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News- Page 2
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Research : Autism research suggests genetic link
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Posted by sylvia on Saturday, March 25, 2006 (08:58:12)
RTE News
A team of researchers at Trinity College Dublin has identified several genes which may be linked to autism.
Dr Louise Gallagher, consultant and lecturer in child psychiatry at TCD, believes one of the genes may affect the ability of nerve cells in the brain to make connections.
Another is thought to influence an enzyme in the blood which could contribute to the severity of autism.
As part of a major international project, the team at the Smurfit Department of Genetics has been studying 200 Irish children with autism and their families.
New technology has allowed the researchers to examine the genetic make-up of the Irish families, scanning genes quickly and in much finer detail for over 10,000 variants.
Around 2,000 children and young adults have autism in Ireland, a condition whereby a person is unable to relate to people and situations.
Further findings from the TCD research are due to be published soon.
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Research : Autism 'extreme male brain' clue
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Posted by sylvia on Thursday, February 09, 2006 (09:05:42)
BBC online November 2005
The brain structure of people with autism is an "exaggeration" of the normal male brain, researchers suggest.
It has long been suggested that autistic behaviour is an exaggeration of male habits such as making lists.
But Cambridge Autism Research Centre researchers say the actual development of the autistic brain also exaggerates what happens in male brains.
Writing in Science, they say investigating this theory further will aid understanding of autism.
The team, led by Professor Simon Baron-Cohen, looked at research carried out into this "extreme male brain" explanation for autism.
They point to evidence that males generally have greater early growth of certain brain regions, and less hemispheric connectivity than females.
Ethical concerns
Boys' brains grow more quickly than girls'. In the brains of people with autism, this growth appears to occur to an even more extreme degree.
There are also specific differences seen in certain areas of the brain.
The amygdala, which plays a key role in emotional responses, is abnormally large in toddlers with autism; again an exaggeration of the typical development of the male brain.
The researchers say evidence points to exposure to male hormones, such as testosterone, before birth affecting these brain development patterns.
Male foetuses produce these hormones from their testes, and female foetuses from their adrenal glands.
So girls too could be exposed to higher than normal level of hormones.
Professor Baron-Cohen stressed researchers were interested in understanding autism.
"This is not about how we could intervene to prevent autism, or developing a pre-natal test.
"There are two ethical concerns; whether autism is a disease, which one would want to prevent or eradicate - a lot of people don't see it as a disease. These are simply children who develop differently.
"Secondly, there is the issue of pre-natal testing. Would a test be specific or sensitive enough?"
Eileen Hopkins, of the National Autistic Society, welcomed the Science paper: "Anything that adds to the body of knowledge on autism is clearly welcome," she said.
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Research : Main Autism Behaviour Types Are Not Genetically Linked
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Posted by sylvia on Wednesday, November 09, 2005 (11:10:58)
Medical News Today August 2005
Scientists at the MRC (Medical Research Council, UK) Social, Genetic and Developmental Psychiatry Centre at the Institute of Psychiatry, King's College London, have discovered that two sets of behaviours that co-occur in autism spectrum conditions appear to be caused by different sets of genes.
The report by Dr Angelica Ronald in collaboration with Professor Robert Plomin and Dr Francesca Happé - published in Developmental Science - could help advance future diagnosis, treatment and understanding of autism spectrum conditions.
In an autism diagnosis, two types of behaviours must be displayed; those that reflect social impairment such as a difficulty in making friends and non-social obsessive and repetitive behaviours such as sticking to rigid routines.
These two types of symptoms can both have massive impact on children's development. The researchers were motivated to investigate these two components separately because they represent two very different types of behaviours and it is not clear why they co-occur in autism spectrum conditions.
The study collected data from the UK-based Twins Early Development Study (TEDS) through parent and teacher reports on 3000 pairs of seven-year-old twins. Participants completed a questionnaire designed to assess social and non-social behaviours that are characteristic of autism spectrum conditions but also seen in the general population. The questions assessed the extent to which the twins displayed a range of behaviours, such as how considerate of other people's feelings they are or whether they are fussy and over-particular.
