Eli Hatchwell, M.D., Ph.D., Associate Professor of Pathology at Stony Brook University Medical Center, and colleagues have found that a disruption of the Contactin 4 gene on chromosome 3 may be linked to autism spectrum disorder (ASD). What causes ASD, a developmental disorder of the central nervous system, is largely unknown. Dr. Hatchwell’s finding suggests that mutations affecting Contactin 4 may be relevant to ASD pathogenesis, and thus a potential biomarker for some individuals with the disorder.
According to the Centers for Disease Control and Prevention, the prevalence of ASD in the United States may be as high as 1 in 150 children. The disorder is divided into five subtypes, including autism proper. Pathogenesis of ASD may be environmental and/or biological. Experts suspect that many genes may play a role in the etiology of ASD.
“Given the prevalence of ASD, a clearer understanding of its etiology is necessary for both diagnostic and therapeutic purposes,” says Dr. Hatchwell, also Director of Stony Brook University’s Genomics Core Facility and Geneticist at the Cody Center for Autism and Developmental Disabilities at SBU. “Our study implicates Contactin 4 as a candidate gene in ASD, a finding that significantly contributes to our understanding of the biological basis of autism.”
A total of 92 patients with ASD from the Cody Center participated in the genetics study. The participants came from 81 families. Genomic DNA was analyzed from all subjects and, where relevant, from their biological parents. More than 500 normal control patients were included in the analysis.
A whole genome analysis of the 92 subjects revealed that three subjects had chromosome 3 copy number variations that disrupted the same gene, Contactin 4. A deletion was detected in two subjects (siblings), and a duplication was found in a third, unrelated, individual. Subsequent array analysis of parental DNA indicated that both variations were paternally inherited, specifically inherited from fathers without a history of ASD.
According to Dr. Hatchwell, when mutations are found that explain just one percent of a given ASD population, the results are significant, as ASD likely has a multitude of genetic causes. For example, a recent study reported in the New England Journal of Medicine showed that copy number variations of chromosome 16p11.2 accounted for one percent of all cases of the syndrome. Dr. Hatchwell explains that the genetic analysis with the Cody Center patients, detailed in the article entitled “Disruption of Contactin 4 in 3 Subjects with Autism Spectrum Disorder,” is highly significant in that two of 81 families (2.5 percent) presented with a disruption of Contactin 4.
The mutations found in Dr. Hatchwell’s study directly interrupt Contactin 4. The gene codes for an axon-associated cell adhesion molecule that is expressed in the brain and is known to be important in axonal development.
Dr. Hatchwell’s multidisciplinary research team is planning to analyze Contactin 4 in large numbers of patients with ASD and normal controls, in order to identify mutations that might be involved in the pathogenesis of ASD in a subset of affected individuals.
Details of the study are reported in the early online edition of the Journal of Medical Genetics. Dr. Hatchwell’s co-authors from Stony Brook University include: Jasmin Roohi, B.A., Department of Genetics; John C. Pomeroy, M.D., David H. Tegay, D.O., and Carla DeVincent, Ph.D., of the Department of Pediatrics; Lance E. Palmer, Ph.D., Department of Microbiology. Other authors include: Cristina Montagna, Ph.D., Department of Pathology and Molecular Genetics, Albert Einstein College of Medicine; Susan L. Christian, Ph.D., Department of Human Genetics, University of Chicago; and Norma Nowak, Ph.D., Department of Cancer Prevention and Population Sciences, University of Buffalo.
The study was supported in part by grants from the Cody Center for Autism and Developmental Disabilities, National Alliance for Autism Research, National Institute of Neurological Diseases and Stroke, the National Cancer Institute, and the General Clinical Research Center at SBUMC.
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