Today is World Autism Awareness Day, and was marked by a beautiful video from the UN secretary (with a little help from his friends) explaining why it’s so important that we all take a moment to understand children and adults living with autism. My favourite quote from the video- “When we join in the struggle to realise the rights of people with autism, we uncover greater humanity within ourselves and create a better society for all.” Wouldn’t that be a wonderful world to live in?
Because of this, we decided to write a post about Autism Spectrum Disorders (ASDs), trying to tackle some of the main symptoms of the disorder as well as the science behind it!
So what is Autism?
ASDs are a number of neurodevelopment disorders that are characterised by problems in social interaction and communication as well as repetitive behaviours. The spectrum is split up into a number of groups: Aspergers syndrome, autistic disorder, PDDs not otherwise specified, rett syndrome and childhood disintegrative disorder. Along with the social problems mentioned before, ASDs have some physical symptoms: Macrocephaly (abnormally large head), microcephaly (abnormally small head), increased brain weight/size and abnormalities in neuronal cells throughout the brain and nervous system.
What are the Causes?
1. Defects in Neuronal Development
Mutations in one of a number of genes has been shown to be important in the development of autism. Insulin like growth factors (IGFs), specifically IGF-I, have been implicated in ASDs due to their involvement in the PI3K/Akt/mTOR pathways in the body. These have important roles in protein synthesis, cell survival, cell growth and metabolism, to name a few. Defects in these converging pathways have been linked to development of ASD like behaviours, often stemming from defects in the nervous system and brain. Issues with neurone myelination are often seen in ASD children leading to problems with synaptic transmission and neuronal development. To put it simply, the brain is made up of billions of cells called neurons that transmit and process information throughout your body via the nervous system. Myelin is an electrically insulating protein which is wrapped around the axon of a neurone (the longest part of the cell) and is essential for speedy movement of action potentials throughout your body. In many ASD patients there is a loss of this myelin, so these signals are severely slowed or stopped completely meaning the information your brain is trying to send can be lost. This is why people with ASDs have problems with social skills and communication, tasks which require quick transfer of information to different areas of your brain and body.
Other candidate genes and effectors include reelin (RELN), human serotonin transporter (SLC6A4), gamma-aminobutyric acid receptor (GABR), neuroligin (NLGN), human oxytocin receptor (OXTR) and MET, among others. There is definitely a genetic aspect to ASDs, but interestingly there are other factors at play…
There is growing evidence that autism is not just caused by genetic defects, but can be affected by a child’s environment, supported by studies in twins. The first year of life is thought to be very important in development and severity of autism, with emphasis placed on parental age, low birth weight, multiple births and maternal infections during pregnancy.
3. Abnormalities in Immunity and Neuroinflammation
Defects in a number of important aspects of the immune system have also recently been linked to the development of ASDs. Some subgroups showed abnormalities in natural killer cells leading to a decrease in their cytotoxicity and cell killing ability. This ties into the fact that ASD patients have a higher risk of developing cancer. Variations in cytokines (proteins released by immune cells that influence how other cells react) have also been observed in patients with autism spectrum like behaviours, leading researchers to think there is more interplay between immunity and the nervous system than we currently realise.
The majority of what we know about Autism Spectrum Disorders relies on research into singular areas of the body. To fully understand the problem, our next task is to tie all of this information together to gain a real understanding of why these disorders occur, and how we can help those suffering with ASDs to become more self sufficient.
I’ve certainly learned a lot more about Autism from writing this article, I hope you’ve found something that interested you in reading it!
Chen J, Alberts I, & Li X (2014). Dysregulation of the IGF-I/PI3K/AKT/mTOR signaling pathway in autism spectrum disorders. International journal of developmental neuroscience : the official journal of the International Society for Developmental Neuroscience PMID: 24662006
Li, X., Zou, H., & Brown, W. (2012). Genes associated with autism spectrum disorder Brain Research Bulletin, 88 (6), 543-552 DOI: 10.1016/j.brainresbull.2012.05.017
Hallmayer, J. (2011). Genetic Heritability and Shared Environmental Factors Among Twin Pairs With Autism Archives of General Psychiatry, 68 (11) DOI: 10.1001/archgenpsychiatry.2011.76
Goyal DK, & Miyan JA (2014). Neuro-Immune Abnormalities in Autism and Their Relationship with the Environment: A Variable Insult Model for Autism. Frontiers in endocrinology, 5 PMID: 24639668