Tiny, poorly understood gene fragments are linked to altered brain development in autism, according to new research from scientists at the University of Toronto.

Their study, published in the journal Cell, focuses on small segments called microexons. Microexons are tiny stretches of DNA that code for equally tiny parts of proteins.

Until now, only a handful of these extra-short microexons were known. The Cell paper identifies hundreds of new ones.

Moreover, microexons appear to have been underestimated. The scientists found that the vast majority of microexons form parts of genetic messages that are expressed in neurons in the brain, and that they play an important role in how those neurons function. When the scientists deleted microexons in the lab, proteins in the neurons had trouble interacting with each other.

They also analyzed samples of brain tissues from individuals with autism spectrum disorder, and found many microexons were missing in the genetic messages.

The research was noted in two separate scientific editorials Thursday as a major step forward. It involved an international team of researchers and was led by Manuel Irimia, a post-doctoral fellow, and Benjamin Blencowe, a professor, at the Donnelly Centre for Cellular and Biomolecular Research. (Blencowe is also a co-author on Fridays machine-learning study in Science.)

What weve done is to perform a more systematic search for these microexons, using a massive amount of data, says Blencowe. But what was really missing from the picture before . . . is that these microexons are regulated in a really specific manner, and that they are detected primarily in the nervous system.

The team also found that the microexons are highly conserved, meaning they havent evolved very differently in humans and other animals like mice, suggesting they play a basic, central role in development.

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Tiny gene fragments linked to altered brain development in autism, U of T scientists say

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