Understanding Genetics: Chromosome 7

Links to chromosome 7 and its relation to Autism, date as far back as approximately 1999. According to Science Daily, in 2003, chromosome 7 became the largest human chromosome to be sequenced. The Washington University School of Medicine in St. Louis along with approximately five other centers completed the sequencing of approximately 1,150 genes on chromosome 7. With ties to language controls, chromosome 7 additions and deletions have adverse effects on health in many different ways and are frequently seen in human cancer sufferers.

Deletion of a chromosome 7 sequence, 7Q11.23 leads to Williams Syndrome. This genetic condition affects approximately 1 in 10,000 people worldwide and approximately 20,000-30,000 people in the United States are believed to suffer from Williams Syndrome. This condition occurs equally among males and females. These individuals are very social and friendly, some describe them as "friendly to the extreme", but they may have life-threatening cardiovascular problems and may need speech and occupational therapy. These individuals suffer from difficulties with spatial relationships, numbers, abstract reasoning, and as babies may have feeding problems and colic. The comedian, popularly known as Carrot Top, is rumored to have Williams Syndrome. Orlando Bloom had been rumored to have Williams Syndrome, but this is denied by multiple news outlets. I would invite you to visit the blog of the little girl pictured below. Her name is Lauren and she has been diagnosed with Williams Syndrome.

Lauren's World

In 2010 Yale University School of Medicine searched the DNA of more than 1,000 individuals with Autism and their unaffected family members. Among the 400 suspected genome sites they discovered that maybe related to Autism, they found the correlation between chromosome 7 and Autism. A duplication of the same segment of chromosome 7 that impacts William's Syndrome is associated with Autism and antisocial behavior. Nature published the findings in 2011. 

Researchers in the SFARI network believe there maybe links to chromosome 7 and epilepsy, as well as Autistic-like behavior. In 2005 a team of researchers identified the first duplication case. The study included 27 children who were originally seen for a range of varying issues. This team identified the duplication in these participants and determined these subjects had a range of speech related issues. The lead researcher, Mervis, expressed her skepticism of the appropriate nature of an Autism diagnosis since these children are skilled in pretend play and gesture communication. Her findings are further supported by a study conducted in 2007, which reported that people with the duplication tend to be referred for Autism, but do not meet diagnosing criteria. It is important to note that those with duplication of chromosome 7 vary in impact, which insinuates that other genes are involved, depending on the "symptoms" exhibited by the sufferer. Mervis estimates that up to 30% of her testing group inherited the duplication from their parents, who also had a history of speech problems and a high rate of social phobias, resembling anxiety. 

As recently as 2010 studies have also been conducted on another part of chromosome 7, known as AUTS2, and published by Opening Autism. Deletion of AUTS2 is caused by a loss of genetic material on chromosome 7. This loss has been associated with features of Autism as well as intellectual delay and even seizures. These symptoms are also likely to range in severity in each individual. Researchers admit that deletion of AUTS2 is not commonly tested for, so it is difficult to know how many individuals suffer from this missing sequence. It is worthy to note that individuals with the AUTS2 deletion have decreased muscle tone, which is a common feature of Autism, which can lead to feeding issues and developmental delay. Eye abnormalities are also commonly reported among those suffering from AUTS2 deletion, along with hearing loss, short stature, and seizures. So far no cure is available for AUTS2 or other chromosome 7 afflictions. 

To read more about chromosome 7 and related health issues, please see this article.

To read more about chromosome 7 and its relevance to Autism, please see this article. 

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