Chromosome 5 and Autism Connection
If you’re like the majority of the population you’re not exactly a master at all of the technical terms that are thrown about in studies of various treatments for Autism. Whenever I do any kind of article reading, I’m sure to have my search engine open and ready to go, in order to find the “layman’s terms” for different words and medical jargon. Truth be told, it’s a lot
A new study of chromosomes has found a connection between chromosome 5 and Autism. Great, right? But, what does it all mean?
What’s a Chromosome? The need-to-know basics.
Chromosomes are found in the cell nucleus and consist of long chains of nucleic acids coated with protein. Each chromosome contains hundreds or thousands of the genes that form our hereditary blueprint. Humans have 23 pairs of chromosomes, 46 total. Each parent contributes 1 chromosome to each pair.
Each chromosome has genes that determine almost every detail about us as a person. For example, some of the genes that are located on Chromosome 5 are Pikachurin – which is responsible for the eye’s ability to track moving objects; FGFR4 which is the fibroblast growth factor receptor, and SMN1 and SMN2 -the survivor motor neurons.
Chromosome Disorders
Chromosome disorders occur if there is an alteration in the number of chromosomes in the nucleus of a cell, or if there is an alteration of the structure of a chromosome. One of the chromosomes that researchers have looked at in depth recently is chromosome 5.
Chromosome 5 represents almost 6% of the total DNA in cells. Changes to chromosome 5 have been linked to certain types of cancers and Chron’s Disease. A recent study suggests that chromosome 5 may play a major role in Autism cases as well.
Chromosome 5 and Autism – The Connection
An in-depth genetic scan of Autism families found an area on chromosome 5 that is strongly associated with Autism. In the October 2009 issue of Nature, it was also said that there were two genomic areas that may harbor typically rare variants relevant to Autism.
There have been previous studies on how genes and chromosomes may affect Autism. These studies have found possible links on chromosomes 15, 16 and 5, but this is the first study that has concentrated the area of chromosome 5 to the 5p15 region. The study has found that a specific gene, SEMA5A (or semaphorin 5A), that is responsible for enabling neurons to their targets, may have a role in Autism Disorders.
For this particular study, the genomes of 1,031 families were examined. Furthermore, each family was considered a ‘multiplex’ family, or, families with multiple members with Autism Disorders. One method of study that took place was comparing the genes and chromosomes of the family members with the disorder to find like variants. The other method concentrates on comparing people with the disorder with people without the disorder to find similarities and differences to better understand where some causes of the disorder may lie.
A combination of these methods allowed researchers to discover that chromosomes 6 and 20 are significantly linked with Autism. Additionally, another area on chromosome 5 was found to carry a link as well. The new area or nucleotide is in very close proximity to SEMA5a. The variant is protective. In other words, it’s presence decreases the risk of Autism
Despite previous proof that Autism is a hereditary disorder, the genetic scan turned up very few genetic markers. It is believed by many that a mix of common variants that are prominent in 5% of the population as well as some rare variants are more contributory to Autism.
Bottom line – What does this all mean?
Simply put, this means that research is progressing and the causes of Autism are becoming more and more discoverable. Causes, after all, are the first step to finding a treatment. Because Autism truly is a puzzle of a disorder, finding one universal treatment may not be right around the corner. However, the more we find links to the cause, the more treatments we can find that satisfy what particular “form” of Autism is affecting our loved ones.
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Chromosomal abnormalities in the form of aneuploidy, are common among the people. About 8 percent of all conceptions are aneuploidy, and it is estimated that up to half of all abortions due to some kind of chromosome disorders.
also Autism is linked to the Paternal side of the family since the men determine the sex women determine how many.
Although autism is a highly heritable neurodevelopmental disorder, attempts to identify specific susceptibility genes have thus far met with limited success1. Genome-wide association studies using half a million or more markers, particularly those with very large sample sizes achieved through meta-analysis, have shown great success in mapping genes for other complex genetic traits. Consequently, we initiated a linkage and association mapping study using half a million genome-wide single nucleotide polymorphisms (SNPs) in a common set of 1,031 multiplex autism families (1,553 affected offspring). We identified regions of suggestive and significant linkage on chromosomes 6q27 and 20p13, respectively. Initial analysis did not yield genome-wide significant associations; however, genotyping of top hits in additional families revealed an SNP on chromosome 5p15 (between SEMA5A and TAS2R1) that was significantly associated with autism (P = 2 10-7). We also demonstrated that expression of SEMA5A is reduced in brains from autistic patients, further implicating SEMA5A as an autism susceptibility gene. The linkage regions reported here provide targets for rare variation screening whereas the discovery of a single novel association demonstrates the action of common variants.
I learned all this already when my 7 year old then 4 went threw Genetic testing.
Very interesting article! It is always great to hear about new advancements in finding the cause. I write blogs at http://www.myspeechtherapycenter.com and am always thrilled to share new findings with our community. Feel free to visit our site!