A Glowing Protein Shows How We Make Memories

A new strain of genetically engineered mice has allowed researchers to pinpoint, for the first time, the precise cellular connections that form as a memory is created. By tracing a protein tagged to glow fluorescent green as it migrates through individual neurons, from the cell body out through the branching dendrites, the researchers could see exactly which synapses–connections to other neurons–were involved when the mice learned to fear an electric shock.

 Making Memories


Follow the glow: By engineering mice to manufacture a fluorescently tagged glutamate receptor protein (shown in green) in active neurons, researchers could follow the protein’s path as the mice learned to fear an electric shock. Neuronal cell bodies appear in blue.
“It’s a first step in visualizing the synapses that encode memories,” says Stephen Maren, director of the neuroscience graduate program at the University of Michigan, who was not involved with the research. “We really haven’t had a tool like this to see memory encoding at a synaptic level. It’s an exciting paper.”

“We are developing techniques that allow us to focus on the actual physical sites that are changing in the brain with learning, at finer and finer resolution,” says the study’s lead investigator, Mark Mayford, associate professor of cell biology at the Scripps Research Institute.

Neuroscientists believe that in order for a memory to form, individual synaptic connections must be strengthened in response to a memory-generating stimulus. This strengthening is likely the result of a specific set of proteins migrating to synapses in a precisely choreographed pattern, but it remains a mystery which proteins are involved and how they are targeted to their destinations. The new study, which appears in today’s issue of Science, is the first to trace a particular protein as it makes its way to particular synapses.

The studied protein is a receptor for glutamate, a neurotransmitter previously implicated in memory formation. The researchers engineered a strain of mice so that the glutamate receptor would glow green under extremely specific, manipulable circumstances.

Via Technology Review