For the first time ever, scientists have witnessed the formation of a protein crucial to memory formation.
In a “technological tour-de-fouce,” scientists at the Albert Einstein College of Medicine of Yeshiva University used advanced imaging techniques and a never-before-seen mouse model to observe the formation and transportation of beta-actin protein, which is thought to be crucial to strong synaptic connections. Two papers published in Science report on the findings.
Hye Yoon Park, PhD and postdoctoral student, spent three years developing a mouse model that produces fluorescently tagged messenger RNA–the molecule that provides instruction for protein-synthesis–for beta-actin protein.
Dendrites–the spindly “fingers” of neurons–come together at synapses, structures that allow the transportation of neurotransmitters from one neuron to the next. Memories are thought be formed when synapses are strengthened and stabilized by electrical impulses, which change the shape of the dendrites. Beta-actin is thought to play a role in the shape-shifting of dendrites and thus the strengthening of synapses–and memories.
When she stimulated the mouse’s hippocampus—the area of the brain that forms and stores memories—Park observed beta-actin mRNA forming in the nuclei of neurons and travelling down to the dendrites, where the protein would be synthesized.
The second paper describes the work of graduate student Adina Buxbaum, who made a remarkable discovery about the unique way in which neurons regulate the production of beta-actin protein.
“Having a long, attenuated structure means that neurons face a logistical problem,” said Robert Singer, Ph.D., the senior author of both papers and professor and co-chair of Einstein’s department of anatomy & structural biology and co-director of the Gruss Lipper Biophotonics Center at Einstein, in a press release. “Their beta-actin mRNA molecules must travel throughout the cell, but neurons need to control their mRNA so that it makes beta-actin protein only in certain regions at the base of dendritic spines.”
To prevent the synthesis of more protein than needed, it seems that the mRNA is “packaged” into tiny granules. When neurons are stimulated, these granules fall apart, freeing up mRNA for synthesis. Buxbaum observed that after a few minutes, the free-floating mRNA becomes repackaged.
It seems that neurons have developed an “ingenious” method to control their memory-making proteins.