Environmental Factor, January 2011, National Institute of Environmental Health Sciences
Guest lecture underscores environmental links to autism
By Thaddeus Schug
Hertz-Picciotto called for more research into the environmental causes of autism. In addition to the CHARGE Study, she and colleagues at UCD are participating in the NIEHS-sponsored Early Autism Risk Longitudinal Investigation (EARLI) and the Markers for Autism Risk in Babies - Learning Early Signs (MARBLES) programs. (Photo courtesy of Steve McCaw)
Shown, left to right, NIEHS intramural program scientists Stephanie London, M.D., Dr.P.H., Matthew Longnecker, M.D., Sc.D., and Windy Boyd, Ph.D., listened attentively during the seminar. (Photo courtesy of Steve McCaw)
NIEHS toxicologist Jean Harry, Ph.D., whose research involves toxic exposure to the brain and nervous system, questioned Hertz-Picciotto about her studies involving mercury exposure and autism risks. (Photo courtesy of Steve McCaw)
Lecture host Cindy Lawler, Ph.D., left, and colleague Kim Gray, Ph.D., have both overseen grants supporting Hertz-Picciotto's research. (Photo courtesy of Steve McCaw)
Environmental factors are likely among several contributors to the rapid rise in new cases of autism seen in California and throughout the nation, according to guest lecturer Irva Hertz-Picciotto, Ph.D., an epidemiologist and NIEHS grantee (http://tools.niehs.nih.gov/portfolio/index.cfm?action=portfolio.grantdetail&grant_number=R01ES015359) at the University of California (UC), Davis.
Hertz-Picciotto (http://www.ucdmc.ucdavis.edu/search/faculty/biodetail.asp?bioid=855) reported these findings Dec. 6 in a seminar titled, "An Update on Environment and Autism: Findings from the CHARGE [Childhood Autism Risks from Genetics and Environment] Study," as part of the Keystone Science Lecture Seminar Series at NIEHS. Hertz-Picciotto is chief of the division of environmental and occupational health at UC Davis, and principal investigator of the NIEHS-funded study.
The combination of changes in diagnostic criteria, increased parental awareness, and environmental risk factors, has led to an eight-fold increase in cases of autism in the past ten years, she explained.
Gene and environment interaction
The NIEHS-funded CHARGE Study began in 2003 as one of the projects in the UC Davis Center for Children's Environmental Health and Disease Prevention. The study has examined 1,400 children with differing patterns of development. The goal of the program is to better understand the causes and contributing factors for autism or developmental delay.
Three groups of children are currently enrolled in the CHARGE study: children with autism, children with developmental delay who do not have autism, and children from the general population. All of them are evaluated for a broad array of exposures and genetic susceptibilities.
Many researchers believe the continuous increase in autism cases over the last decade can be explained solely by artifacts, such as the recent broadening of the diagnostic criteria. "These artifacts do explain part of the rise in autism cases, but they don't account for the majority of the trends we are witnessing," said Hertz-Picciotto.
Hertz-Picciotto explained that evidence gathered from studies of monozygotic (identical) twins and the rubella epidemic in the late 1960's revealed that congenital exposure is associated with incidence rates of autism. "Environmental factors are not limited to just chemical exposure. We need to account for the physical, social, and developmental world of children," added Hertz-Picciotto.
The complexities of autism
"It is becoming more and more evident that multiple environmental and genetic factors contribute to elevated risks of autism, and the challenge is identifying these associations," said Hertz-Picciotto. "I don't believe that just one gene or one exposure can account for all cases of autism - it is much more complicated than that," she noted (see related story (http://www.niehs.nih.gov/news/newsletter/2011/january/science-mitochondrial.cfm)).
"The CHARGE study was designed to cast a very broad net to try to capture potential gene-environmental factors associated with the risks of autism," said Hertz-Picciotto. She pointed to a case in which her group examined the autism rates associated with maternal supplementation and genes associated with one carbon metabolism. "What we found was that children with certain genetic polymorphisms, born to mothers who supplemented their diet with folic acid, had much lower incidences of autism."
Hertz-Picciotto concluded the seminar saying, "A lot has changed in the environment over the last 10 to 15 years, especially our exposure to chemicals in our food and in our homes." She pointed out that dozens of chemicals in the environment are neurodevelopmental toxins, which means they alter how the brain grows. "Mercury, polychlorinated biphenyls, lead, brominated flame retardants, and pesticides are just a few potential culprits that we need to study in more detail," she added.
"Irva's work illustrates the enormous complexities and challenges found in autism research," said Cindy Lawler, Ph.D., a program administrator in the NIEHS Division of Extramural Research and Training, and organizer of the lecture. Lawler added, "Clearly, more and more evidence is emerging that implicates the role of gene-environment interactions in the etiology of autism."
(Thaddeus Schug, Ph.D., is a postdoctoral research fellow in the NIEHS Laboratory of Signal Transduction and a regular contributor to the Environmental Factor. He is currently on detail as a program analyst in the NIEHS Division of Extramural Research and Training.)