Researchers Are Working to Pinpoint Genetic Causes of Autism

Distinct genetic influences among people all along the autism spectrum were observed based on data provided by SPARK (the largest autism cohort), according to a series of articles published in Nature Genetics lately, uncovering the truth that despite the known genes associated with autism are responsible for most de novo variants, others are yet to be identified.

Challenging Behaviors of Autism

Autism, or autism spectrum disorder (ASD), is one of the most prevalent neurodevelopmental disorders, affecting an estimated 1 in 44 children in the US according to CDC. People with ASD usually face obstacles with social skills, repetitive behaviors, speech, and nonverbal communication. However, each of them has a distinct set of strengths and challenges, which means the ways they learn, think and problem-solve may vary greatly. Although most of them may show signs of cognitive differences or epilepsy, some extremely talented and exceptional individuals in specific areas are frequently observed.

ASD is highly genetically heterogeneous and may be caused by both inheritable and de novo gene variations. Hundreds of genes have been identified so far to contribute to the serious deficits in communication, social cognition, and behavior that patients often experience. However, this only accounts for no more than 20% of ASD cases, and patients with similar pathogenic variants may be diagnosed on very different levels of the spectrum. Hence, the focus of scientists now could be concluded into three main points: how genetic factors contribute to different phenotypes vary in terms of the genes involved, when those genes are activated during brain development, and how common some of the genetic variants are in the population.

Related article: The Brain Size Changes with Age: A First Worldwide Brain Study

How Does Autism Link to Genetic Variation?

In the study published on 18 Aug, researchers from Columbia University Medical Center analyzed the DNA of more than 42,600 people with ASD, including 35,000 participants from the SPARK autism research study. By including 16,877 participants with ASD, along with one or both of their biological parents, the researchers found out that approximately 20% of people with ASD have de novo genetic variants that affect the function of the associated gene. Nearly 70% of this genetic contribution can be attributed to known autism or neurodevelopmental disorder genes. 

Results of meta-analysis after the addition of 22,764 individuals with autism and 236,000 people without ASD from the general population identified 60 autism genes whose contribution to autism is largely driven by the rare inherited loss of function (LoF) variants transmitted by parents who show no cognitive differences or autism. Five among all of them identified have not previously been implicated in neurodevelopmental conditions.

In another study led by Michael E. Talkowski, Ph.D. The Director of the Center for Genomic Medicine (CGM) at MGH, also states that rare coding variation provides insight into the genetic architecture and phenotypic context of autism, after analysis of genetic data from 20,627 people with ASD.

With the newly developed scientific approach, the team discovered gains and losses of DNA, or copy number variants (CNVs), from exome sequencing and strategies to integrate data from these CNVs with other classes of de novo and rare inherited variants identified 72 genes associated with autism. The researchers then combined data from the autism studies with a large dataset of 31,000 families in which the child was diagnosed with neurodevelopmental conditions and successfully discovered 373 genes associated with these diverse neurodevelopmental outcomes. The result allowed the team to identify genes more associated with ASD than other neurodevelopmental conditions and vice versa. 

To sum up, these recent studies provide new insights into the genetic nature of autism, although the exact pathway remains unknown, these new studies will inspire different ideas to improve understanding of autism.

Author

Nai Ye Yeat

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