Stretches of DNA that move around the brain, colloquially known as jumping genes, may play a role in fostering one pernicious form of autism. It has long been known that a a mutation that switches off a gene called MECP2 is involved in Rett syndrome, the most physically disabling form of autism. Rett, which mostly affects girls, results in speech and motor defects that appear just after children learn to speak their first words and start walking.

In the Nov. 18, 2010, Nature, Alyson Muotri, Fred Gage and Carol Marchetto found that jumping genes, more formally known as LINE-1 retrotransposons, may help explain why a single mutation may cause a diverse panoply of symptoms. When the mutation disables the gene, it causes the jumping genetic elements to move around human stem cells six times more than they do in normal (wild type) cells. The hyperkinetic activity of the jumping genes may act as “promoters” that turn on genes inside a brain cell and then lead to some of the symptoms of the neurodevelopmental disorder.

This animation  by Muotri and Marchetto shows the higher rate of activity of the jumping genes in the Rett-afflicted cells (more green dots) than in the WT (wild type) ones. (The olfactory bulb is shown in red, the striatum in magenta and the cerebellum in cyan.) The importance of jumping genes in health and disease is detailed in the March issue of Scientific American­­­–an article entitled “What Makes Each Brain Unique.”

Source: Carol Marchetto and Alysson Muotri with permission from Nature

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