Genetics

Genetic Heritability and Shared Environmental Factors Among Twin Pairs with Autism

Source: 
Archives of General Psychiatry
Date Published: 
November 2011
Year Published: 
2011

Recent research suggests that environmental factors may play a much greater role in autism risk than previously suspected and could even be more influential than genetic factors. These findings stem from a study of autism in twins, the largest of its kind, designed to model the genetic and environmental factors that contribute to the development of autism. Because identical twins share 100 percent of their DNA, researchers can assess the degree to which a disorder is genetic by studying the number of cases where both twins are affected (called concordance). Fraternal twins share 50 percent of their DNA, similar to siblings, so by comparing concordance rates among fraternal twins and siblings, researchers can study the influence of environmental factors, particularly those in the womb. In the study, researchers looked at concordance among 192 pairs of identical and fraternal twins and found that 77 percent of male identical twins and 50 percent of female twins were both affected by autism. Previous studies with smaller numbers of twins suggested a much greater genetic contribution, as high as 90 percent. The fraternal twins in the study had a 35 percent concordance rate – much lower than rates among identical twins but higher than rates among siblings, estimated to range from 3 to 19 percent. Using mathematical modeling, the researchers propose that environmental factors accounted for 55 percent of autism risk, while genetic heritability contributed less than 40 percent. The difference in rates among fraternal twins and siblings, who share similar amounts of DNA, suggests that environmental factors in the womb may be an important area of future study.

--IACC 2011 Summary of Advances in ASD Research

TBL1X Gene Involved In Autism Spectrum Disorder

Source: 
Medical News Today
Date Published: 
November 6, 2011
Abstract: 

TBL1X Gene Involved In Autism Spectrum Disorder: Dr. Eden Martin from the Hussman Institute explains, "The SNP in TBL1X is associated with an increase in risk for ASD of about 15%.

Study In Fruit Flies Has Implications For Autism, Other Cognitive Impairment Syndromes

Source: 
Medical News Today
Date Published: 
November 1, 2011
Abstract: 

Loss of FMR1 function is the most common genetic cause of autism. Understanding how this gene works is vital to finding new treatments to help Fragile X patients and others...

Having A Child With Autism Linked To Genetic Variant And Autoantibodies: Finding May Lead To Screening Test

Source: 
Medical News Today
Date Published: 
October 20, 2011
Abstract: 

A study by researchers at UC Davis has found that pregnant women with a particular gene variation are more likely to produce autoantibodies to the brains of their developing fetuses and that the children of these mothers are at greater risk of later being diagnosed with autism.

Common Form Of Autism Recreated In New Mouse Model

Source: 
Medical News Today
Date Published: 
October 7, 2011
Abstract: 

Research team from Beth Israel Deaconess Medical Center (BIDMC) has created a genetically engineered mouse with increased dosages of the Ube3 gene. And, like the patients who also harbor increased dosages of this single gene, the genetically engineered mice exhibit robust examples of all three traits considered hallmarks of autism: reduced social interaction, impaired communication and excessive repetitive behaviors. Findings provide further clues in understanding the brain defects that lead to the development of autism, and offer an important tool for future use by scientists and clinicians to test possible drug therapies.

Evidence found for the genetic basis of autism: Models of autism show that gene copy number controls

Source: 
Science Daily
Date Published: 
October 5, 2011
Abstract: 

Scientists at Cold Spring Harbor Laboratory (CSHL) have discovered that one of the most common genetic alterations in autism -- deletion of a 27-gene cluster on chromosome 16 -- causes autism-like features. By generating mouse models of autism using a technique known as chromosome engineering, CSHL Professor Alea Mills and colleagues provide the first functional evidence that inheriting fewer copies of these genes leads to features resembling those used to diagnose children with autism.

Absence of CNTNAP2 Leads to Epilepsy, Neuronal Migration Abnormalities, and Core Autism-Related Deficits

Source: 
Cell
Date Published: 
September 30, 2011
Year Published: 
2011

A new mouse model of autism, created by eliminating a gene strongly associated with the disorder in humans, shows promise for understanding the biology that underlies ASD and testing new treatments. By eliminating the CNTNAP2 gene (contactin associated protein-like 2), researchers were able to create mice with behaviors that closely mimicked those of its human counterparts – the mice exhibited repetitive behaviors, abnormal social interactions, and irregular vocalizations, in addition to experiencing seizures and hyperactivity. CNTNAP2 is thought to play an important role in the development of language, and variants of the gene have been linked to an increased risk of autism and epilepsy. Prior to experiencing seizures, the mice showed signs of abnormal brain circuit development – researchers observed irregularities in communication between neurons and their migration within the brain. These observations complement earlier studies suggesting that children with autism carrying a CNTNAP2 variant have a "disjointed brain." The frontal lobe is poorly connected with the rest of the brain but shows an overconnection with itself, resulting in poor communication with other brain regions. Notably, the mice in the study responded positively to risperidone, an antipsychotic medication approved by the FDA to treat symptoms of irritability and aggression associated with ASD. While their social interactions did not improve – risperidone has not been shown to improve social function in humans – there was a marked improvement in repetitive grooming and a decrease in hyperactivity. Creating an animal model of autism that closely resembles the symptoms and behaviors in humans may be an important tool in understanding neural development in autism and developing new treatments.

--IACC 2011 Summary of Advances in ASD Research

'Autistic' mice created – and treated

Source: 
New Scientist
Date Published: 
October 3, 2011
Abstract: 

A new strain of mice engineered to lack a gene with links to autism displays many of the hallmarks of the condition. It also responds to a drug in the same way as people with autism, which might open the way to new therapies for such people.

Animal Model Research Could Lead To The Development Of Diagnostic Tests For Autism Based On Biomarkers

Source: 
Medical News Today
Date Published: 
September 14, 2011
Abstract: 

The first transgenic mouse model of a rare and severe type of autism called Timothy Syndrome is improving the scientific understanding of autism spectrum disorder in general and may help researchers design more targeted interventions and treatments.

Children With Autism And Gastrointestinal Symptoms Have Altered Digestive Genes

Source: 
Medical News Today
Date Published: 
September 11, 2011
Abstract: 

Researchers at the Center for Infection and Immunity (CII) at Columbia University's Mailman School of Public Health and at the Harvard Medical School report that children with autism and gastrointestinal disturbances have altered expression of genes involved in digestion. These variations may contribute to changes in the types of bacteria in their intestines.