Abstract
We review the current status of the role and function of the mitochondrial DNA (mtDNA) in the etiology of autism spectrum disorders (ASD) and the interaction of nuclear and mitochondrial genes. High lactate levels reported in about one in five children with ASD may indicate involvement of the mitochondria in energy metabolism and brain development. Mitochondrial disturbances include depletion, decreased quantity or mutations of mtDNA producing defects in biochemical reactions within the mitochondria. A subset of individuals with ASD manifests copy number variation or small DNA deletions/duplications, but fewer than 20 percent are diagnosed with a single gene condition such as fragile X syndrome. The remaining individuals with ASD have chromosomal abnormalities (e.g., 15q11-q13 duplications), other genetic or multigenic causes or epigenetic defects. Next generation DNA sequencing techniques will enable better characterization of genetic and molecular anomalies in ASD, including defects in the mitochondrial genome particularly in younger children.
Highlights
We review the current status of the role and function of the mitochondrial DNA in the etiology of autism spectrum disorders (ASD) and the interaction of nuclear and mitochondrial genes
Rating scales helpful in establishing the diagnosis are Autism Diagnostic Interview- Revised (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS) in combination with clinical presentation [5, 6]
An autism genome-wide copy number variation study reported by Glessner et al [25] in a large cohort of Autism Spectrum Disorders (ASD) cases compared with controls showed that NRXN1 and CNTN4 genes play a role
Summary
The etiology of ASD is complex and encompasses the roles of genes, the environment (epigenetics) and the mitochondria. An autism genome-wide copy number variation study reported by Glessner et al [25] in a large cohort of ASD cases compared with controls showed that NRXN1 and CNTN4 genes play a role. They described new susceptibility genes, NLGN1 and ASTN2 which encode neuronal cell-adhesion molecules and other genes involved in the ubiquitin pathways (UBE3A, PARK2, RFWD2 and FBXO40), two important gene networks expressed in the central nervous system. Medical intervention and therapies are available to target the biochemical defect in the mitochondria and to improve function and bioenergy utilization and diminish the neurological insults that would occur if left untreated
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