The human brain consists of a hundred billion nerve cells, each of which makes thousands of connections with other cells. In all of this, how do nerve fibers know where to grow and when to establish a contact?
Scientists at the Max Planck Institute of Neurobiology in Martinsried now found a protein that guides growing nerve cells in the eye of the fruit fly. In addition, the protein also acts as spacer between neighboring nerve cells. Similar mechanisms could also play a role in the development of the vertebrate nervous system.
Finding your way in a large and unknown city without the aid of a navigational device or a fellow passenger is tough: each intersection requires a new decision on the right way to go, while at the same time dozens of traffic rules need to be observed and collisions to be omitted.
In a very similar situation are young nerve cells, when they try to find their way in their "megacity", the brain. In a vast tangle of other cells, growing nerve cells have to decide at numerous points in which direction to continue in order to find the cell they need to contact. To make this task even more difficult, thousands of other nerve cells have the same aim and project their cell extensions (axons) towards their partner cells. Unwanted collisions between these cells could thus quickly lead to a "traffic jam" with severe consequences: functional impairment is often the result when a nerve cell is unable to contact its partner cell.
What guides a nerve cell to its target?
In order to answer this question, scientists of the Max Planck Institute of Neurobiology took a closer look at the eye development of the fruit fly Drosophila. The eye of the fruit fly is especially suited for such research: It is much simpler than that of a vertebrate and thus easier to study. At the same time, it is complex enough to elucidate the general mechanisms responsible for neuronal path-finding. Another benefit of choosing the fruit fly is that a wide variety of genetic tools are available. This enables scientists for example to alter genes specific to the development of the eye while all other nerves remain untouched. And this is exactly what the neurobiologists have done: they specifically disabled a gene in the fly eye and found its product, the protein Gogo (Golden Goal), which not only functions as a navigational aid for growing nerve cells, but also maintains the spacing between neighboring cells.
Truly a complex eye
The compound eye of the fruit fly consists of 800 independent photoreception units, each of which contains eight photoreceptor cells. These specialized nerve cells convert light into electrical signals which are transported to the brain. The axon of each receptor cell grows during the eye's development towards the next site of neuronal processing, the lamina. Parallel growth of the eight axons results in the formation of the visual rod in the center of each photoreceptor unit. Reaching the lamina, two of the eight axons continue to grow to the next brain layer, the medulla. On their way to the medulla, the visual pathways cross each other, resulting in a rotation of 180° of the original picture. The Max Planck scientists now showed how nerve cells find their correct partner cells in this complex growth pattern: The protein Gogo is located in the membrane right at the tip of the growing axon. In the absence of Gogo due to genetic manipulation, cells are unable to maintain their parallel growth - they collide and clump together and the visual rod cannot form. In addition, the two axons that continue to grow towards the medulla are unable to find their partner cell - they stray before or overshoot their correct target layer (Figure 1). It is thus clear: the fly eye cannot develop correctly without Gogo.Navigational aid also for other nerve systems?
Original publication:Tatiana Tomasi, Satoko Hakeda-Suzuki, Stephan Ohler, Alexander Schleiffer, Takashi Suzuki
Neuron, 13 March 2008Contact
Dr. Stefanie Merker | idw
Funding of Collaborative Research Center developing nanomaterials for cancer immunotherapy extended
28.06.2017 | Johannes Gutenberg-Universität Mainz
Zeolite catalysts pave the road to decentral chemical processes Confined space increases reactivity
28.06.2017 | Technische Universität München
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
28.06.2017 | Physics and Astronomy
28.06.2017 | Physics and Astronomy
28.06.2017 | Health and Medicine