Autism Spectrum Disorder – an extremely serious neurodevelopmental disorder that usually impairs the ability to interact and communicate.
Recently, I had come across a TedTalk, by Wendy Chung, on Autism. The talk explored our current knowledge of ASD and how much more knowledge is yet to be discovered. I was absolutely intrigued by the facts revealed by Wendy Chung and was left flabbergasted and frustrated at the lack of knowledge we have of this disorder
As per Wendy Chung, ASD is not a single disorder, but a spectrum of disorders. Symptoms of ASD can range from a person who is not verbal, and can’t communicate at all, to a person who is a mathematical genius, a person who is remarkably gifted in maths but struggles to communicate to others and can’t keep eye contact. Both these two examples are diagnosed under the umbrella called ASD
I was curious about how much the symptoms of Autism vary. So, I had read a couple of NHS articles on the symptoms of autism. The severity of the symptoms of a person diagnosed with ASD depends on where the person lies on the spectrum, as ASD includes classic autism, Asperger’s syndrome and PDD (Pervasive Developmental Disorder). Some symptoms I read about on NIH articles included; echolalia or repetitive actions, or strong resistance to disruptions or changes to their schedule, and many also have difficulty in tolerating sensory stimuli like loud noises or bright lights. Another interesting symptom I had found out was that ASD also has the ability to affect one’s intellectual ability. An individual could have a mild to moderate intellectual ability while another could have an advanced intellectual ability.
According to the statistics presented by Wendy Chung the prevalence has increased from 1 in every 2000 during the 1980s to 1 in every 88 in 2012 to 1 in 68 just two years later. These worrying statistics caused me to wonder why there is such a big increase in the prevalence of autism. Has that number increased dramatically over time? However, my thoughts were filled with questions on whether the number of people with autism was increasing or if it was just due to the fact that we are now diagnosing more people with ASD. Since the range of symptoms is now much wider, and diagnosis being much more available, would that play a role in the increasing prevalence? In addition, the awareness of ASD has increased, which allows more to be tested and diagnosed with ASD.
Wendy Chung had also touched upon the causes of ASD. There isn’t a single cause of Autism but a range of etiologies. Many causes of ASD are yet to be discovered, but some of the causes that are proven to cause ASD is advanced paternal age and certain agents taken by the mother during critical stages of pregnancy. While the fetal brain is developing, exposures to certain agents like Valproic acid (A drug which is taken during epilepsy) is known to increase the chances of being diagnosed with ASD. Along with these factors, genetics also plays a huge role in ASD.
I wondered how big a role does genetics play when it came to the causation of ASD and so I had further researched on this topic and found out that heritability can account up to 90% in Autism from an article on JAMA Network.
Genetics plays a huge role in Autism and this was found through the concordance tests. Wendy Chung also spoke about the different concordance tests and why they were done. They had looked into three types of siblings for these concordance tests. The first being Identical twins or monozygotic twins which have the same DNA and the same intrauterine environment, the second type being fraternal or dizygotic twins who have 50% of the same genes and the same intrauterine environment, and the final type being siblings, who have 50% same genes but a different intrauterine environment.
In order to get a reaffirmation on what the concordance results were, and how much they differed between monozygotic and dizygotic twins, I found out after doing some research that the concordance rate for identical twins is 77% and the concordance rate of fraternal twins being 33%, which clearly emphasises that genetics does play a vital role when it comes to ASD.
Wendy Chung had also explained one of the biggest tests run by the company she worked at, which included around 2600 autistic children who were a part of this experiment. To obtain more information as to what genes play a role in Autism Simons Foundation had conducted an experiment, where they had 2600 autistic kids, who had no family history of autism at all. They had tried to find any de novo mutations that could have triggered or caused the autism. Problems started to occur when they found out that for some people, one single gene mutation ad caused Autism, unfortunately, this wasn’t the case for others. For others, a combination of gene mutation had caused ASD, which proves that a number of genes do play a role in Autism, rather than just one single gene.
