Brain chemistry changes in children with autism offer clues to earlier detection and intervention

Between ages three and 10, children with autism spectrum disorder exhibit distinct brain chemical changes that differ from children with developmental delays and those with typical development, according to a new study led by University of Washington researchers.

The finding that early brain chemical alterations tend to normalize during the course of development in children with ASD gives new insight to efforts to improve early detection and intervention. The findings were reported July 31 in the Journal of the American Medical Assocation Psychiatry.

“In autism, we found a pattern of early chemical alterations at the cellular level that over time resolved – a pattern similar to what others have seen with people who have had a closed head injury and then got better,” said Stephen R. Dager, a UW professor of radiology and adjunct professor of bioengineering and associate director of UW’s Center on Human Development and Disability.

Neva Corrigan, a senior research fellow in radiology, was first author and Dager corresponding author of the study, titled “Atypical Developmental Patterns of Brain Chemistry in Children with Autism Spectrum Disorder.”

“The brain developmental abnormalities we observed in the children with autism are dynamic, not static. These early chemical alterations may hold clues as to specific processes at play in the disorder and, even more exciting, these changes may hold clues to reversing these processes,” Dager said.

In the study, scientists compared brain chemistry among three groups of children: those with a diagnosis of ASD, those with a diagnosis of developmental delay, and those considered typically developing. The researchers used magnetic resonance spectroscopic imaging, a type of MRI, to measure tissue-based chemicals in three age groups: 3-4 years, 6-7 years and 9-10 years.

One of the chemicals measured, N-acetylaspartate (NAA), is thought to play an important role in regulating synaptic connections and myelination. Its levels are decreased in people with conditions such as Alzheimer’s, traumatic brain injury or stroke. Other chemicals examined in the study – choline, creatine, glutamine/glutamate and myo-inositol – help characterize brain tissue integrity and bioenergetic status.

A notable finding concerned changes in gray matter NAA concentration: In scans of the 3- to 4-year-olds, NAA concentrations were low in both the ASD and developmentally delayed groups. By 9 to 10 years, NAA levels in the children with ASD had caught up to the levels of the typically developing group, while low levels of NAA persisted in the developmentally delayed group.

“A substantial number of kids with early, severe autism symptoms make tremendous improvements. We’re only measuring part of the iceberg, but this is a glimmer that we might be able to find a more specific period of vulnerability that we can measure and learn how to do something more proactively,” said Annette Estes, a co-author of the study and director of the UW Autism Center. She is an associate professor of speech and hearing sciences.

Study co-author Dennis Shaw, a UW professor of radiology and director of MRI at Seattle Children’s, observed that the findings “parallel some of the early brain structural differences we and others have found on MRI that also appear to normalize over time in children with autism. These chemical findings will help to better establish the timing and mechanisms underlying genetic abnormalities known to be involved in at least some cases of autism.”

Dager and UW colleagues are currently using more advanced MRI methods to study infants at risk for ASD because of an older sibling with autism.

“We’re looking prospectively at these children starting at 6 months to determine if we can detect very early alterations in brain cell signaling or related cellular disruption that may precede early, subtle clinical symptoms of ASD.”

Despite the encouraging finding, science has yet to pinpoint the when, what and why of autism’s inception, an event often likened to the flipping of a switch. Discovering the earliest period that a child’s brain starts to develop a profile of ASD is crucial because, as the study acknowledged, “even a relatively brief period of abnormal signaling between glial cells and neurons during early development would likely have a lasting effect” on how a child’s brain network develops.

This study also suggests that developmental delay and autism spectrum disorder are distinct disorders having different underlying brain mechanisms and treatment considerations, Dager said.

“Autism appears to have a different pathophysiology and different early biological course than idiopathic developmental disorder. There are differences in their underlying biological processes; this supports the notion that ASD is different from developmental delay and challenges the notion that the increasing prevalence of autism merely reflects a re-categorization of symptoms between autism and intellectual disabilities.”

