New live imaging technique shows how brain works

For the first time, scientists have been able to observe intact interactions between proteins directly in the brain of a live animal.
The new live imaging approach was developed by a team of researchers at the University of Miami (UM).
"Our ultimate goal is to create the systematic survey of protein interactions in the brain," said Akira Chiba, professor of Biology in the College of Arts and Sciences at UM and lead investigator of the project.
The new technique will allow scientists to visualise the interactions of proteins in the brain of an animal, along different points throughout its development, said Chiba.

"We know that proteins are one billionth of a human in size. Nevertheless, proteins make networks and interact with each other, like social networking humans do," Chiba said.
"The scale is very different, but it's the same behaviour happening among the basic units of a given network," Chiba said.

The researchers chose embryos of the fruit fly (Drosophila melanogaster) as an ideal model for the study. Because of its compact and transparent body, it is possible to visualise processes inside the Drosophila cells using a fluorescence lifetime imaging microscope (FLIM).
The results of the observations are applicable to other animal brains, including the human brain.

The Drosophila embryos in the study contained a pair of fluorescent labelled proteins: a developmentally essential and ubiquitously present protein called Rho GTPase Cdc42 (cell division control protein 42), labelled with green fluorescent tag and its alleged signalling partner, the regulatory protein WASp (Wiskot-Aldrich Syndrome protein), labelled with red fluorescent tag.
Together, these specialised proteins are believed to help neurons grow during brain development. The proteins were selected because the same (homolog) proteins exist in the human brain as well.
Previous methods required chemical or physical treatments that most likely disturb or even kill the cells. That made it impossible to study the protein interactions in their natural environment.

The current study addresses these challenges by using the occurrence of a phenomenon called Forster resonance energy transfer, or FRET.
It occurs when two small proteins come within a very small distance of each other, (eight nanometres). The event is interpreted as the time and place where the particular protein interaction occurs within the living animal.
The findings show that FRET between the two interacting protein partners occurs within neurons, during the time and space that coincides with the formation of new synapses in the brain of the baby insect.