Children diagnosed with autism spectrum disorder (ASD) have greater numbers of harmful mutations in their mitochondrial DNA (mDNA) than family members, US researchers have found.Autism is a serious developmental disorder that impairs the ability to communicate and interact.Previous studies pointed out to the malfunctions in mitochondria -- the powerhouse of the cell -- as a major cause of ASD, however, the biological link was not established. In the new study, the researchers discovered a unique pattern of heteroplasmic mutations, where both mutant and normal mDNA sequences exist in a single cell.Children with ASD have 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 result of our study synergises 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 mDNA and mitochondrial function," said Zhenglong Gu of Cornell University in Ithaca, New York.
Further, the study showed that these mutations can be inherited from the mother, or could be a result of spontaneous mutation during development.Carrying harmful mutations in mDNA is also associated with increased risk of neurological and developmental problems among children with ASD, because mitochondria plays a central role in metabolism.The risks are most pronounced in children with lower IQ and poor social behaviour compared to their unaffected siblings, the researchers said. "Since many neurodevelopmental disorders and related childhood disorders show abnormalities that converge upon mitochondrial dysfunction, and may have mDNA defects as a common harbinger, future research is needed...," Gu noted.For the study, published in the journal PLOS Genetics, the scientists analysed mDNA sequences from 903 children with ASD, along with their unaffected siblings and mothers.