According to the latest statistics from the U.S. Centers for Disease Control and Prevention (CDC), nowadays one in 50 children in the United States are diagnosed with autism. To compare, these numbers were much lower in the 1980s, when only one in 5,000 were diagnosed with an autism spectrum disorder (ASD). This disease turns into a real epidemic and everyday researchers get a step closer to the factors that cause autism.
A recent study published on October 6th in Cell, shows that mutations in stretches of the genome may play a role in autism. Most of these “human accelerated regions” (HARs) do not code for proteins, but may control genes required for brain development. However, some experts are skeptical of this theory.
The researchers analyzed mutations in 2,100 children with autism and their healthy siblings from ‘simplex’ families, in which only one child has autism. They were looking for the large duplications or deletions in DNA – copy number variations (CNVs) — that include HARs. The scientists found that spontaneous, or non-inherited, CNVs occur 6.5 times more often in people with autism than in their siblings.
Though, the researchers say that all but two of these CNVs also overlap with parts of the genome that code for proteins. This makes it difficult to analyze how much the HARs alone increase risk of autism. Mutations in HARs underlie up to 5% of autism cases in the consanguineous families in the study, the researchers say. They also characterized three of the mutations that occur next to or within genes involved in brain development. One of these genes, CUX1, regulates the number of neuronal junctions, or synapses.
Unfortunately, it is still unclear if HARs are important in non-consanguineous families and increase the risk of autism. Probably, researchers need to increase the number of families to see it.