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
Atomic-level motion may drive bacteria's ability to evade immune system defenses
24.04.2017 | Indiana University
Two-dimensional melting of hard spheres experimentally unravelled after 60 years
24.04.2017 | University of Oxford
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
24.04.2017 | Physics and Astronomy
24.04.2017 | Materials Sciences
24.04.2017 | Life Sciences