The researchers found that identical twins (where each twin shares the same set of genes) tended to show similar levels of social impairments to each other: i.e. both twins would show either many or few social impairments. In contrast, fraternal twins (where only a proportion of their genes are shared) often had very different levels of social impairments to each other. The same pattern of results was found in the twins for non-social behaviours. This demonstrated that both social and non-social behaviours are highly heritable, that is, a large proportion of the variation of these types of behaviours in the general population is due to genetic influences.
The researchers then posed themselves a new question: whether social and non-social behaviours are influenced by the same set of genes. If the same genes operate on both, one would expect high correlations between social impairments in one twin and non-social behaviours in the other twin in identical twin pairs. Lower correlations would be expected in fraternal twins because they do not share all their genes.
The researchers did not find evidence to suggest that the same genes are involved. They found that social and non-social impairments did not correlate very highly and in many cases, for example, if one identical twin showed social impairments, their co-twin did not show any non-social impairments. The results of this study indicated that most of the genes influencing social impairments are different to those that influence non-social behaviours.
Dr Angelica Ronald said: "This study suggests for the first time that social and non-social behaviours, which are both shown in autism spectrum conditions, are caused by mainly different sets of genes. It suggests that 'genes for autism' is a misnomer: there are several genetically distinct components involved. This finding has important implications for DNA and brain studies: it may be better to study the social and non-social components separately rather than requiring that a child has both components, which is what traditional diagnosis requires."
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Research : Genes play role in autism, researchers find
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Posted by sylvia on Tuesday, November 08, 2005 (20:54:12)
News Leader August 2005
By Sandy Kleffman
Providing one more clue for solving the autism mystery, researchers have discovered that the brain mechanism that stops or slows nerve impulses contributes to the disorder.
A team at Duke University Medical Center in Durham, N.C., found that genes that serve as "off switches" in the brain's neurons play a role. Exactly how such genes interact and what happens in the brains of autistic children remains unknown.
But the findings are sure to intrigue the many parents of autistic children who have long suspected their children suffer from a sensory overload.
The study will be published in the September issue of the American Journal of Human Genetics.
Autism remains one of the great mysteries of modern times. Once a rare disorder, it has drawn increased attention as the number of diagnosed cases jumped dramatically in recent years, sending scientists scrambling in search of a cause.
The latest study focused on gamma aminobutyric acid or GABA, a chemical that inhibits brain nerve cells from firing, thus telling the body to slow down. It acts as a sort of information filter, preventing the brain from becoming overstimulated.
"If it's not working or something's wrong with the GABA system, then you would think that there may be sensory overload," said Margaret Pericak-Vance, a lead researcher on the study and director of the Duke Center for Human Genetics. "This is what we think might be going on," she said. "Now what exactly is happening and how this is happening, we don't know that yet."
Most scientists believe there is a strong genetic component to autism. At least 10 genes and as many as 100 may be involved.
But thus far, researchers have been stymied in their attempt to find a single gene that plays a major role, Pericak-Vance said.
The latest study found that one GABA receptor gene interacting with a second GABA gene appeared to increase the risk of developing autism.
That led researchers to conclude that it may be a complex interaction of several genes that make children susceptible to the disorder.
"There's probably a minimum of 10 genes involved and it's going to be a challenge to try to decipher what they all are and the size of their effect," Pericak-Vance said.
"It's not a simple situation like some of the classic genetic diseases such as Huntington's disease or cystic fibrosis."
The study sheds no light on one of the most controversial issues surrounding autism: whether environmental factors trigger the disorder in genetically susceptible children. Parents have placed the blame on everything from mercury-containing vaccines to the numerous other chemicals young children are exposed to daily.
Others argue that better diagnosis and more awareness have caused the increase.
Pericak-Vance said the jury is still out.
The Duke University researchers examined 14 genes involved with the GABA receptor in 470 white families. They tested for associations between gene variations and the disease. They also used statistical methods to explore gene combinations.
The researchers hope their findings will lead to a method for determining children at highest risk of autism.
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Research : Complex gene interactions account for autism risk
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Posted by sylvia on Friday, September 30, 2005 (11:04:54)
MedicalNewsToday August 2005
Using a novel analysis of the interactions among related genes, Duke University Medical Center researchers have uncovered some of the first evidence that complex genetic interactions account for autism risk. The Duke team found that the brain mechanism that normally stops or slows nerve impulses contributes to the disease.
