Sunday, July 27, 2014

Understanding Genetics: Chromosome 17

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There is a lot of buzz on the internet around Chromosome 17. Some researchers believe this chromosome holds the key to the "cure" for Autism. Let’s be clear on that. There is no cure for Autism and some individuals with Autism are atimately against being "cured" since Autism is not a disease or sickness, but a disorder. I am not the one insinuating that Autism should or should not be cured I am simply discussing the information I have found on this topic. I ask that we all maintain respect for each other's personal Autism journey's and refrain from passing judgment on each personal situation.  
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Chromosome 17 contains approximately 81 million DNA building blocks. There are many disorders associated with chromosome 17; in fact the list is the greatest I have seen during this series. A deletion of a particular gene on chromosome 17, a variant called CACNA1G, is strongly linked to Autism.

CACNA1G is responsible for the regulation of calcium into and out of cells. Nerve cells in the brain rely on calcium to become activated; calcium to a nerve cell is like the starter for an engine. Imbalances in this procedure can result in an over stimulation of neuron connections and can create developmental problems, like Autism and in some cases epilepsy. 

A 2009 Time Magazine article discusses a study conducted by UCLA. Using the Autism Genetic Resource Exchange (AGRE), this contains genetic information from 2,000 families with at least one Autistic child. Using 1,000 of these samples from families with one son affected by ASD the researchers identified a region of chromosome 17 that contained genetic variants more common in boys than girls. One variant of CACNA1G is found more commonly in boys than girls. Researchers caution that though there is a strong genetic link in this region this is not the only region we should be concerned with. It simply means that more genes in this particular region are contributing to Autism. 

In November 2010 two articles were released about the connection between chromosome 17, Autism and Schizophrenia. Livescience published an article from Emory University. Researchers indicate that people who possess a specific change in chromosome 17 are 14 times more likely to develop ASD or schizophrenia than the typical population. The specific change researchers are referring to is a deletion of a particular section of chromosome 17 and this deletion is only found in individuals with ASD or schizophrenia. Researchers are clear that not everyone with ASD or schizophrenia have this deletion, but that all people with this deletion do have these disorders in some form. Researchers looked at the genetic makeup of approximately 15,749 people with developmental delay, intellectual disability and ASD. They found that 18 of these individuals had the deletion, compared to none of the 4,519 healthy controls. After identifying these 18, researchers found and interviewed nine of them. All nine had cognitive impairments and six had Autism. Researchers then studied the genetic information in two other databases of 7,522 people with Autism or schizophrenia and found the deletion again in two people with ASD and four adults with schizophrenia. Their control group of 43,076 individuals did not have the deletion. US News also published these findings, which were also published in the American Journal of Human Genetics. 

The research into the area is ongoing. It is apparent that chromosome 17 has a role to play in the impact of human genetics on Autism. 

This concludes the series Understanding Genetics. I hope this has shed light on an issue so little understood in its impact on our loved ones. The quest to understand our Autism journey comes from all aspects of our walk; this is just one part of that walk.

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