Genome’s ‘dark’ side steps into spotlight of autism research

from SpectrumNews by Nicholette Zeliadt – Given that genes make up a paltry 2 percent of the genome, they’ve received a disproportionate amount of attention from autism researchers. Slowly, however, the other 98 percent of the genome — the so-called ‘dark matter’ — is emerging from the shadows.

Once considered nonfunctional or ‘junk DNA,’ these non-gene regions are now known to contain instructions for making pieces of RNA that fine-tune the activity of genes. The RNA segments control when and where genes are active. Autism researchers have looked at the role of these RNAs for only about a decade, but they already have tantalizing clues that the segments seem to be involved in the condition.

“It’s an important field that hasn’t really been studied very much yet,” says Daniel Campbell, assistant professor of psychiatry at the University of Southern California in Los Angeles.

Evidence so far suggests that some noncoding RNAs are unusually scarce and others unusually abundant in people with autism. A few of the RNAs regulate autism genes or signaling pathways implicated in the condition.

Because of this, noncoding RNAs could also lead to treatments for autism.

“When the cause of a disorder is in the regulation of genes, then it might be a better target for intervention than having to repair a gene,” says Dorret Boomsma, professor of genetics and psychology at Vrije University in Amsterdam.

The long and short of it:

There are two major types of noncoding RNA: short stretches called microRNAs, which are roughly 20 nucleotides in length; and so-called long noncoding RNAs (lncRNAs), which have more than 200 nucleotides.

Both types typically turn genes off, but do so in different ways. microRNAs bind to messenger RNA (mRNA), the template for a protein that’s created from a gene, and either destabilize it or block the machinery that translates it into protein. lncRNAs target mRNAs, but they can also bind and block microRNAs. And they can influence gene expression — by interacting either with proteins that turn genes on or off or with those that control how tightly DNA is packed in the nucleus.  (read more…)

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