Glowing neurons

Luminescence helps scientists study the work of individual neurons in the animal brain

marks, Geektimes

Species of living organisms capable of luminescence are not so rare. These are fireflies, bacteria, and jellyfish with worms, not to mention deep-sea fish and other animals. Luminescence helps these organisms attract prey, communicate, or simply illuminate the space next to them. A team of scientists from Vanderbilt University managed to put luminescence at their service. Scientists have obtained a genetically modified form of an enzyme that causes bioluminescence of body cells and with its help "taught" brain cells to glow.

The aim of the project is to provide bioluminescence of brain neurons during their operation. This, according to scientists, allows us to better understand the principle of the brain of simple organisms, which can lead to an understanding of the principles of the brain of more complexly organized animals.

Modern scientists already have at their disposal technologies for tracking individual neurons of the brain. But these technologies have a number of limitations. For example, they can be used to monitor the work of only a certain number of neurons. And there are more than 86 billion of them in the human brain, so existing electrophysiological methods do not allow monitoring the work of all departments of this complex organ at the same time. Perhaps modified luciferase will help solve this problem in the near future.

The team of researchers published the results of their work in the publication Nature Communications (Yang et al., Coupling optogenetic stimulation with NanoLuc-based luminescence (BRET) Ca++ sensing). The basis is the previous research results of specialists in the field of luminescence (the team previously studied the unicellular algae chlamydomonas) and optogenetics.

Optogenetics is a technique for studying the work of nerve cells, which is based on the introduction of special channels into their membrane – opsins that react to light excitation. Genetic engineering methods are used to express channels. Lasers, optical fiber and other sophisticated optical equipment are used to activate or suspend the activity of neurons and their networks. Optogenetics appeared in 2005. Then scientists for the first time used such an opsin as channelrhodopsin-2 (channelrhodopsin-2, ChR2).

Optogenetics allows not only to cover a larger number of neurons in observation than in the case of working with electrophysiological methods for studying neural networks. It also opens up the possibility of highly selective activation or suppression of certain neuronal connections. Experts say that this will help to carry out effective therapy for Parkinson's disease, depression, anxiety and epilepsy. In the case of optogenetics methods, scientists usually work with fluorescence.

According to Professor of Biology Karl H. Johnson (Carl H. Johnson), who heads the study, bioluminescence should be used instead of fluorescence. "The light that is generated by the fluorescent cells is suppressed by the illumination necessary for observation. Luminescence works in the dark," the scientist said. The problem is also that it is not so easy to introduce fluorescent material into all parts of the brain of interest to scientists, given the need to introduce it into each individual neuron.

Therefore, scientists have found a different approach. They took luciferase from the body of a luminescent shrimp species, and genetically modified it in such a way that the light activity of luciferase began to manifest in the presence of calcium molecules. The concentration of calcium is quite high in neurons, but, at the same time, this element is not enough outside the brain cells. When the neuron receives a signal, the concentration of calcium becomes maximum, which leads to the luminescence of the involved cell. The modified enzyme was able to attach to brain cells thanks to the virus. With its help, scientists have introduced an enzyme into the calcium sensor, introducing it into the neuron.

Luminescence of individual neurons has become possible
thanks to the use of a genetically modified enzyme

So far, the new technology is being tested on neurons grown in the laboratory, as well as on slices of the hippocampus of the brain of mice. It takes three weeks to prepare a luminescent sample. In both cases, the neurons began to luminesce when receiving an electrical signal, leading to an increase in the concentration of calcium. The success of scientists is also due to the fact that a new luciferase, called NanoLuc, has recently been created.

"We have shown that our technology works," Johnson said. "Now we need to determine how sensitive she is. We believe that the new method is accurate enough to determine the activation of individual neurons, but in order to verify this, we need to conduct additional tests."

The researchers posted information about the genetically modified enzyme on the AddGene resource. Access to this information is free.

Portal "Eternal youth" http://vechnayamolodost.ru  01.11.2016