The team's findings implicate the so-called GABA receptor genes, which are genes that code for key components of "off switches" in the brain's neurons. GABA, or gamma aminobutyric acid, is a neurotransmitter - a chemical that one neuron fires at receptors on another neuron to trigger a response - in this case an inhibitory response. GABA receptors are protein switches nestled in nerve cell membranes that are triggered by GABA to cause such inhibition.
Importantly, the study found that the GABA brain system most likely exerts its influence via complex gene-gene interactions.
The current findings, and others that might result from the team's new approach, may ultimately point to methods for early diagnosis of autism, and perhaps new autism therapies, according to the researchers.
"Identifying the genes that contribute to cause autism has been challenging," said Margaret Pericak-Vance, Ph.D., director of the Duke Center for Human Genetics. "One explanation is that many genes are involved, none of which individually may have a major effect." At least ten genes - and possibly as many as a 100 - are hypothesized to be involved in autism, she said.
"In addition, autism may stem not from the effects of single genes, but rather from the interaction of particular genes, or sets of genes, when they come together in certain combinations," Pericak-Vance added. The analytical method applied by the researchers allowed them to rigorously test for the role of such gene combinations in autism for the first time, she said.
The researchers reported their findings in the September issue of The American Journal of Human Genetics (available online August 3, 2005). The work was supported by the National Institutes of Health, the National Alliance of Autism Research, and the Hussman Foundation. Resources were also provided by The Autism Genetic Resource Exchange, a program of Cure Autism Now.
In recent years, the number of children diagnosed with autism in the United States has skyrocketed, the researchers noted. One of the most heritable of complex genetic disorders in neuropsychiatry, autism is characterized by impairments in social interaction and communication and restricted and repetitive patterns of interest or behavior.
While many previous studies have identified possible genes with links to autism, there remains no single gene with a consistent connection to the disease, Pericak-Vance said.
Multiple lines of evidence, including alterations in levels of GABA and GABA receptors in patients with autism, have implicated the brain mechanism in the disease. Furthermore, there is evidence that GABA plays a key role in the early development of the brain.
Earlier research by the Duke team and other researchers linked a portion of chromosome 15 to autism risk. That region harbors genes that code for three GABA receptors.
Since one of the primary functions of GABA is to inhibit nerve cells from firing, it plays a key role in telling the body to "slow down.". The GABA system therefore acts as a sort of information filter, preventing the brain from becoming over-stimulated, the researchers explained.
"Impairing the GABA system could overwhelm the brain with sensory information, leading to both the behavior and the pattern of cell damage that emerges in autism," said John Hussman, Ph.D., a study co-author and president of The Hussman Foundation, one of the groups that funded the study.
The researchers examined 14 genes that encode portions of the GABA receptor in 470 Caucasian families. Of those families, 266 included more than one person with autism and 204 included one autistic individual. The team tested for associations between particular gene variants and the disease. They also applied sophisticated statistical methods designed to zero in on the effects of particular gene combinations.
The researchers found that one of the GABA receptor genes, GABRA4, is involved in the origin of autism. Moreover, they report, GABRA4 appears to increase autism risk through its interaction with a second GABA gene, GABRB1.
"This is a key finding for our understanding of the complexity of interactions that underlie autism," Pericak-Vance said. "We can now apply the analytical approach to other genes that may play a role in the disease." Such findings may ultimately yield a method to screen for individuals at high risk for the disease, she added.
"The new findings offer important new information for families affected by autism about the complexity of the disease," said clinical psychologist Michael Cuccaro, Ph.D., a study co-author also of the Duke Center for Human Genetics.
Furthermore, he added, existing medications already target the GABA system, including diazepam (Valium®) and some anti-epileptic drugs. "As we begin to understand the GABA system as it relates to the neurological underpinnings of autism, we may advance toward new therapies."
Collaborators on the study include D.Q. Ma, P.L. Whithead, M.M. Menold, E.R. Martin, A.E. Ashley-Koch, G.R. DeLong and J.R. Gilbert, all of Duke; H. Mei of North Carolina State University; M.D. Ritchie of Vanderbilt University; and H.H. Wright, Ruth Abramson of University of South Carolina.
Kendall Morgan
kendall.morgan@duke.edu
919-684-4148
Duke University Medical Center
http://www.dukemednews.org
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