Max Planck researchers discover that a Doppler effect influences segmentation
Many animals exhibit segmental patterns that manifest themselves during development. One classical example is the sequential and rhythmic formation the segmental precursors of the backbone, a process that has been linked to the ticking of an oscillator in the embryo – the “segmentation clock”.
Waves of oscillating gene expression are visible in pseudo-colour sweeping from the posterior to the anterior through the unsegmented tissue. The anterior end of this unsegmented tissue moves steadily into these on-coming waves, creating a Doppler effect that contributes to the rhythm of segmentation.
© Max Planck Institute of Molecular Cell Biology and Genetics
Until now, this patterning process was thought to be determined simply by the time scale of genetic oscillations that periodically trigger new segment formation. However, Max Planck researchers suggest a more nuanced control over the timing of segmentation.
Their findings show that the rhythm of segmentation is influenced by a Doppler effect that arises from gene expression waves occurring in a shortening embryonic tissue. They paint a potentially revolutionary picture of the process of developmental segmentation, one controlled by not only the time scale of genetic oscillations, but also by changes in oscillation profile and tissue shortening.
What do you, I and many other animals have in common? Perhaps it isn’t the first thing you think of, but we, like them, have a distinctly segmented body axis. During our development, spatial and temporal cues are integrated to form a specific number of embryonic segments that later on give rise to corresponding ribs and vertebrae. The rhythm of this patterning process is crucial to determine the correct number and size of segments, but how is its timing actually controlled?
In vertebrates, the onset and arrest gene expression waves is thought to be controlled by a complex genetic network – the so-called “segmentation clock”. Each arrested waves triggers the formation of a new segment. The underling mechanism was thought to operate like a conventional clock that ticks with a precise period: one tick of the clock equals one new segment.
To examine this hypothesis a team of biologists and physicists guided by Andy Oates and Frank Jülicher from the Max Planck Institute of Molecular Cell Biology and Genetics together with colleagues from the Max Planck Institute for the Physics of Complex Systems in Dresden developed a novel transgenic zebrafish line (named Looping) and a multidimensional time-lapse microscope that enabled them to visualise and quantify gene expression waves and segment formation at the same time.
To their surprise they found that the onset and arrest of waves happened with a different frequency, indicating that the timing of segmentation cannot be explained by a conventional clock alone. The team worked out that this puzzling difference in frequency was caused by a scenario that is similar to the classic Doppler effect.
Travelling tissue and oscillating genes
Imagine an ambulance driving down the street. Did you ever notice how the pitch of the siren changes as it drives past? This is the Doppler effect, and is caused by changes in the frequency of the sound waves as the source comes towards an observer (you) and then drives away. The same thing would happen if you rapidly approached and then passed a stationary sound source.
It turns out that sound waves are not entirely unlike the gene expression waves in zebrafish. These gene expression waves travel from the posterior towards the anterior of the animal (from the tip of the tail towards the head). As they do, the embryo develops, changing its shape, and the tissue in which the waves travel shortens. This leads to a relative motion of the anterior end of the tissue where the new segments form (the observer) towards the posterior (the source).
This motion of the observer into travelling gene expression waves leads to a Doppler effect in the developing zebrafish embryo. Moreover, this Doppler effect is modulated by a more subtle effect that is caused by a continuously changing wave profile. This Dynamic Wavelength effect and the Doppler effect have an opposing influence on the timing of segmentation, but the effect of the Doppler is stronger. Since this timing, as mentioned above, determines the number and size of the body segments, it affects the number and size of the developing ribs and vertebrae.
The team’s findings could potentially revolutionise our understanding of timing during development. The biological mechanism behind the change in the wave profile is still unclear, but it highlights the complex nature of development and the need to go beyond steady state and scaling descriptions of embryonic development.
Florian Frisch | Max-Planck-Institute
Chains of nanogold – forged with atomic precision
23.09.2016 | Suomen Akatemia (Academy of Finland)
Self-assembled nanostructures hit their target
23.09.2016 | King Abdullah University of Science and Technology
The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has been developing various applications for OLED microdisplays based on organic semiconductors. By integrating the capabilities of an image sensor directly into the microdisplay, eye movements can be recorded by the smart glasses and utilized for guidance and control functions, as one example. The new design will be debuted at Augmented World Expo Europe (AWE) in Berlin at Booth B25, October 18th – 19th.
“Augmented-reality” and “wearables” have become terms we encounter almost daily. Both can make daily life a little simpler and provide valuable assistance for...
With the help of artificial intelligence, chemists from the University of Basel in Switzerland have computed the characteristics of about two million crystals made up of four chemical elements. The researchers were able to identify 90 previously unknown thermodynamically stable crystals that can be regarded as new materials. They report on their findings in the scientific journal Physical Review Letters.
Elpasolite is a glassy, transparent, shiny and soft mineral with a cubic crystal structure. First discovered in El Paso County (Colorado, USA), it can also be...
For the first time, Fraunhofer IKTS shows additively manufactured hardmetal tools at WorldPM 2016 in Hamburg. Mechanical, chemical as well as a high heat resistance and extreme hardness are required from tools that are used in mechanical and automotive engineering or in plastics and building materials industry. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden managed the production of complex hardmetal tools via 3D printing in a quality that are in no way inferior to conventionally produced high-performance tools.
Fraunhofer IKTS counts decades of proven expertise in the development of hardmetals. To date, reliable cutting, drilling, pressing and stamping tools made of...
At AKL’16, the International Laser Technology Congress held in May this year, interest in the topic of process control was greater than expected. Appropriately, the event was also used to launch the Industry Working Group for Process Control in Laser Material Processing. The group provides a forum for representatives from industry and research to initiate pre-competitive projects and discuss issues such as standards, potential cost savings and feasibility.
In the age of industry 4.0, laser technology is firmly established within manufacturing. A wide variety of laser techniques – from USP ablation and additive...
Every three years, the plastics industry gathers at K, the international trade fair for plastics and rubber in Düsseldorf. The Fraunhofer Institute for Laser Technology ILT will also be attending again and presenting many innovative technologies, such as for joining plastics and metals using ultrashort pulse lasers. From October 19 to 26, you can find the Fraunhofer ILT at the joint Fraunhofer booth SC01 in Hall 7.
K is the world’s largest trade fair for the plastics and rubber industry. As in previous years, the organizers are expecting 3,000 exhibitors and more than...
23.09.2016 | Event News
20.09.2016 | Event News
16.09.2016 | Event News
23.09.2016 | Life Sciences
23.09.2016 | Health and Medicine
23.09.2016 | Life Sciences