I have seen something about Epigenetics twice in one day, I am sharing this in the hopes that it might help someone improve their diagnosis….
DNA is like an instruction manual in creating all parts of our body. It sounds pretty simple, the body just follows these instructions and we grow and develop based on DNA, right? Only halfway right.
The DNA portion of the markup is unchangeable. It’s a firm plan. The DNA in our bodies are wrapped around Histones, a protein. Attached to the histone and DNA are other chemical tags called Epigenomes. While DNA itself isn’t able to be changed or modified, epigenomes are reactive based on external factors like diet, stress, and environmental factors. The epigenome adjusts genes based on what we are subjected to around us.(1)
It is widely believed that Autism Spectrum Disorders are genetic. However, there is also reason to believe that some of the factors of how the disorder affects someone can be traced to epigenomes, and how environmental elements affect them. There are several chromosomes that have been traced to cases of Autism. (2)
Studies suggest that there is a connection between Autism / ASD and the chromosomes 15Q, 7Q, and X.
Duplications of chromosome 15Q (11-13) are commonly recurrent cytogenetic aberration associated with ASD. This occurs in 5% of patients with Autism Spectrum Disorders. The 15Q (11-13) chromosome is responsible for normal neurodevelopment. The duplication of this chromosome is dependent on which parent the allele is derived from. Duplications in the maternal copy of this chromosome have been found to result in more cases of Autism. Overexpression of maternal genes is believed to be a cause of Autism. (2)
With chromosome 7, it has been found that changes in the number or structure of chromosome 7 (We normally have 2 copies of this chromosome), can causes delayed growth, mental disorders, and delayed speech. (3)
In the case of the x-chromosome, it’s important to note that there is a distinctive gender bias when it comes to Autism. There are 4 times as many males affected by Autism/ASD than there are females.
Based on the results of a study on females with Turner syndrome, a hypothesis involving epigenetic mechanisms was proposed to help describe the gender bias of ASD. Turner syndrome patients have only one X chromosome which can be either maternal or paternal in origin. When 80 females with monosomy X were tested for measures of social cognition, the patients with a paternally derived X chromosome performed better than those with a maternally derived X chromosome. Males have only one X chromosome, derived from their mother. If a gene on the paternal X chromosome confers improved social skills, males are deficient in the gene. This could explain why males are more likely to be diagnosed with ASD. (4)
(2) Schroer R.J., Phelan M.C., Michaelis R.C., Crawford E.C., Skinner S.A., Cuccaro M., Simensen R.J., Bishop J., Skinner C., Fender D., et al. Autism and maternally derived aberrations of chromosome 15q. Am. J. Med. Genet. 1998;76:327-336.
(3) Schanen N. C. (2006). “Epigenetics of autism spectrum disorders”. Human Molecular Genetics 15: R138–R150.
(4) Skuse, D.H., James, R.S., Bishop, D.V., Coppin, B., Dalton, P., Aamodt-Leeper, G., Bacarese-Hamilton, M., Creswell, C., McGurk, R. and Jacobs, P.A. (1997). “Evidence from Turner’s syndrome of an imprinted X-linked locus affecting cognitive function”. Nature 387 (6634): 705–708.