The mammalian brain has billions of synaptic connections, which is more than a little difficult to sort and map out. Today’s image is from a group of biologists who used their own brilliant synaptic connections and developed a technique for mapping out these connections in mammals.
One of the most commonly used fluorescent markers in cell biology is GFP, which stands for Green Fluorescent Protein. Scientists have been very creative in using this powerful tool to understand more about cell biology. For example, GRASP (GFP reconstitution across synaptic partners) is a technique developed a few years back in order to map out synaptic connections in worms and flies. In GRASP, one half of the GFP protein is expressed in one type of neuron, while the other half of GFP is expressed in a different type of neuron. Alone, each of these GFP fragments cannot fluoresce, but when the two neurons are close together in a synaptic connection, the GFP will fluoresce green light that pinpoints the location of a connection. Recently, a group of biologists made major modifications in this technique in order for it to work in mammals, whose synaptic architecture can vary a lot from flies and worms. In the images above, dendrites (red) in a mouse brain intersect with axons (blue), as seen as the green GRASP signal.
Kim, J., Zhao, T., Petralia, R., Yu, Y., Peng, H., Myers, E., & Magee, J. (2011). mGRASP enables mapping mammalian synaptic connectivity with light microscopy Nature Methods, 9 (1), 96-102 DOI: 10.1038/nmeth.1784
Adapted by permission from Macmillan Publishers Ltd, copyright ©2011