What Genes Are Causing Autism?

The physiologist from the University of Washington, Raphael Bernier and geneticist Evan Eichler started their research on genes that cause autism in late 2013 when they became interested in a 12-year old girl’s case. Bernier noticed that the girl had wide-set eyes, which had a slight downward slant. Her head was unusually large, featuring a prominent forehead. He was told that the girl had gastrointestinal issues and sometimes wouldn’t sleep for two to three days at a time. He probably wouldn’t have thought too much of this case had he not recently met an 8-year old boy with those similar wide-set eyes and a large head who also suffered from the same gastrointestinal and sleep problems.
While there were definitely other children with the similar physical peculiarities, there was one more similarity that couldn’t be considered a coincidence: a mutation in a gene known as a chromodomain helicase DNA binding protein 8 (CHD8).
CHD8 produces a protein that regulates chromatin—the conglomeration of tightly packed DNA and proteins in the nucleus—during fetal development. Bernier continued his studies and reviewed records from 25 such children from different countries. They all had similar physical symptoms. Mutated CHD8 is now one of the dozens of recognized genetic subtypes of autism.
However, not all forms of autism are caused by genetic mutations. There are also numerous non-genetic factors that contribute, such as environmental pollution, which can affect the brain of a child. Scientists are working towards a better understanding of neural development to give us an answer on what exactly causes autism.
And thanks to advances in induced pluripotent stem cell (iPSC) technology, scientists can now grow entire brain-like structures (organoids) derived from cells of patients with autism.
Last year, Yale University’s Flora Vaccarino and her colleagues reprogrammed skin cells from boys with autism who had abnormally large heads—a condition known as macrocephaly, a relatively common phenotype in autism patients—into iPSCs (the stem cells mentioned above) and then differentiated the cells into neurons. Under special culturing conditions, the cells developed into 3-D organoids— mini brains —that mimicked forebrain development at about 10 to 16 weeks post-conception. The researchers also created organoids using the cells of the boys’ healthy fathers, and compared them to the structures derived from the boys’ cells. (See “Mini Brains Model Autism,” The Scientist, July 16, 2015.)
In conjunction with this study, there has been a recent study in France that showed that brain maturation was disrupted and certain portions of the brain seemed to be wasting away in areas responsible for communication. Also, a neurologist of Harvard Medical School and Boston Children’s Hospital, Mustafa Sahin, noticed that children with a rare genetic disorder called tuberous sclerosis (TSC), where they develop benign tumor growths in the brain and other vital organs, develop autism 50% of the time. All these studies aim at being able to treat a child likely to have autism before the disease develops.
While this is a lofty goal, methods are already in the works with University of Washington planning a clinical trial to treat mice with a medication that repairs sodium channel disruptions and with Boston Children’s Hospital working to study a tumor suppressor in the body that has been linked to macrocephaly and language and social impairments.
The results thus far have mainly confirmed the suspicion that there is not one single form of autism but many, and the different subtypes have to be identified before we can develop specific treatments for each. While there is still no treatment for any one form of autism there is the hope that if we get even one, it is very possible that we will be able to more easily find cures for all the others.

To Read More: http://www.the-scientist.com/?articles.view/articleNo/46659/title/The-Genes-Underlying-Autism-Are-Coming-Into-Focus/

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