Autism spectrum disorder (ASD) may result from mild defects in the mitochondria of brain cells, early research in mice has shown.
So far, hundreds of genetic mutations have been associated with ASD, however scientists are still missing a consensus as to how they cause the condition. According to the researchers at Children's Hospital of Philadelphia, a proportion of ASD cases could be caused by mild genetic changes in the mitochondria and may be treated by metabolic therapies in the future.
'Our study shows that mild systemic mitochondrial defects can result in autism spectrum disorder without causing apparent neuroanatomical defects,' said Dr Douglas Wallace, senior co-author of the publication. 'These mutations appear to cause tissue-specific brain defects. While our findings warrant further study, there is reason to believe that this could lead to better diagnosis of autism and potentially treatments directed toward mitochondrial function.'
Mitochondria produce most of the body's energy and therefore are known as the 'batteries' of the cell. As previous studies had shown an association between variants of mitochondrial DNA (mtDNA) and ASD, the investigators suggested that a mouse model with the same relevant mtDNA mutations should present with autism endophenotypes. These are described measurable traits commonly experienced by ASD patients and included behavioural, neurophysiological, and biochemical features.
Dr Wallace commented: 'Autism spectrum disorder is highly genetically heterogeneous, and many of the previously identified copy number and loss of function variants could have an impact on the mitochondria.'
The study, published in the Proceedings of the National Academy of Sciences, revealed that mice modified with a mild missense mutation in the mtDNA ND6 gene exhibited common features associated with ASD: impaired social interactions, increased repetitive behaviours and anxiety. Furthermore, the scientists reported aberrations in electroencephalograms, more seizures, and brain-region specific defects on mitochondrial function. Nevertheless, there was no obvious change in the brain's anatomy, suggesting that the mitochondrial energetic defects alone may have been sufficient to cause autism endophenotypes.
'Autism spectrum disorder has a prevalence in the United States among eight-year-old children of one in 54 with the incidence in males being one in 34 and females one in 145,' the authors wrote. They conclude that with their findings, at least some ASD patients could hope for metabolic therapies as a potential treatment strategy in the future.