Epigenetics is the change in gene expression controlled by environmental factors and scientists at the Albert Einstein College of Medicine of Yeshiva University have published their research in the PLOS Genetics journal suggesting that Autism Spectrum Disorder can result from environmental causes.
ASD is a hidden epidemic in the United States with rates as high as one in sixty eight children affected according to the latest estimates from the CDC (Center for Disease Control); a 30% increase in two years.
The researchers in this study focused on genetic as well as environmental influences in older mothers who have an increased risk of having children with ASD and analyzed the buccal epithelial cells of children that line the cheek. The study analyzed 47 children with ASD and 48 normally developing children of mothers who were 35 and older.
“We hypothesized that whatever influences lead to ASD in children of older women probably are already present in the reproductive cells that produce the embryo or during the very earliest stages of embryonic development — in cells that give rise to both the buccal epithelium and the brain,” said Dr. Greally, the study’s senior author and professor of genetics, of medicine and of pediatrics, director of the Center for Epigenomics. “This would mean that whatever abnormalities we found in the cheek cells of children with an ASD versus TD children should exist in their brain cells as well.”
The researchers examined the children’s cells for evidence of environmental effects in the form of methylated groups. “If environmental influences were exerted during embryonic development, they would encode a “memory” in cells that we can detect as chemical alterations of genes,” said Dr. Greally. “Most of these so-called epigenetic alterations are in the form of methyl groups that chemically bind to DNA. Such methyl groups are vital for controlling gene activity, but changes in methylation patterns can dysregulate cell function by altering gene expression or by silencing genes entirely.”
The study findings revealed that there two groups of genes that were epigenetically distinct in children with ASD compared with normal children. These genes have been associated with proteins expressed in the brain involved in nerve transmission functions previously shown to be impaired in ASD. The researchers may also have found a cause for the differentiation of ASD symptoms on the ASD spectrum as not all children possessed these two groups of distinctive genes, but were present in a subset of the ASD population examined. These genes interacted with genes known to be mutated in ASD individuals.
“Genes interact with each other to create molecular pathways that carry out important functions,” said Dr. Greally. “Our findings suggest that, at least in some individuals with an ASD, the same pathways in the brain seem to hit by both mutations and epigenetic changes. So the severity of someone’s ASD may depend on whether or not a gene mutation is accompanied by epigenetic alterations to related genes.”
The specific environmental factors related to causing these epigenetic effects in ASD individuals was not analyzed.
Esther R. Berko, Masako Suzuki, Faygel Beren, Christophe Lemetre, Christine M. Alaimo, R. Brent Calder, Karen Ballaban-Gil, Batya Gounder, Kaylee Kampf, Jill Kirschen, Shahina B. Maqbool, Zeineen Momin, David M. Reynolds, Natalie Russo, Lisa Shulman, Edyta Stasiek, Jessica Tozour, Maria Valicenti-McDermott, Shenglong Wang, Brett S. Abrahams, Joseph Hargitai, Dov Inbar, Zhengdong Zhang, Joseph D. Buxbaum, Sophie Molholm, John J. Foxe, Robert W. Marion, Adam Auton, John M. Greally. Mosaic Epigenetic Dysregulation of Ectodermal Cells in Autism Spectrum Disorder. PLoS Genetics, 2014; 10 (5): e1004402 DOI: 10.1371/journal.pgen.1004402