Mitochondrial Genetic Patterns Associated With Autism

Scientists have suggested that alterations in the mitochondrial DNA that were determined by human migrations may be associated with the risk of suffering from autism. Their research was published in JAMA Psychiatry. Mitochondria are tiny organelles that are present in every cell of our body. They are known as the power houses of the body. They generate energy from the nutrition that is supplied to the cells by the blood, which is utilized for the functioning of the body. Mitochondria also play a role in several other functions which include the synthesis of the genetic material DNA and RNA, hemoglobin, estrogen and testosterone, and the breaking down of cholesterol and detoxification.

Though most of the cellular DNA is located within the nucleus, mitochondria have their own DNA, which is solely inherited from the mother. Depending on the mutations that took place over time, the mitochondrial group of genes have been classified into haplogroups. Haplogroups consist of a group of genes that are inherited together from a single parent and reflect the line of descent. Depending on the human migration, different haplogroups moved to different parts of the world. The mitochondrial haplogroups thus reflect the ancient migration patterns out of Africa into the rest of the world.

The scientists suggest that the genetic variations in the mitochondria may play a role in the development of autism spectrum disorders (ASD). Autism spectrum disorders are a group of development disorders in which the patients suffer from difficulty with communication and social interaction along with repetitive or restrictive behavior. Patients have focused but long-lasting interests in certain topics. They have a problem with conversations but can talk at length on their topic of interest. They get upset if their routines or settings are suddenly changed. They, however, usually have above average intelligence and may even excel in the fields of mathematics, art, music and science. Genetic and environmental factors have been implicated in increasing the risk of suffering from ASD. Medications may be used to control symptoms of irritability, aggression, anxiety, depression, hyperactivity and attention problems to some extent.

The scientists obtained the genetic data for their study from the Autism Genetic Resource Exchange (AGRE). The study was conducted on the data obtained from 1,624 patients and 2,417 healthy parents and siblings from 933 families.

The scientists found that Europeans with the haplogroups I, J, K, X, T and U had a higher risk of ASD as compared to those with HHV, which is the most common European haplogroup. The risk was also higher in those with the Asian and Native American haplogroups A and M.

The increased risk for ASD has a possible explanation. The variations in the mitochondria can affect the brain and cause an imbalance between the excitation and inhibition of brain activity thereby predisposing to ASD.

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ASD is more common in males as compared to females, similar to other mitochondrial diseases like Leber hereditary optic neuropathy (LHON). This fact also increases the possibility of it being linked to a mitochondrial disorder.

Taking the findings of the study further, the scientists suggest that metabolic treatments could be developed and evaluated in the future for their possible benefits in this group of patients.

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Reference:

1. Autism Spectrum Disorder - (https://www.nimh.nih.gov/health/topics/autism-spectrum-disorders-asd/index.shtml)
2. "Association between Mitochondrial DNA Haplogroup Variation and Autism Spectrum Disorders," JAMA Psychiatry, online Aug. 23, (2017). http://doi.org/10.1001/jamapsychiatry.2017.2604

Source-Medindia