Researchers Create Larger Than Life Synapse

Giant synapses make it easier for scientists to observe events happening within and it last longer than fresh brain slices.

AsianScientist (Apr. 19, 2016) – Researchers from the Okinawa Institute of Science and Technology Graduate University (OIST) and Doshisha University in Japan have discovered a method to create a synapse that is large enough to allow them to directly monitor events occurring inside its structure. Their work was published in The Journal of Neuroscience.

One key element to understanding brain functions related to memory, movement and thinking are the synapses. A synapse is the contact point between two neurons, where a signal is transmitted from one neuron to another—specifically, from the pre-synaptic part of one neuron, to the post-synaptic part of another neuron.

This communication process involves many types of proteins, and allows us, for example, to memorize a friend’s name. Moreover, synapses do not just pass ‘messages’ from one neuron to another, but also keep the strength of transmitting such messages for a short or a long period of time, thus playing a main role in memory formation.

Synaptic malfunction is thought to underlie the early stages of neuro-degenerative diseases, like Parkinson’s and Alzheimer’s diseases. However, a problem when studying synapses is that they are too small for direct access with recording tools. Even with a powerful microscope, it is difficult to see what is happening within a single synapse.

Freshly prepared brain slices can provide researchers with big synapses, but they deteriorate fast, and can be kept and studied only for one day. Such a short period does not allow researchers to perform experiments linked with the molecular composition of neurons and gene expression inside neurons: experiments that involve proteins created inside neurons. To top it all off, brain slices are densely packed with cells, and are not transparent enough to perform high resolution imaging studies.

Conventional culture preparations, on the other hand, are viable for longer periods and their simple cell layer organization makes them ideal for microscopy imaging. But the size of the individual synapse is too small to show what is happening inside the synapse in detail.

Professor Tomoyuki Takahashi, Dr. Dimitar Dimitrov and colleagues from the OIST Cellular and Molecular Synaptic Function Unit wanted to combine the advantages of the two techniques to produce big synapses in culture.

“Initially, it was not possible to consistently reproduce these big synapses in culture,” Dimitrov said. “Then we discovered some specific factors that are needed to promote the formation of the giant synapses.”

In the present study, Dimitrov and colleagues describe a new method to grow giant synapses in culture dishes. In these giant synapses, the pre-synaptic part of one neuron does not just ‘touch’ the post-synaptic part of another neuron, but instead wraps around the whole cell body of the post-synaptic neuron.

The giant synapse culture has already shown some encouraging results in this research direction. Scientists were able to record live images of the synapse in high resolution while simultaneously recording the electrical signals that were transmitted between the neurons.

“This technique has a huge potential to help us understand how the synapses work. It will provide better, deeper understanding as to what is happening in the synapses,” Takahashi said.

The next step will be to use this model to explore how the proteins relate to the strength of the message transmission in the pre-synaptic part of one neuron.


The article can be found at: Dimitrov et al. (2016) Reconstitution of Giant Mammalian Synapses in Culture for Molecular Functional and Imaging Studies.

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Source: Okinawa Institute of Science and Technology Graduate University.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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