Autism Spectrum Disorder (ASD) is a complicated condition with an unknown cause and no definitive treatment. Scientists believe that ASD is in part genetically inherited in addition to environmental factors. In fact, hundreds of gene variants have been linked to autism, but their consequences are highly variable and some are related to other syndromes. New advancements in genetics research suggest that there may genetic causes that physicians are able to target now.
What is autism?
Autism is a disorder that is characterized by difficulty with social interaction, emotional processing, and sensory processing. As a spectrum disorder, some patients are high- functioning, meaning they may only have mild symptoms, while others are severely affected and have difficulty participating in everyday life with neurotypical people.
What have recent advances been?
In the past 50 years since ASD has been researched, many new technological and scientific advances have been made. New technology in genetics is a major advancement. Techniques that are standard in genetics today did not exist 50 years ago. These include karyotyping, fluorescence in situ hybridization, chromosome misarray technology, whole-genome and whole-exome sequencing.
What is a biomarker?
A biomarker is a biological measure, most often a gene, that signals the presence of a disease or disorder. Physicians and scientists find biomarkers helpful to diagnose the disease or disorder early, to predict the course or prognosis, identify risk factors, identify the best treatment. Researchers particularly hope that genetics may help them identify the relationship between autism and intellectual disability. Some people with ASD also have intellectual disability while others do not.
Finding a biomarker in autism is particularly difficult. One difficulty is that autism is a spectrum disorder that encompasses many different symptoms. It encompasses disorders that used to be separated, like Asperger, Rett, childhood disintegrative disorder, and pervasive developmental disorder. The symptoms of ASD vary individually. Finding one biomarker, or even a group of biomarkers, that is related to such a wide variety of symptoms is difficult.
What are the genetic findings?
As stated above, the genetic findings of variants related to autism are complicated. Scientists have discovered hundreds of genetic changes, including changes in individual base pairs called single-nucleotide variants (SNVs). They have also discovered thousands to millions of base pair changes, called copy number variants (CNV). While these changes are inherited, they have also discovered de novo variants. De novo variants mean that the DNA in the child has spontaneously developed this mutation rather than inherit it from either parent. Specifically, many of these de novo mutations cause that gene to lose its original function. This is called a loss-of-function mutation.
There are certain genetic mutations that cause syndromes that are associated with autism. These conditions include Rett syndrome, Fragile X, tuberous sclerosis, and PTEN mutations. However, people with these syndromes do not always express autism-like symptoms. When they do, they are associated with intellectual disability. Scientists are still researching why only some patients with these syndromes are affected by autism. This issue is described by the
scientific words “penetrance” and “expressivity”. Researchers are still puzzled as to why some people with the same genetic variants have a different severity of autism while others may have minimal symptoms.
Because many of these genetic variants are associated with medical conditions like those mentioned above, some scientists believe that the other genetic variants may be biomarkers of medical conditions that have otherwise never been genetically marked before. While this is just a theory, it is interesting to consider nonetheless.
What treatment options are available to target these causes?
With these findings, scientists believe that these genetic variants account for 10-30% of people with ASD today. One major reason that researchers want to study the genetics of autism is that ASD is often found in conjunction with other disorders. Using genetics, they can find and target these comorbidities. Additionally, there is a growing belief that targeting pharmacotherapy to genetic variants is the next frontier in pharmacotherapy. This means that people with certain genetic variants are better treated with one medication over another. Additionally, scientists believe that behavioral treatments of autism can be targeted based on the genetic variant.
Conclusion
ASD is a term used to describe many different symptoms that inhibit how people interact socially and emotionally. Science has long been studying this disorder, and new technologies and discoveries have brought about new insight into the field. These include new genetic advances that can shape how the disorder is treated.
