Researchers detect a diffusion barrier inside fly brain
Nervous system requires a glial boundary around a special brain region / Publication in

Date:
November 5, 2021
Source:
University of Mu"nster
Summary:
A team of researchers has now demonstrated the existence of
an internal diffusion barrier in the brain of fruit flies - in
addition to the already known blood-brain barrier.



FULL STORY ==========================================================================
The neurons, located in the brain are interconnected in a complex pattern
and establish special communication points, the synapses. All neurons
require a constant environment in order to function reliably. To ensure
this, the brain is surrounded by the so-called blood-brain barrier. It
ensures, for example, that the nutrient balance always remains the same
and that harmful influences do not reach the neurons. This applies
to all animals including humans. For insects, a team led by Nicole
Pogodalla and Prof. Dr. Christian Kla"mbt from the Institute of Neuro-
and Behavioral Biology at the University of Mu"nster (Germany) has now
shown that there is also a second barrier in the brain. Here glial cells,
too, ensure a spatial separation of different functional compartments,
which is essential for reliable functioning of the nervous system. The
work was published in the online journal Nature Communications.


==========================================================================
The research team studied the insect brain using larvae of the fruit
fly (Drosophila melanogaster) as an example and focused on the role of
glial cells.

Early in development these cells help to establish the correct neuronal
network and later glial cells play important roles in controlling the transmission of signals between neurons. In all invertebrates, as well
as in primitive vertebrates, glial cells also define the outer boundary
of the nervous system - - the blood-brain barrier.

Deep in the fly brain, all synapses are located in a special region
called the neuropil. The neuropil is separated from the zone containing
the cell bodies of the neurons by a small set of surrounding glial
cells, that were in the focus of Nicole Pogodalla. She developed a new experimental approach -- dye injections into living larval brains --
and combined this with cell type specific ablation experiments to show
that these glial cells actually form a diffusion barrier, i. e. regulate
the distribution of molecules.

Since all other cellular barriers in the body are formed by polarized
cells that have an "up" and a "down," the research team next examined
glial cell polarity. Using advanced confocal image analysis as well as
electron microscopy work in combination with state-of-the-art molecular genetics, the researchers uncovered that the ensheathing glial cells are
indeed polarized. They showed that this polarization is functionally
important, as defects in polarity lead to both an altered cell shape
and cause a significant behavioral phenotype in fly larvae: Movement of
larvae with defective or absent glial cells is impaired, and crawling
speed is reduced.

In the current paper, the research team also describes the importance of extracellular matrix -- the tissue lying between cells -, membrane lipids
and membrane proteins, as well as the function of the cytoskeleton in the formation of the barrier-forming glial cells. The study includes extensive electron microscopy data obtained in a collaboration with Dr. Albert
Cardona at the HHMI Janelia Research Campus in Ashburn, VA 20147, USA.

========================================================================== Story Source: Materials provided by University_of_Mu"nster. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Nicole Pogodalla, Holger Kranenburg, Simone Rey, Silke Rodrigues,
Albert
Cardona, Christian Kla"mbt. Drosophila ssHeavy-Spectrin is required
in polarized ensheathing glia that form a diffusion-barrier
around the neuropil. Nature Communications, 2021; 12 (1) DOI:
10.1038/s41467-021- 26462-x ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211105103744.htm

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