As the brain develops, neuronal axons extend outward in search of other neurons, all the while receiving ‘directions’ from the extracellular environment in the form of chemical signals that indicate when and where these growing axons should turn.
For example, axons exposed to a gradient distribution of nerve growth factor (NGF) protein will automatically steer in the direction of highest NGF concentration.
“NGF is one of the most extensively studied molecules that direct axon elongation,” explains Hiroyuki Kamiguchi of the RIKEN Brain Science Institute in Wako. “However, it has remained unclear for a long time how axons change the direction of elongation in response to NGF.”
NGF-mediated turning is facilitated in part by the cellular signaling molecule inositol trisphosphate (IP3), which in turn governs the intracellular release of calcium ions—an essential component of NGF’s chemo-attractive action. By applying advanced methods for molecular-resolution live cell imaging, Kamiguchi and his colleagues have now gained valuable insights into how this process directs axonal guidance1.
The researchers cultured chick-derived neurons expressing a genetically encoded sensor that fluoresces at specific wavelengths in the presence of IP3, and then observed how individual neurons responded to an NGF gradient in the vicinity of the growth cone—the leading edge of a growing axon. They immediately noted the establishment of an asymmetric distribution of IP3 within the growth cone and an elevated signal on the growth cone side exposed to higher NGF levels; this is mirrored by a similarly uneven distribution of IP3-induced calcium release. This asymmetry correlates directly with axonal turning such that the growth cone steers in the direction established by the highest levels of NGF, IP3 and calcium ion (Ca2+) release.
The development of techniques for accurately detecting potentially subtle variations in IP3 distribution was a key component of their success in this work. “We needed to detect 1% differences in fluorescence emission from the IP3 sensor between both sides of the growth cone,” says Kamiguchi.
However, he considers even the mere existence of such a gradient across the 10–20 micron width of the growth cone to be fairly surprising. “Because IP3 diffuses so rapidly in cytoplasm, it has not been viewed as a highly localized messenger,” he says. “This suggests the existence of robust degradation machinery to localize IP3 signals to one side of the growth cone.”
These insights into how neurons establish direction-specific signaling profiles should provide helpful starting points for understanding other models of cell polarization and migration.
The corresponding author for this highlight is based at the Laboratory for Neuronal Growth Mechanisms, RIKEN Brain Science Institute.
Saeko Okada | Research asia research news
Further reports about: > Brain > IP3 receptors > NGF > NGF concentration > RIKEN > Science TV > asymmetric distribution > axonal guidance1 > cellular signaling molecules > chemo-attractive action > molecular-resolution live cell imaging > neurons > spatial distribution of cellular signaling molecules
Make way for the mini flying machines
21.03.2018 | American Chemical Society
New 4-D printer could reshape the world we live in
21.03.2018 | American Chemical Society
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.
In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...
Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...
19.03.2018 | Event News
16.03.2018 | Event News
13.03.2018 | Event News
21.03.2018 | Physics and Astronomy
21.03.2018 | Materials Sciences
21.03.2018 | Life Sciences