Gene Expression Profile Identifies Autistic Infants and Toddlers

A team of neuroscientists has developed a prototype blood-based assay that is able to differentiate children with normal development from those with autism when they are as young as one to two years.

The identification of genomic signatures that are able to aid early identification of individuals at risk for autism spectrum disorder (ASD) in the toddler period remains a major challenge because of the genetic and phenotypic heterogeneity of the disorder. Generally, ASD is not diagnosed before the fourth to fifth birthday.

Investigators at the University of California, San Diego (USA) turned to genomic analysis technology to establish a quantitative assay that could confirm the presence of ASD at a much earlier stage of development. They determined gene expression profiles from blood samples taken from two independent cohorts of male infants and toddlers aged one to four years (142 discovery participants and 73 replication participants) by using Illumina (San Diego, CA, USA) DNA microarrays to measure leukocyte RNA expression levels.

Results revealed that the assay correctly identified the patients with ASD in the first group (91 known to have ASD, 56 controls) 83% of the time and in the second group (44 known to have ASD, 29 controls) 75% of the time. The assay did not differentiate normally developing toddlers from non-autistic children with global developmental or language delay problems.

"A major challenge is the difficulty of accurately diagnosing ASD, which is very heterogeneous, at an early enough age to implement the most effective treatment," said senior author Dr. Eric Courchesne, professor of neurosciences at the University of California, San Diego. "Our present study shows examination of the gene expression profiles at the very early age of initial clinical detection reveals both strong evidence of early biological processes in ASD and abnormal signals with the potential to serve as an early, practical biomarker of risk for the disorder in general pediatric settings."

"Ideally, biomarkers come from tissue affected, but in ASD this is the brain, which is obviously an inaccessible tissue," said Dr. Courchesne. "Peripheral blood of living ASD infants and toddlers is an important alternative, and obtaining blood samples is routine and safe and, thus, is a preferable and accessible tissue for identifying signatures of ASD that could be used in clinical screening and follow-up evaluations."

The study was published in the March 4, 2015, online edition of the journal JAMA Psychiatry.

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