Summary: According to researchers, children with ASD have more harmful mitochondrial mutations than their family members.
Study of 903 affected children shows inherited, spontaneous mutations increase risk.
Children diagnosed with autism spectrum disorder (ASD) have greater numbers of harmful mutations in their mitochondrial DNA than family members, report Zhenglong Gu of Cornell University in Ithaca, New York, and colleagues, in a study published October 28th, 2016 in PLOS Genetics.
Increasingly, studies [1,2] point to malfunctions in mitochondria – the powerhouses of the cell – as a cause of autism spectrum disorder, but the biological basis for this relationship is unclear. To see if a genetic link exists between mitochondrial malfunction and ASD, the scientists analyzed mitochondrial DNA sequences from 903 children with ASD, along with their unaffected siblings and mothers. They discovered a unique pattern of heteroplasmic mutations, where both mutant and normal mitochondrial DNA sequences exist in a single cell. Children with ASD had more than twice as many potentially harmful mutations compared to unaffected siblings, and 1.5 times as many mutations that would alter the resulting protein. The researchers went on to show that these mutations can be inherited from the mother, or the result of spontaneous mutation during development.
The scientists noted that the risk associated with these mutations is most pronounced in children with lower IQ and poor social behavior compared to their unaffected siblings. Carrying harmful mutations in mitochondrial DNA is also associated with increased risk of neurological and developmental problems among children with ASD. Because mitochondria play a central role in metabolism, these findings may help explain the metabolic disorders commonly associated with ASD and other neurodevelopmental disorders. Evaluating mutations in the mitochondrial DNA of high-risk families could help improve the diagnosis and treatment of these diseases.
Zhenglong Gu says “The result of our study synergizes with recent work on ASD, calling attention to children diagnosed with ASD who have one or more developmental abnormalities or related co-morbid clinical conditions for further testing on mitochondrial DNA and mitochondrial function. Since many neurodevelopmental disorders and related childhood disorders show abnormalities that converge upon mitochondrial dysfunction, and may have mtDNA defects as a common harbinger, future research is needed to elucidate the mitochondrial mechanisms underpinning to these diseases. Ultimately, understanding the energetic aspects of neurodevelopmental disorders may lead to entirely new kinds of treatments, and preventative strategies that would target mitochondria.”
About this autismresearch article
Funding: This work was supported by various funds from Cornell University, NSF MCB-1243588, NIH 1R01AI085286, and a grant for ENN science and technology development to ZG. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
Source: Zhenglong Gu – PLOS Image Source: NeuroscienceNews.com image is credited to Darryl Leja, NHGRI, Flickr. Original Research: Full open access research for “Genetic Evidence for Elevated Pathogenicity of Mitochondrial DNA Heteroplasmy in Autism Spectrum Disorder” by Yiqin Wang, Martin Picard, and Zhenglong Gu in PLOS Genetics. Published online October 28 2016 doi:10.1371/journal.pgen.1006391
Cite This NeuroscienceNews.com Article
[cbtabs][cbtab title=”MLA”]PLOS. “Autism Spectrum Disorder Linked to Mutations in Some Mitochondria.” NeuroscienceNews. NeuroscienceNews, 28 October 2016. <https://neurosciencenews.com/asd-mitochondria-psychology-5379/>.[/cbtab][cbtab title=”APA”]PLOS. (2016, October 28). Autism Spectrum Disorder Linked to Mutations in Some Mitochondria. NeuroscienceNews. Retrieved October 28, 2016 from https://neurosciencenews.com/asd-mitochondria-psychology-5379/[/cbtab][cbtab title=”Chicago”]PLOS. “Autism Spectrum Disorder Linked to Mutations in Some Mitochondria.” https://neurosciencenews.com/asd-mitochondria-psychology-5379/ (accessed October 28, 2016).[/cbtab][/cbtabs]
Genetic Evidence for Elevated Pathogenicity of Mitochondrial DNA Heteroplasmy in Autism Spectrum Disorder
Increasing clinical and biochemical evidence implicate mitochondrial dysfunction in the pathophysiology of Autism Spectrum Disorder (ASD), but little is known about the biological basis for this connection. A possible cause of ASD is the genetic variation in the mitochondrial DNA (mtDNA) sequence, which has yet to be thoroughly investigated in large genomic studies of ASD. Here we evaluated mtDNA variation, including the mixture of different mtDNA molecules in the same individual (i.e., heteroplasmy), using whole-exome sequencing data from mother-proband-sibling trios from simplex families (n = 903) where only one child is affected by ASD. We found that heteroplasmic mutations in autistic probands were enriched at non-polymorphic mtDNA sites (P = 0.0015), which were more likely to confer deleterious effects than heteroplasmies at polymorphic mtDNA sites. Accordingly, we observed a ~1.5-fold enrichment of nonsynonymous mutations (P = 0.0028) as well as a ~2.2-fold enrichment of predicted pathogenic mutations (P = 0.0016) in autistic probands compared to their non-autistic siblings. Both nonsynonymous and predicted pathogenic mutations private to probands conferred increased risk of ASD (Odds Ratio, OR[95% CI] = 1.87[1.14–3.11] and 2.55[1.26–5.51], respectively), and their influence on ASD was most pronounced in families with probands showing diminished IQ and/or impaired social behavior compared to their non-autistic siblings. We also showed that the genetic transmission pattern of mtDNA heteroplasmies with high pathogenic potential differed between mother-autistic proband pairs and mother-sibling pairs, implicating developmental and possibly in utero contributions. Taken together, our genetic findings substantiate pathogenic mtDNA mutations as a potential cause for ASD and synergize with recent work calling attention to their unique metabolic phenotypes for diagnosis and treatment of children with ASD.
“Genetic Evidence for Elevated Pathogenicity of Mitochondrial DNA Heteroplasmy in Autism Spectrum Disorder” by Yiqin Wang, Martin Picard, and Zhenglong Gu in PLOS Genetics. Published online October 28 2016 doi:10.1371/journal.pgen.1006391