Mutations in genes can cause devastating effects on the neurological system. Using fruit flies, researchers have shown for the first time how a DNA mutation can have a positive influence on human intelligence—namely, a higher IQ in humans.
Synapses are the locations in the brain where nerve cells communicate with one another. Because changed synaptic proteins, for example, might hamper this complicated chemical pathway, disruptions in this communication lead to nervous system illnesses. This can cause modest symptoms as well as serious disability in those who are affected.
Professor Tobias Langenhan and Professor Manfred Heckmann of Leipzig and Würzburg, respectively, became interested in a mutation that damages a synaptic protein after reading about it in a scientific journal. The affected patients initially drew investigators’ notice since the disease rendered them blind. Doctors later discovered that the patients were also intellectually above average.
According to the authors, “it’s very rare for a mutation to lead to improvement rather than loss of function.”
For many years, two neurobiologists from Leipzig and Würzburg have used fruit flies to study synaptic activities.
This “project was designed to insert the patients’ mutation into the corresponding gene in the fly and use techniques such as electrophysiology to test what then happens to the synapses,” says Langenhan, adding, “It was our assumption that the mutation makes patients so clever because it improves communication between the neurons which involve the injured protein. Of course, you can’t conduct these measurements on the synapses in the brains of human patients. You have to use animal models for that.”
First, the scientists demonstrated that the fly protein RIM is molecularly identical to that of humans, in collaboration with Oxford academics. This was necessary in order to observe changes in the human brain on the fly. The neurobiologists then implanted mutations into the fly genome that were identical to those found in ill individuals. They then measured synaptic activity electrophysiologically.
They found “that the animals with the mutation showed a much increased transmission of information at the synapses. This amazing effect on the fly synapses is probably found in the same or a similar way in human patients, and could explain their increased cognitive performance, but also their blindness.”
The scientists also discovered how greater transmission at synapses occurs: the mutation effect causes the chemical components in the transmitting nerve cell that trigger synaptic impulses to shift closer together, resulting in a higher release of neurotransmitters.
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