Stray prenatal gene network suspected in schizophrenia

Researchers have reverse-engineered the outlines of a disrupted prenatal gene network in schizophrenia, by tracing spontaneous mutations to where and when they likely cause damage in the brain. Some people with the brain disorder may suffer from impaired birth of new neurons, or neurogenesis, in the front of their brain during prenatal development, suggests the study, which was funded by the National Institutes of Health.

“Processes critical for the brain’s development can be revealed by the mutations that disrupt them,” explained Mary-Claire King, Ph.D., University of Washington (UW), Seattle, a grantee of NIH’s National Institute of Mental Health (NIMH). “Mutations can lead to loss of integrity of a whole pathway, not just of a single gene. Our results implicate networked genes underlying a pathway responsible for orchestrating neurogenesis in the prefrontal cortex in schizophrenia.”

King, and collaborators at UW and seven other research centers participating in the NIMH genetics repository, report on their discovery Aug. 1, 2013 in the journal Cell.

“By linking genomic findings to functional measures, this approach gives us additional insight into how early development differs in the brain of someone who will eventually manifest the symptoms of psychosis,” said NIMH Director Thomas R. Insel, M.D.

Earlier studies had linked spontaneous mutations to non-familial schizophrenia and traced them broadly to genes involved in brain development, but little was known about convergent effects on pathways. King and colleagues set out to explore causes of schizophrenia by integrating genomic data with newly available online transcriptome resources that show where in the brain and when in development genes turn on. They compared spontaneous mutations in 105 people with schizophrenia with those in 84 unaffected siblings, in families without previous histories of the illness.

Unlike most other genes, expression levels of many of the 50 mutation-containing genes that form the suspected network were highest early in fetal development, tapered off by childhood, but conspicuously increased again in early adulthood – just when schizophrenia symptoms typically first develop. This adds to evidence supporting the prevailing neurodevelopmental model of schizophrenia. The implicated genes play important roles in migration of cells in the developing brain, communication between brain cells, regulation of gene expression, and related intracellular workings.

Having an older father increased the likelihood of spontaneous mutations for both affected and unaffected siblings. Yet affected siblings were modestly more likely to have mutations predicted to damage protein function. Such damaging mutations were estimated to account for 21 percent of schizophrenia cases in the study sample. The mutations tend to be individually rare; only one gene harboring damaging mutations turned up in more than one of the cases, and several patients had damaging mutations in more than one gene.

The networks formed by genes harboring these damaging mutations were found to vary in connectivity, based on the extent to which their proteins are co-expressed and interact. The network formed by genes harboring damaging mutations in schizophrenia had significantly more nodes, or points of connection, than networks modeled from unaffected siblings. By contrast, the network of genes harboring non-damaging mutations in affected siblings had no more nodes than similar networks in unaffected siblings.

When the researchers compared such network connectivity across different brain tissues and different periods of development, they discovered a notable difference between affected and unaffected siblings: Genes harboring damaging mutations that are expressed together in the fetal prefrontal cortex of people with schizophrenia formed a network with significantly greater connectivity than networks modeled from genes harboring similar mutations in their unaffected siblings at that time in development.

The study results are consistent with several lines of evidence implicating the prefrontal cortex in schizophrenia. The prefrontal cortex organizes information from other brain regions to coordinate executive functions like thinking, planning, attention span, working memory, problem-solving, and self-regulation. The findings suggest that impairments in such functions — often beginning before the onset of symptoms in early adulthood, when the prefrontal cortex fully matures – appear to be early signs of the illness.

The study demonstrates how integrating genomic data and transcriptome analysis can help to pinpoint disease mechanisms and identify potential treatment targets. For example, the mutant genes in the patients studied suggest the possible efficacy of medications targeting glutamate and calcium channel pathways, say the researchers.

"These results are striking, as they show that the genetic architecture of schizophrenia cannot be understood without an appreciation of how genes work in temporal and spatial networks during neurodevelopment," said Thomas Lehner, Ph.D., chief of the NIMH Genomics Research Branch.

