Biomarkers in human sperm have been found to indicate a propensity to autism spectrum disorder in the fathers’ offspring.
Autism spectrum disorder
Autism spectrum disorder (ASD) is a complex neurological disorder involving deficits in communication, social behaviours and stereotypic movements. There has been an increase in prevalence of ASD over the last two decades. For example, prevalence of ASD in 1975 was reported as 1 in 5,000. Whereas the prevalence in 2014 was 1 in 68. It is thought that this increase is due to environmental and molecular factors.
Genetic studies using GWAS have identified several genetic variants, yet these variants only account for a small percentage. Nonetheless, a recent study has shown that combining genetic mutations and altered epigenetics appears to improve associations. While experts anticipate genetics to be a component of ASD aetiology, it is now thought that environmental epigenetics also plays an important factor.
Although both parents can transmit ASD, paternal transmission appears to be higher in most population. One of the main factors suggested is paternal age. Specifically, increased paternal age has been associated with epigenetic DNA methylation alterations in sperm.
In a study, published in Clinical Epigenetics, researchers aimed to identify a DNA methylation signature in sperm to use as a potential biomarker to identify paternal offspring autism susceptibility. Sperm samples were obtained from fathers with and without children with autism. The sperm was then assessed for alterations in DNA methylation, specifically a genome-wide analysis for differential DNA methylation regions (DMRs).
The team identified 805 DMR genomics features, such as chromosomal location, CpG density and length of DMRs, that could be used as an epigenetic biomarker for susceptibility. They tested their findings by attempting to identify fathers with and without autistic children based on their sperm samples alone. The team correctly identified all fathers, except for two false negatives – an accuracy rate of ~90%.
More work needs to be done in order to develop the team’s findings into a potential clinical tool. In addition, with further research, this tool could be used to identify what types of environmental factors may induce these types of epigenetic changes.
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