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Epigenetics is the study of how DNA expression is controlled. DNA is stored by being wrapped around proteins called histones. The histones have different arms that can be modified, normally by the addition of a methyl group, a phosphate group, or an acetyl group. When specific points on the histone arms are modified, the DNA is either more tightly wound around the histone, which results in decreased gene expression, or the DNA is opened up, resulting in increased gene expression. Epigenetics can help explain why individuals with the same genes may have different expression patterns. Epigenetic changes may even be heritable, meaning they can be passed from parent to offspring. The changes caused by the different histone modifications can be induced by environmental factors. In addition, the changes may be reversible, although scientists have not fully discovered how to do this in cells.

Autism spectrum disorder is a series of disorders associated with symptoms involving difficult social interactions, repetitive behaviors, and impaired language development. Different patients that have been diagnosed with autism have varying levels of severity of the disease, and may present with different symptoms in the three affected areas. The incidence of autism spectrum disorder has increased significantly in recent years. This may be in part due to improved diagnostic standards, and a larger range of symptoms included in diagnosis. Indeed, many patients who have been diagnosed with Autism in recent years would not likely have been diagnosed many years ago due to the different standards.

A genetic component has been associated with the development of autism spectrum disorders. A major piece of data supporting the hypothesis that Autism spectrum disorders have a genetic component comes from data from identical twins. If one identical twin has autism spectrum disorder, the other twin has a 70% chance of also having autism spectrum disorder. However, this also means that if one identical twin has Autism spectrum disorder, there is a 30% chance that the other twin does not. This implies some type of environmental or non-genetic component to the disease.

Researchers from King’s College London examined DNA histone methylation at 27,000 sites in the genome from fifty sets of identical twins. Methylation of the histone proteins generally results in decreased expression of the DNA. Out of the fifty sets of twins studied, eleven pairs were both healthy, five pairs both had autism spectrum disorder, and the remaining thirty four pairs had different autism spectrum disorder diagnoses. The research team found patterns they were able to link to both the diagnosis of autism spectrum disorder as well to the severity of the disease. In all of the patients that had an autism diagnosis, specific sites in the DNA had histone methylation. In addition, different symptoms of autism spectrum disorder were linked to methylation at specific sites of the genome. Some of these sites occurred at locations associated with early brain development and the development of autism spectrum disorder, which may be contributing factors to autism.

The research into epigenetic modifications at specific locations in the genome is a big breakthrough in autism research. Because some of the epigenetic histone modifications can be influenced by environmental pressures, this research helps bridge the gap between a genetic cause of autism spectrum disorder and an environmental cause. This information could help improve diagnosis of autism spectrum disorder, helping clinicians find more definitive data in determining their diagnoses. Clinicians could diagnose autism earlier in some patients, or perhaps even find interventions to help delay the progression of the disorder. Early diagnosis and therapy for autism spectrum disorder results in better outcomes for the patients. In addition, because epigenetic changes may be reversible, it is possible that researchers might find ways to help reduce the symptoms associated with autism. While scientists do not fully understand exactly how histone modifications occur, or what causes them, research is constantly advancing and this information may one day be available. If scientists can manipulate the genes affected by histone modification in autism, they might be able to provide therapeutic benefits in this manner as well. The research linking specific epigenetic histone methylation to autism symptoms and disease severity indeed will be followed by many groundbreaking advancements in autism research. With the rising incidence of autism, these advancements will be very welcome to many parents and patients alike.


References:

http://www.sciencedaily.com/releases/201...091113.htm