Navigation Links
Research shows how PCBs promote dendrite growth, may increase autism risk
Date:4/25/2012

(SACRAMENTO, Calif.) New research from UC Davis and Washington State University shows that PCBs, or polychlorinated biphenyls, launch a cellular chain of events that leads to an overabundance of dendrites the filament-like projections that conduct electrochemical signals between neurons and disrupts normal patterns of neuronal connections in the brain.

"Dendrite growth and branching during early development is a finely orchestrated process, and the presence of certain PCBs confuses the conductor of that process," said Pamela Lein, a developmental neurobiologist and professor of molecular biosciences in the UC Davis School of Veterinary Medicine. "Impaired neuronal connectivity is a common feature of a number of conditions, including autism spectrum disorders."

Reported today in two related studies in the journal Environmental Health Perspectives, the findings underscore the developing brain's vulnerability to environmental exposures and demonstrate how PCBs could add to autism risk.

"We don't think PCB exposure causes autism," Lein said, "but it may increase the likelihood of autism in children whose genetic makeup already compromises the processes by which neurons form connections."

The senior authors of the studies were Lein and Isaac Pessah, chair of molecular biosciences in the School of Veterinary Medicine and director of the Center for Children's Environmental Health at UC Davis. Both are researchers with the UC Davis MIND Institute, which is dedicated to finding answers to autism and other neurodevelopmental disorders. The lead author was Gary Wayman of Washington State University's Program in Neuroscience, who first described the molecular pathway that controls the calcium signaling in the brain that guides normal dendrite growth.

Wayman found that key cellular players, called calcium and calmodulin kinases, are activated by increased calcium levels. Activated calmodulin kinase then turns on the protein known as CREB that regulates genes that produce Wnt2, a potent molecule and the final arbiter of whether and how dendrites grow. Wnt2 directs structural proteins to construct scaffolding that supports dendrite growth and branching.

"Orderly choreography of the calmodulin kinase-to-Wnt2 pathway translates normal increases in calcium levels into normal levels of dendrite production," said Wayman. "The wiring of billions of neurons is dependent on the health of this cellular process and is crucial to proper development of virtually all complex behaviors, learning, memories and language."

For the current studies, the team set out to determine if that pathway was altered by exposure to PCBs, focusing on neurons of the hippocampus the brain region linked with learning and memory and known to suffer impaired connectivity in many neurodevelopmental disorders.

The scientists also focused on the effects of an understudied PCB subset known as non-dioxin-like PCBs, which have been shown to increase calcium levels in neurons. Both non-dioxin-like PCBs and the more familiar dioxin-like subset were widely used in electrical equipment in the 1950s and 1960s. Banned in the 1970s because of the potential for dioxin-like PCBs to cause cancer, all PCBs are stable compounds that persist throughout the environment today.

One of the current UC Davis studies examined dendrite growth in rat pups born to and nursed by PCB-exposed mothers. Another study analyzed how PCBs affect rat neurons in cell cultures at developmental stages similar to those in the third trimester of pregnancy in humans. In both studies, PCB exposure levels were similar to those found in the human diet and in human tissues, including the placenta and breast milk.

Evaluation of the brains of the rats exposed to PCBs early in life showed significant overproduction of dendrites. The cellular studies showed that PCBs triggered the calcium pathway that led to the aberrant brain architecture, and that dendrite production was normal when that cellular pathway was blocked.

"We are the first to show that non-dioxin-like PCBs alter how the developing brain gets wired by hijacking the calcium signaling pathway and greatly expanding dendrite growth," said Lein.

The experiments also helped identify for the first time the specific trigger for this cellular chain of events as the ryanodine receptor (RyR) calcium channel. Pessah, a recognized leader in calcium-channel dysfunction and neurodevelopment, previously showed that RyR is selectively activated by non-dioxin-like PCBs. The new studies prove that RyR is a necessary component in the pathway that controls dendritic growth.

"These same calcium pathways are implicated in some forms of autism and, while environmental exposures alone do not cause autism, these new findings provide good evidence that PCBs could add to autism risk in genetically predisposed children," said Pessah. "Understanding the fundamental mechanisms by which PCBs alter neural networks sets the stage for research on environmental contaminants that are structurally related to PCBs, including flame retardants, and their risks to susceptible populations."


'/>"/>
Contact: Karen Finney
karen.finney@ucdmc.ucdavis.edu
916-734-9064
University of California - Davis Health System
Source:Eurekalert

Related biology news :

1. Researchers announce GenomeSpace environment to connect genomic tools
2. BGI and Aspera collaborate on high-speed data exchange to advance genome research
3. Evidence shows that anti-depressants likely do more harm than good, researchers find
4. Scientists advance field of research with publication of newly validated method for analyzing flavanols in cocoa
5. Scripps research scientists find anticonvulsant drug helps marijuana smokers kick the habit
6. Johns Hopkins researchers uncover genes at fault for cystic fibrosis-related intestinal obstruction
7. Researchers find mechanism that gives plants balance
8. Research is ensuring stormwater systems are designed for the future
9. New research underscores the health benefits of fibers, including bone health
10. Research on carbon-consuming life-forms in Antarctica published in JoVE
11. Climate change may create price volatility in the corn market, say Stanford and Purdue researchers
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:6/22/2016)... , June 22, 2016  The American College of Medical ... Show Executive Magazine as one of the fastest-growing trade ... 25-27 at the Bellagio in Las Vegas ... highest percentage of growth in each of the following categories: ... companies and number of attendees. The 2015 ACMG Annual Meeting ...
(Date:6/20/2016)... Securus Technologies, a leading provider of ... safety, investigation, corrections and monitoring announced that after ... secured the final acceptance by all three (3) ... Systems (MAS) installed. Furthermore, Securus will have contracts ... by October, 2016. MAS distinguishes between legitimate wireless ...
(Date:6/9/2016)... , June 9, 2016 ... Police deploy Teleste,s video security solution to ensure the safety ... France during the major tournament Teleste, ... communications systems and services, announced today that its video security ... to back up public safety across the country. ...
Breaking Biology News(10 mins):
(Date:6/23/2016)... Md. , June 23, 2016 A person ... from the crime scene to track the criminal down. ... the U.S. Food and Drug Administration (FDA) uses DNA evidence ... Sound far-fetched? It,s not. The FDA ... sequencing to support investigations of foodborne illnesses. Put as simply ...
(Date:6/23/2016)... , June, 23, 2016  The Biodesign Challenge ... envision new ways to harness living systems and biotechnology, ... Art (MoMA) in New York City ... 130 participating students, showcased projects at MoMA,s Celeste Bartos ... Paola Antonelli , MoMA,s senior curator of architecture and ...
(Date:6/23/2016)... ... , ... In a new case report published today in STEM CELLS Translational ... lymphedema after being treated for breast cancer benefitted from an injection of stem cells ... this debilitating, frequent side effect of cancer treatment. , Lymphedema refers to ...
(Date:6/23/2016)... NEW YORK , June 23, 2016 ... the trading session at 4,833.32, down 0.22%; the Dow Jones ... the S&P 500 closed at 2,085.45, down 0.17%. Stock-Callers.com has ... INFI ), Nektar Therapeutics (NASDAQ: NKTR ... BIND Therapeutics Inc. (NASDAQ: BIND ). Learn more ...
Breaking Biology Technology: