11. September 2020

“Glial cells” play an active role in the nervous system “Glial cells” play an active role in the nervous system

Researchers from the Universities of Münster and Bonn study the signal transduction in the brain

For the brain to work efficiently, nerve impulses must reach their destination as quickly and precisely as possible. The nerve fibres, also known as axons, pass on the impulses, and an insulating sheath around the axons increases their speed of conduction in vertebrates. This insulating sheath, called myelin, is formed by a major component of the brain – the glial cells. Researchers at the University of Münster, in collaboration with colleagues at the University of Bonn, have now discovered that glial cells not only influence the speed of nerve conduction, but also the precision of signal transduction. In the absence of these insulating sheaths, short-circuit-like processes occur. The study has been published in the journal “Nature Communications”.

View of a Drosophila larva (with the head turned to the left). - The surrounding glial cells in the peripheral nervous system have been depicted in individual colours by using a genetic trick. To this end, a random combination of a certain set of fluorescent proteins is induced in the surrounding glial cells by means of a systematic expression of a recombinase so that each cell expresses its own colour code and, as a result, becomes visible under the microscope. © Klämbt Lab

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Glial cells are notonly indispensable for providing energy – they also have a broad range of othertasks in the brain. They are responsible for transport of metabolite andxenobiotics, regulating fluid exchanges, and maintaining ion homeostasis. Inorder to better understand the importance of glial cells for neuronal signalling,the researchers studied changes in behaviour after the induced activation ofindividual neurones in fruit flies (Drosophilamelanogaster). “For this purpose we either removed individual glial cellsfrom the nervous system or specifically disturbed their development concomitantto a light-induced, optogenetic, neuronal activation,” says lead author Prof. ChristianKlämbt from the Institute of Neuro- and Behavioural Biology at MünsterUniversity. As a result of these activities, the researchers were first able toascertain that glial cells control the radial growth of the axons.

Analysis of the movement behavior of fruit flies

In order todetermine the performance of the axons, Dr. Andreas Schoofs from the researchgroup of Prof. Michael Pankratz at the LIMES Institute at the University ofBonn carried out electrophysiological measurements. The researchers found, thataxons without wrapping glia cells have, as expected, a slower conduction speed.Astonishingly, it became apparent that the changes in movement behavior are causedonly to a minor degree by a slower conduction speed. The more importantcontribution made here by glial cells is the formation of membrane processesbetween individual axons – which prevents electrical coupling (i.e. shortcircuits) and thus makes a decisive contribution to the precision of neuronalsignalling.

The researchersundertook a detailed analysis of larval locomotion by means of a special custommade device. The development of the so-called FIM (Frustrated total internalreflection-based Imaging Method), together withself-developed software, allows a high-resolution depiction and analysis ofmovements made by even minute organisms.

The function ofglial cells as active modulators of the speed and, in particular, the precisionof stimulus conduction, has not previously been described. “What our researchmakes clear is the role played by glial cells as active components in thenervous system,” says Christian Klämbt. “With these new findings we arecreating a basis for a better understanding of some of the symptoms of diseasesof the nervous system.” These include Multiple Sclerosis and MorbusCharcot-Marie-Tooth.

The research workwas funded by the German Research Foundation (DFG).

Publication: Kottmeier, R., Bittern, J., Schoofs, A., Scheiwe, F., Matzat, T., Pankratz, M., Klämbt, C. (2020): Wrapping glia regulates neuronal signaling speed and precision in the peripheral nervous system of Drosophila. Nature Communications; https://doi.org/10.1038/s41467-020-18291-1