Re-learning how to see: researchers find crucial on-off switch in visual development

A new discovery by a University of Maryland-led research team offers hope for treating “lazy eye” and other serious visual problems that are usually permanent unless they are corrected in early childhood.

Amblyopia afflicts about three percent of the population, and is a widespread cause of vision loss in children. It occurs when both eyes are structurally normal, but mismatched – either misaligned, or differently focused, or unequally receptive to visual stimuli because of an obstruction such as a cataract in one eye.

During the so-called “critical period” when a young child’s brain is adapting very quickly to new experiences, the brain builds a powerful neural network connecting the stronger eye to the visual cortex. But the weaker eye gets less stimulation and develops fewer synapses, or points of connection between neurons. Over time the brain learns to ignore the weaker eye. Mild forms of amblyopia such as “lazy eye” result in problems with depth perception. In the most severe form, deprivation amblyopia, a cataract blocks light and starves the eye of visual experiences, significantly altering synaptic development and seriously impairing vision.

Because brain plasticity declines rapidly with age, early diagnosis and treatment of amblyopia is vital, said neuroscientist Elizabeth M. Quinlan, an associate professor of biology at UMD. If the underlying cause of amblyopia is resolved early enough, the child’s vision can recover to normal levels. But if the treatment comes after the end of the critical period and the loss of synaptic plasticity, the brain cannot relearn to see with the weaker eye.

“If a child is born with a cataract and it is not removed very early in life, very little can be done to improve vision,” Quinlan said. “The severe amblyopia that results is the most difficult to treat. For that reason, science has the most to gain by a better understanding of the underlying mechanisms.”

Quinlan, who specializes in studying how communication through the brain’s circuits changes over the course of a lifetime, wanted to find out what process controls the timing of the critical period of synaptic plasticity. If researchers could find the neurological on-off switch for the critical period, she reasoned, clinicians could use the information to successfully treat older children and adults.

Researchers in Quinlan’s University of Maryland lab teamed up with the laboratory of Alfredo Kirkwood at Johns Hopkins University to address two questions: What are the age boundaries of the critical period for synaptic plasticity, when it comes to determining eye dominance? And what developmental processes are involved?

Experiments in rodents suggested the timing of the critical period is controlled by a specific class of inhibitory neurons, which come into play after a visual stimulus activates excitatory neurons that link the eye to the visual cortex. The inhibitory neurons act as signal controllers, affecting the interactions between excitatory neurons and synapses.

“The generally accepted view has been that as the inhibitory neurons develop, synaptic plasticity declines, which was thought to occur at about five weeks of age in rodents,” roughly equivalent to five years of age in humans, Quinlan said. But in earlier experiments, Quinlan and Kirkwood found no correlation between the development of these inhibitory neurons and the loss of plasticity. In fact, they found the visual circuitry in rodents was highly adaptable at ages beyond five weeks.

In their latest research the UMD-led team looked “one synapse upstream from these inhibitory neurons,” Quinlan said, studying the control of that synapse by a protein called NARP (Neuronal Activity-Regulated Pentraxin). Working with two sets of mice – one group genetically similar to wild mice and another that lacked the NARP gene - the researchers covered one eye in each animal to simulate conditions that produce amblyopia.

The mice that were genetically similar to wild mice developed amblyopia, with characteristic dominance of the normal eye over the deprived eye. But the mice that lacked NARP did not develop amblyopia, regardless of age or the length of time one eye was deprived of stimulation.

The study, published in the current issue of the peer-reviewed journal Neuron, demonstrated that only one specific class of synapses was affected by the absence of NARP. Without NARP, the mice simply had no critical period in which the brain circuitry was weakened in response to the impaired blocking vision in one eye, Quinlan said. Except for the lack of this plasticity, their vision was normal.

“It’s remarkable how specific the deficit is,” Quinlan said. Without the NARP protein, “these animals develop normal vision. Their brain circuitry just isn’t plastic. We can completely turn off the critical period for plasticity by knocking out this protein.”

Since there are indications that NARP levels vary with age, the discovery raises hope that a treatment targeting NARP levels in humans could allow correction of amblyopia late in life, without affecting other aspects of vision.

