheral blood gene expression in monkeys [abstract]. Alcohol Clin Exp Res. 2006;30(6 Suppl):180A.
Graves JT, Walker SJ. Microarray analysis of TNFRSF and other cytokine mRNAS differentially regulated in autistic, EBV-immortalized B-lymphocytes [abstract]. Neurotoxicology. 2006;27(6):1184.
Walker SJ, Nelson A, Blaxill M, Aschner M. Transport of ethylmercury and methylmercury in an in vitro blood-brain barrier model [abstract]. Neurotoxicology. 2006;27(6):1185.
Dr. Walker received his doctorate in Genetics & Developmental Biology at West Virginia University followed by post-graduate work at Wake Forest University Health Sciences in the areas of molecular biology and proteomics. His initial faculty appointment was in the Department of Pediatrics, Section on Medical Genetics, at Wake Forest University Health Sciences. In this position he recruited families and carried out genetic association studies related to single-gene craniofacial disorders. From there he moved to the faculty in theDepartment of Physiology & Pharmacology where he participated in studies examining the molecular basis for substance abuse using nonhuman primate animal models. It is in this position that he was first introduced to microarray technology (looking at gene expression at the “whole transcriptome” level). Dr. Walker has been a member of the FDA-sponsored International Microarray Quality Control (MAQC) consortium since its inception in 2005. He is currently on the faculty at the Wake Forest Institute for Regenerative Medicine and is also on the Graduate faculty as well as faculty in the Neuroscience Program.
SYNOPSIS OF AREA OF INTERESTDr. Walker is broadly interested in using and developing molecular tools, especially array-based and sequencing technologies, to better understand transcriptional control that underlies development and disease processes.