I was absolutely intrigued by the fact that rather than one gene, multiple genes could come into consideration and was obliged to do some more research on this. After reading countless articles on OMIM, NIH and Science Direct, I found out that most people who are diagnosed with ASD only have a mutation in one gene, however, thousands are associated with autism. Some examples I had found are ARID1B, ASH1L, CHD2, CHD8, DYRK1A, ANDP, and many more. Most of these are genes that are involved in the development of the brain and affect many parts of the brain such as production, organisation, and growth of neurons. Some also affect the number of neurons that are produced, while others are involved in the development or function of the connections between neurons.
The first gene which I would like to expand on was the TBR1 gene. Recently, two individuals with the same de novo mutation in TBR1 who were both presented with severe intellectual disability and developmental encephalopathy. This was then further researched and is now is reported in Autism Spectrum Disorder.
Another gene that I had read about was the ANDP gene, which is a gene that provides the instructions for making a protein that helps to control the expression of other genes through chromatin remodelling. Expression of genes is extremely important as it controls whether or not that particular gene would be translated into RNA, explaining why this gene could be a potential cause of ASD. Another gene which was also associated with ASD, which also regulates gene expression through chromatin remodelling was CHD2.
Another gene that plays a major role is the ARID1B gene. ARID1B is an essential gene that makes the protein which forms a part of the SWI/SNF complex. Since the SWI/SNFF complex manages the actual changes in the structure of chromatin, it is directly involved in gene expression and chromatin remodelling. An interesting fact about this particular gene is that it is also a tumour suppressor and most autistic kids are found to have an abnormal growth in their brains which helps to prove that this gene does play a role in Autism.
Other genes like ASH1L and DYRK1A which also are associated with ASD are linked with the maturation of the brain and cells which are associated with the nervous system. The ASH1L gene plays an important role in the development of the brain as it turns on genes, which are associated with the development of the brain. DYRK1A, on the other hand, plays a role in the maturation of dendrite spines from dendrites. This directly links with the communication of cells in the brain, and are linked with the nervous system.
After digging through the internet, I found out that most of the genes associated with autism are linked to gene expression and epigenetics. This made me curious as to whether the reason why the concordance result for monozygotic twins is less than 100%. Could it be due to epigenetics, since epigenetics takes both the environmentality and heritability into consideration?
Since ASD has a very high heritability rate, I was wondering how do we intervene? How could we help and treat children with autism? On the Ted Talk, Wendy had talked about interventions as a combination of factors, one of the most important being early detections. I was absolutely elated by the fact that many people are now attempting to use modern technology, that we now have access to, to allow early diagnosis. Ami Klin has developed a method in which by using biomarkers, we can track infants’ eye contact. Since one of the most common symptoms of autism is the lack of eye contact, when someone sings a nursery rhyme, we can check whether or not that baby is making good eye contact. By this method, we can detect early symptoms of ASD. I had searched up why early detection was so very important. One interesting fact I came across was the fact that during the early stages, the brain has still not matured and is developing. Due to this, early treatment can create a huge impact on the infant’s brain, being extremely helpful. Wendy Chung had also briefly mentioned other forms of intervention like drugs and medicines. Medication can be used to reduce or tame the symptoms of ASD. We can also use different educational strategies. Autistic kids see differently; absorb their surroundings differently; and learn differently.
With new technologies being invented, new treatments being discovered, the awareness of Autism Spectrum Disorder is increasing. Our knowledge in this area is increasing at a rapid rate, but much to our dismay, a large proportion is yet to be discovered. Genetics is a subject that was only recently, around the late 1900s, been discovered, yet we are making such great discoveries. Let us hope that with more research, more technological advances and more knowledge, we will be able to conquer and understand more about the disorder known as Autism Spectrum Disorder.
- ShubangiP