KAIST

Professor Eunjoon Kim’s team finds synapse-forming protein

- discover a new protein ‘NGL’ that promotes the formation of neuronal synapses

- can presume the cause of various brain disorders including schizophrenia

- will be published at Nature Neuroscience Vol. 9 in September

A new protein that promotes the formation of synapses in human brains was discovered by a Korean research team. 

The team led by Eunjoon Kim, Professor of Department of Biological Sciences and Head of Creative Research Group of Synapse Formation), announced that it had discovered a new fact that NGL protein promotes the formation of neuronal synapses and this fact would be published in Nature Neuroscience Vol. 9 on September 18. 

Professor Kim’s team discovered that a membrane protein named ‘NGL’ located at post synapse links with other membrane protein named netrin-G in pre synapse, acting as crosslink, and promotes the formation of a new synapse. 

‘NGL’ is the second protein found to crosslink synapse, following neuoroligin. With the discovery of this new protein, the principle of synapse formation and the causes of various brain disorders can be presumed. 

In the human brain, about more than 100 billion neuron cells and about 10,000 synapses compose neural circuit. A synapse is the place where innervation occurs between neuron cells. The formation of synapse induces the formation of neural circuit, and neural circuit is deeply related with various brain disorders as well as normal development of brains or brain functions. 

“As netrin-G linked with NGL is related with schizonphrenia and neuoroligin and synapse crosslinking protein having a similar function with NGL is deeply related with mental retardation and autism, I think NGL is related with various brain disorders including schizophrenia.” 

<Explanation of attached photos> 

■ Photo1: Experiment for confirming NGL’s ability to form synapse No. 1

Mix ordinary cell (green) revealing NGL at its surface and neuron cell. Axon grows toward NGL (ordinary cell) located in the middle of ten o’clock direction and meets NGL, where NGL induces the formation of pre synapse (red) in the contacting axon.

Whether pre synapse has been formed can be told by the fluorescent dying (red) of pre synapse protein named Synapsin. 

- Figure a-b: formation of synapse by NGL

- Figure c-d: transformed NGL losing synapse forming ability cannot form synapse 

■ Photo 2: Experiment for confirming NGL’s ability to form synapse No. 2

When beads coated with NGL are scattered on neuron cell, the beads contact with the axon of the neuron cell (the beads are clearly visible at the phase differentiation image in the middle panel). At this time, NGL induces the formation of pre synapse (red) in the axon. Whether pre synapse has been formed can be told by the fluorescent dying (red) of pre synapse protein named SynPhy (panel a) or VGlut1 (panel b).