Genetics

Autism May Involve Disordered White Matter in the Brain

Source: 
Science Daily
Abstract: 

While it is still unclear what's different in the brains of people with autism spectrum disorders, more and more evidence from genetic and cell studies points to abnormalities in how neurons connect to each other.

Another Genetic Clue To Autism: Opposite Malfunctions Have Same Result

Source: 
Medical News Today
Date Published: 
November 25, 2011
Abstract: 

In most cases, autism is caused by a combination of genetic factors, but some cases, such as Fragile X syndrome, can be traced to a variation in a single gene that causes overproduction of proteins in brain synapses. Now a new study led by the same MIT neuroscientist who made that discovery, finds that tuberous sclerosis is caused by a malfunction at the opposite end of the spectrum: underproduction of the synaptic proteins.

Mutations Causing Syndromic Autism Define an Axis of Synaptic Pathophysiology

Source: 
Nature
Date Published: 
November 23, 2011
Year Published: 
2011

New research reveals that two genetic forms of autism, fragile X syndrome and tuberous sclerosis, are actually caused by opposite malfunctions – while fragile X is caused by overproduction of proteins at the synapse, tuberous sclerosis is caused by underproduction. Interestingly, while the causes of fragile X and tuberous sclerosis are distinctly different, both disorders often result in intellectual disability and autism spectrum disorder. Researchers made the discovery while studying mGluR5 (Metabotropic glutamate receptor 5), a receptor on the surface of neurons that is key in aiding communication at the synapse – the junction between neurons. During normal signaling, the mGluR5 receptor binds to the neurotransmitter glutamate after it is released across the synapse, resulting in the production of new synaptic proteins. Fragile X protein (FMRP) halts protein synthesis to ensure that the appropriate amount is produced -- in fragile X syndrome, changes to the gene that controls FMRP allow synaptic proteins to continue production unchecked, resulting in too much protein. Researchers have previously shown that introducing a substance to block mGluR5 reverses some of the symptoms of fragile X, and human drug trials are currently underway. Armed with an understanding of the underlying causes of fragile X, researchers in this study examined mice with tuberous sclerosis mutations and discovered something surprising. In this case, the disorder was caused by the opposite malfunction – too little protein synthesis at the synapse, which could be treated with a drug stimulating mGluR5. Further, when the researchers bred the two mice together, many of their autistic features went away. The findings of the study indicate that proper brain function can only occur within a narrow range of mGluR5 protein synthesis – changes in either direction lead to syndromes with similar behavioral symptoms. This also suggests that drug treatments for autism spectrum disorder will need to be individually tailored, as conditions that appear similar may have quite different underlying causes.

--IACC 2011 Summary of Advances in ASD Research

How Brain's Structure And Genes Affect Autism And Fragile X Syndrome

Source: 
Medical News Today
Date Published: 
November 17, 2011
Abstract: 

Research just released shows that scientists are finding new tools to help understand neurodevelopmental disorders like autism and fragile X syndrome.

Researchers debut SHANK2 mouse, SHANK3 rat

Source: 
SFARI
Abstract: 

Researchers debut the SHANK2 mouse and SHANK3 rat at the 2011 Society for Neuroscience annual meeting. SHANK2 belongs to the same family as SHANK3, a well-established autism candidate gene.

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.