Thursday, April 23, 2015

Study Links Autism to Epigenetic Changes in Dads' Sperm

Researchers have found tell-tale “epigenetic” changes in the DNA from the sperm of men whose children have early signs of autism. These changes – which are likely passed on to offspring – may reflect, in part, the men’s exposure to environmental hazards. Epigenetics and environmental risk factors for autism A growing body of research has suggested that environmental influences – including infection and exposure to toxic chemicals – can produce epigenetic changes in the cells that make sperm and eggs. Sperm-making cells may be particularly vulnerable to such environmental exposures. Many experts believe that this explains why autism rates are significantly higher among the children of older dads. Their germ cells have been exposed to more environmental “hits” over the course of a lifetime. In their new study, the Johns Hopkins investigators analyzed the epigenetic markers on DNA in the sperm from 44 dads. The men were part of the ongoing Early Autism Risk Longitudinal Investigation (EARLI). EARLI enrolls families that have a child with autism and follows them through subsequent pregnancies and the birth and development of younger siblings. Early in their wives’ pregnancies, the men provided sperm samples for DNA and epigenetic analysis. One year after birth, the younger siblings were assessed for early signs of autism. The researchers then looked at the likelihood that a child’s autism symptoms corresponded to an epigenetic change at a particular site in a father’s sperm DNA. They found 193 such sites. At each of these sites, epigenetic changes were significantly associated with children’s autism symptoms. When the researchers looked at which genes were near the “high risk” sites, they found that many are in or near genes crucial to brain development. In a related analysis, the investigators found several of the tell-tale epigenetic changes in the post-mortem brain tissue of individuals with autism – providing further evidence that these changes may predispose to autism.

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