FASD impacts brain development throughout childhood and adolescence not just at birth

Medical researchers at the University of Alberta recently published findings showing that brain development is delayed throughout childhood and adolescence for people born with Fetal Alcohol Spectrum Disorder (FASD).

Christian Beaulieu and Carmen Rasmussen, the two primary investigators in the research study, recently published the results of their work in the peer-reviewed journal, The Journal of Neuroscience. Their team scanned 17 people with FASD, and 27 people without the disorder, who were between 5 and 15 years old. Each participant underwent two to three scans, with each scan taking place two to four years apart. This is the first research study involving multiple scans of the same FASD study participants.

Researchers used an advanced MRI method that examines white matter in the brain. White matter forms connections between various regions of the brain and usually develops significantly during childhood and adolescence. Those who took part in the study were imaged multiple times, to see what kinds of changes occurred in brain development as the participants aged. Those without the disorder had marked increases in brain volume and white matter – growth that was lacking in those with FASD. However, the advanced MRI method revealed greater changes in the brain wiring of white matter in the FASD group, which the authors suggest may reflect compensation for delays in development earlier in childhood.

“These findings may suggest that significant brain changes happened earlier in the study participants who didn’t have FASD,” says the study’s first author, Sarah Treit, who is a student in the Centre for Neuroscience at the U of A. “This study suggests alcohol-induced injury with FASD isn’t static – those with FASD have altered brain development, they aren’t developing at the same rate as those without the disorder. And our research showed those with FASD consistently scored lower on all cognitive measures in the study.”

Treit said the research team also made other important observations. Children with FASD who demonstrated the greatest changes in white matter development also made the greatest gains in reading ability – “so the connection seems relevant.” And those with the most severe FASD showed the greatest changes in white matter brain wiring. Scans also confirmed those with FASD have less overall brain volume – this issue neither rectified itself nor worsened throughout the course of the study.

Beaulieu is a researcher in the Department of Biomedical Engineering, while Rasmussen works in the Department of Pediatrics. Their research was funded by the Canadian Institutes of Health Research.

The team is continuing their research in this area, in hopes of finding a biomarker for FASD, and to examine how the brain changes from adolescence into adulthood in those with the disorder. The advanced MRI imaging the team used can pinpoint brain damage present in those with FASD, and could one day guide medical interventions for those with the disorder, which affects one in every 100 Canadians.

Robots Strike Fear in the Hearts of Fish

Anxious Zebrafish Help NYU-Poly Researchers Understand How Alcohol Affects Fear

The latest in a series of experiments testing the ability of robots to influence live animals shows that bio-inspired robots can not only elicit fear in zebrafish, but that this reaction can be modulated by alcohol. These findings may pave the way for new methodologies for understanding anxiety and other emotions, as well as substances that alter them.

Maurizio Porfiri, associate professor of mechanical and aerospace engineering at the Polytechnic Institute of New York University (NYU-Poly) and Simone Macrì, a collaborator at the Istituto Superiore di Sanità in Rome, Italy, published their findings in PLOS ONE, an international, peer-reviewed, open-access, online publication.

This latest study expands Porfiri and Macrì’s efforts to determine how bio-inspired robots can be employed as reliable stimuli to elicit reactions from live zebrafish. Previous studies have established that zebrafish show a strong affinity for robotic members designed to swim and appear as one of their own and that this preference can be abolished by exposing the fish to ethanol.

Porfiri and Macri, along with students Valentina Cianca and Tiziana Bartolini, hypothesized that robots could be used to induce fear as well as affinity and designed a robot mimicking the morphology and locomotion pattern of the Indian leaf fish, a natural predator of the zebrafish. In the lab, they simulated a harmless predatory scenario, placing the zebrafish and the robotic Indian leaf fish in separate compartments of a three-section tank. The other compartment was left empty. The control group uniformly avoided the robotic predator, showing a preference for the empty section.

