In the medical world of today, breakthroughs continually occur which reveal, piece by piece, the causes of conditions that have plagued the human race for decades. The neurodevelopmental disorder, Autism, diagnosed in 6 out of every 1000 children is one such case.[i] Causing severe, life long problems with the social and communication skills of the individual affected, researchers have for many years been striving to find the key to understand this complex genetic disorder.i
In a two year study, researchers at The Simons Centre for Systems Biology used single nucleotide polymorphism genotyping chips to compare the genomes of the individuals being studied in order to locate possible differences and therefore identify genes that may be linked to autism.[iii] Single nucleotide polymorphisms (SNPs) occur when one base is replaced at the same point along the locus with one of the three other bases used to construct DNA.[iv] This is seen below in Figure 2.
Figure 2: [v]
They most commonly occur in regions of DNA between coding genes and therefore are believed to have little or no effect on the function of the organism.iv However when they occur within the coding gene or in regulatory areas that control gene activity, there is a greater possibility that they affect the expression of the gene and are involved in causing a condition.iv
Over 800 families, each having two or more autistic children were studied and the results compared with the results of a control group of non-autistic individuals.iii The research identified four genes as having a significant connection with autism. NRXN1 and CNTNAP2, two genes that code for proteins located in neurons in the central nervous system, had been known to have an associated with autism.iii However two other genes, NCAM2 and PTPRD, which code for proteins found in neurons in the central nervous system were also linked to autism by comparing the variations in the genomes of the autistic children with that of the control group.iii Figure 3 below shows a deletion in the NCAM2 gene of a child with Autism.
The study also found a link with the p53, p63 and p73 family of genes.iii The number of SNPs within the coding region for genes p63 and p73, genes which ensure the genetic information being given to the eggs in females is correct, was significantly greater in mothers with autistic children than the control group.iii In faulty p63 and p73 genes, the incorrectly coded protein will often fail to work properly, therefore allowing errors in the DNA to be given to the egg. This in turn may result in conditions such as Autism.iii
Throughout the study, no common gene mutation was found between the parents and the autistic child.iii This led to the conclusion by researchers that autism in offspring may be caused by a single nucleotide polymorphism in the parent that causes certain genes being given to the egg or sperm to have errors.iii This theory in regards to Autism may be applicable to other genetic disorders and it is hoped by researchers, will lead to diagnostic tests, possible prevention and gene-based treatments for Autism and many other genetic disorders in society.iii
[i] National Institute of Neurological Disorders and Stroke. (2012). Autism Fact Sheet. Viewed 17th March 2012. Available: http://www.ninds.nih.gov/disorders/autism/detail_autism.htm
[ii] Project Wellness. (2012). Autism, ADHD, ADD and Inflammation: Part 1. Viewed 18th March 2012. Available: http://projectwellness.com.au/nutrition/autism-adhd-addd-and-inflammation-part1/
[iii] Chan. C, Christen. S, Naqvi. A. (2010). Identifying Novel Genes Associated with Autism. Viewed 15th March 2012. Available: http://www.ias.edu/about/publications/ias-letter/articles/2010-fall/autism
[iv] Genetics Home Reference. (2012). What are single nucleotide polymorphisms? Viewed 17th March 2012. Available: http://ghr.nlm.nih.gov/handbook/genomicresearch/snp