Molecular sponges for brain research

Using novel “molecular sponges”, Max Planck Scientists discover function of microRNA molecules in neuronal development

Messages are sent back and forth in our brains by neurons that connect to each other in complex networks. Neurons develop from stem cells in a complicated process involving a number of different stages. In one of the final stages, tree-like structures called dendrites emerge from the neurons and connect with neighboring neurons via special junctions, the synapses.

Scientists of the Max Planck Research Group around Damian Refojo at the Max Planck Institute of Psychiatry in Munich discovered how the microRNA9 (miR9) helps controlling dendrite growth and synaptic function in mice. MicroRNAs are very short, non-coding RNA molecules that mainly regulate the expression of genes and various cellular activities. To enable a neuron to produce dendrites, miR9 binds to and interferes with the RNA molecules that are needed to make a protein called REST. This protein is a transcription factor switching off the expression of other genes. In effect, miR9 allows a set of genes needed for dendrite growth to be switched on.

“Most importantly we provide a new method to study effects of microRNAs in living organisms”, states Sebastian Giusti, postdoctoral scientist and first author of the current study. “We introduced “molecular sponges” into our mice which can specifically be switched on in single cell types. These sponges are designed to capture particular microRNA molecules, thus inhibiting their action on target molecules.” Using this novel technique, scientist from all fields can now investigate the action of all kinds of microRNAs in living animals.

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