During neural development, immature nerve cells extend axons and dendrites toward their targets then form connections with other cells. At the tip of these extending fibers is the growth cone, a structure with finger-like protrusions called filopodia.
As the growth cone moves like an amoeba through the environment, the filopodia detect chemical guidance cues that steer it in the right direction. These processes are dependent on rearrangements of the actin cytoskeleton, a protein scaffold inside the cell.
Now, a team of researchers led by Hiroyuki Kamiguchi of the RIKEN Brain Science Institute has shown that nerve fibers turn clockwise in the absence of external clues, when growing on flat two-dimensional surfaces, because the filopodia rotate of their own accord.
The researchers first confirmed that nerve fibers from the hippocampus of embryonic rats turn rightwards when grown on a two-dimensional substrate, but grow straight when embedded in a three-dimensional gel. Addition of the fungal toxin cytochalasin D, which stops elongation of actin filaments, prevented the turning of fibers growing on a flat surface, showing that the turning is dependent on the cytoskeleton.
Hypothesizing that filopodia rotate autonomously, the researchers developed a new technique to directly observe the movements in three dimensions. They embedded hippocampal neurons in a gel, so the nerve fibers grew vertically towards the lens of an upright microscope. This revealed that individual filopodia tended to rotate counter-clockwise. This rotation generates a leftward force on the surface, causing the growth cone to turn to the right.
The researchers then tested whether or not this turning is powered by myosins, the motor proteins responsible for actin-based cellular movements. They transfected hippocampal neurons with three different full-length myosins (Va, Vb and Vc), as well as shortened forms of them that prevent endogenous myosin molecules from binding actin filaments. All were fused to, or co-expressed with, a fluorescent protein to allow easy visualization.
As expected, filopodial rotation was blocked in neurons expressing the shortened myosins, but could be rescued by transfecting the cells with myosins Va and Vb, but not myosin Vc. The rightwards rotation was also observed in neurons from the cerebral cortex, thalamus and cerebellum, suggesting that this is a general mechanism.
Commenting on the findings, Kamiguchi says that: “Rotating filopodia would probe a larger volume of the environment and contribute to the precise perception of cues by the growth cone.”Alternatively, the rotations could promote nerve bundle formation, by enabling new fibers to twine around older ones.
The corresponding author for this highlight is based at the Laboratory for Neuronal Growth Mechanisms, RIKEN Brain Science Institute
1. Tamada, A., Kawase, S., Murakami, F., & Kamiguchi, H. Autonomous right-screw rotation of growth cone filopodia drives neurite turning. Journal of Cell Biology published online 1 February 2010 (doi:10.1083/jcb.200906043).
gro-pr | Research asia research news
Zebrafish's near 360 degree UV-vision knocks stripes off Google Street View
22.06.2018 | University of Sussex
New cellular pathway helps explain how inflammation leads to artery disease
22.06.2018 | Cedars-Sinai Medical Center
In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.
Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...
Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...
Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.
Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...
The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.
Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.
An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.
Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...
13.06.2018 | Event News
08.06.2018 | Event News
05.06.2018 | Event News
22.06.2018 | Materials Sciences
22.06.2018 | Earth Sciences
22.06.2018 | Life Sciences