To determine whether alcohol would affect fear responses, the researchers exposed separate groups of fish to different doses of ethanol in water. Ethanol has been shown to influence anxiety-related responses in humans, rodents and some species of fish. The zebrafish exposed to the highest concentrations of ethanol showed remarkable changes in behavior, failing to avoid the predatory robot. Acute administration of ethanol causes no harm and has no lasting effect on zebrafish.

“These results are further evidence that robots may represent an exciting new approach in evaluating and understanding emotional responses and behavior,” said Porfiri. “Robots are ideal replacements as independent variables in tests involving social stimuli—they are fully controllable, stimuli can be reproduced precisely each time, and robots can never be influenced by the behavior of the test subjects.”

To validate their findings and ensure that the zebrafish behavior being modulated was, in fact, a fear-based response, Porfiri and his collaborators conducted two traditional anxiety tests and evaluated whether the results obtained therein were sensitive to ethanol administration.

They placed test subjects in a two-chamber tank with one well-lit side and one darkened side, to establish which conditions were preferable. In a separate tank, they simulated a heron attack from the water’s surface—herons also prey on zebrafish—and measured how quickly and how many fish took shelter from the attack. As expected, the fish strongly avoided the dark compartment, and most sought shelter very quickly from the heron attack. Ethanol exposure significantly modulated these fear responses as well, abolishing the preference for the light compartment and significantly slowing the fishes’ retreat to shelter during the simulated attack.

“We hoped to see a correlation between the robotic Indian leaf fish test results and the results of the other anxiety tests, and the data support that,” Porfiri explained. “The majority of control group fish avoided the robotic predator, preferred the light compartment and sought shelter quickly after the heron attack. Among ethanol-exposed fish, there were many more who were unaffected by the robotic predator, preferred the dark compartment and were slow to swim to shelter when attacked.”

Porfiri and his colleagues believe zebrafish may be a suitable replacement for higher-order animals in tests to evaluate emotional responses. This novel robotic approach would also reduce the number of live test subjects needed for experiments and may inform other areas of inquiry, from collective behavior to animal protection.

Scientists decode mechanisms of cell orientation in the brain

Transmembrane protein NG2 controls orientation of cell migration toward the wound / Publication in the prestigious Journal of Neuroscience

When the central nervous system is injured, oligodendrocyte precursor cells (OPC) migrate to the lesion and synthesize new myelin sheaths on demyelinated axons. Scientists at the Institute of Molecular Cell Biology at Johannes Gutenberg University Mainz (JGU) have now discovered that a distinct protein regulates the direction and movement of OPC toward the wound. The transmembrane protein NG2, which is expressed at the surface of OPCs and down-regulated as they mature to myelinating oligodendrocytes, plays an important role in the reaction of OPC to wounding. The results of this study have recently been published in the renowned Journal of Neuroscience.

The myelin sheath functions to electrically isolate axons of many nerve fibers and is synthesized by oligodendrocytes which mature from the OPC. In the case of injury, neural cells send out signaling molecules which attract the OPC. The NG2 protein helps OPCs to react to some of these and move in a directed and orientated fashion. “We were able to prove in cell biological experiments that NG2 orientates OPC toward the lesion and ensures targeted OPC migration toward the wound through the regulation of cell polarity”, explained Dr. Fabien Binamé, lead author of the study. Supported by funding of the German Research Foundation (DFG), Dr. Fabien Binamé is currently carrying out his research at the Institute of Molecular Cell Biology headed by Professor Jacqueline Trotter.

"The function and mode of operation of NG2 is not yet fully understood", added co-author Dominik Sakry, who was also involved in the study. "But it looks as if the NG2-associated regulatory mechanism becomes apparent only in cases of injury of the nervous system."

Diseases such as Multiple Sclerosis or brain tumors go hand in hand with damage of nerve tissue. “The results of our study on NG2-mediated basic mechanisms of cell orientation and migration could aid in understanding the repair of damaged demyelinated tissue, or be important for treatment of highly active migratory brain tumors which often express high levels of NG2”, said Professor Jacqueline Trotter, head of the JGU Institute of Molecular Cell Biology.