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Distinct wiring mode found in chandelier cells
A basic tenet of neural development is that young neurons make far more connections than they will actually use, with very little specificity. They selectively maintain only the ones that they end up needing. Once many of these connections are made, the brain employs a use-it or lose-it strategy; if the organism’s subsequent experiences stimulate the synapse, it will strengthen and survive. If not, the synapse will weaken and eventually disappear.

Researchers from Hiroki Taniguchi’s lab at the Max Planck Florida Institute for Neuroscience (MPFI) published a study in eNeuro in May 2017 showing for the first time that a unique type of inhibitory interneuron called chandelier cells – which are implicated in several diseases affecting the brain such as schizophrenia and epilepsy – seem to develop their connections differently than other types of neurons.

Neurons have several dendrites – thin protrusions through which they receive input from many other cells, but only one axon, where all the information the cell receives is integrated and sent as a single outgoing signal. Most cells’ axons reach out and form synapses on other cells’ dendrites or cell bodies, but chandelier cells exclusively inhibitory synapse on other cells’ axon initial segments (AIS), right where the cell begins to send its own signal down the axon. At this location, the chandelier cells have a greater impact on other cell’s behavior. “Chandelier cells are the final gatekeeper of the action potential,” said Dr. Taniguchi. “We believe this role makes them an especially important factor in controlling epilepsy, where over-excitement spreads throughout the brain unchecked”.

Using their own recently-developed genetic labeling techniques for tracking these cells in early development in mice, Taniguchi and his team observed that, like most neurons, the cells remodeled their axonal organization through development. They also found excessive axonal varicosities that have been considered morphologically synaptic structures.
To investigate whether these varicosities actually contained synaptic molecules, the team expressed synaptic markers in the chandelier cells using transplantation techniques.

What they found was surprising. Only those varicosities that were associated with the AIS contained synapses – the rest appeared to be empty throughout development. This was also corroborated by their ultrastructures obtained with electron microscopy. These findings provide a big clue to understanding how this important cell type properly wires a unique circuit.

Source & further reading:
https://www.maxplanckflorida.org/news-and-media/news/distinct-wiring-mode-found-in-chandelier-cells/

Journal article:
http://www.eneuro.org/content/4/3/ENEURO.0057-17.2017

Gif: Brain biology by MIT

#neuroscience #medicine #neurons #brain #research #chandeliercells
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Parkinson’s Is Partly An Autoimmune Disease, Study Finds
Researchers have found the first direct evidence that autoimmunity — in which the immune system attacks the body’s own tissues — plays a role in Parkinson’s disease, the neurodegenerative movement disorder. The findings raise the possibility that the death of neurons in Parkinson’s could be prevented by therapies that dampen the immune response.

The study, led by scientists at Columbia University Medical Center (CUMC) and the La Jolla Institute for Allergy and Immunology, was published in Nature.

“The idea that a malfunctioning immune system contributes to Parkinson’s dates back almost 100 years,” said study co-leader David Sulzer, PhD, professor of neurobiology (in psychiatry, neurology, and pharmacology) at CUMC. “But until now, no one has been able to connect the dots. Our findings show that two fragments of alpha-synuclein, a protein that accumulates in the brain cells of people with Parkinson’s, can activate the T cells involved in autoimmune attacks.

“It remains to be seen whether the immune response to alpha-synuclein is an initial cause of Parkinson’s or if it contributes to neuronal death and worsening symptoms after the onset of the disease,” said study co-leader Alessandro Sette, Dr. Biol. Sci., professor in the Center for Infectious Disease at La Jolla Institute for Allergy and Immunology in La Jolla, Calif. “These findings, however, could provide a much-needed diagnostic test for Parkinson’s disease and could help us to identify individuals at risk or in the early stages of the disease.”

Source and further reading:
http://newsroom.cumc.columbia.edu/blog/2017/06/21/parkinsons-is-partly-an-autoimmune-disease-study-finds/

Journal article:
http://www.nature.com/articles/nature22815

#neuroscience #Parkinson's #alphasynuclein #immunesystem #dopaminergicneurons
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