Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mathematical model helps show how zebrafish get their stripes

18.11.2015

A mathematical model developed by Brown University researchers is shedding new light on how zebrafish get their iconic stripes. The model helps to demonstrate how two dynamic processes--the movement of pigment cells across the skin, and the birth and death of cells as the fish grows--combine to keep zebrafish stripes in line.

The model is described in the Journal of the Royal Society Interface.

Zebrafish have become quite a popular model organism for biology researchers over the past few decades. The small freshwater fish begin life as transparent embryos and develop in just a few months to full size, giving scientists the chance to watch their development in detail.


A mathematical model simulates the formation of stripes over a zebrafish's lifetime. Each box represents a snapshot of the growth period.

Credit: Volkening/Sandstede/Brown University

The emergence of their namesake stripes of dark blue and bright yellow has been the subject of much research. The stripes have been shown to be the result of interplay between three types of pigment cells: black melanophores, yellow xanthophores, and silvery iridophores.

"The stripe pattern forms dynamically as the fish develops," said Alexandria Volkening, a graduate student and Brown's Division of Applied Mathematics and the lead author on the new paper. "It's not like these pigment cells are filling out some kind of prepattern that's already there. It's the interactions of the cells over time that causes the patterns to form. We wanted to build a model that simulates this based as much as possible on what's known about the biology."

... more about:
»Zebrafish »pigment cells »stem cells »stripe

The model Volkening developed treats cells as individual agents, behaving according to a set of rules derived from experiments. It directly incorporates two types of cells: the black melanophores and the yellow xanthophores. The effects of the third cell type, the iridophores, are implicit in the behavior of the other two cells, though the iridophores themselves are not physically included in the model.

The model starts with melanophores and xanthophores arranged in a way that mimics the arrangement of cells in fish just a few weeks old. The model domain then grows in a way that approximates the growth of the fish. As the domain grows, new cells are added that mimic the stem cells from which pigments are derived in actual fish.

The stem cells take cues on which type of cell to become from existing pigment cells. Those cues come both from cells in the immediate vicinity, and from cells further away. Experiments in actual fish have suggested that both short- and long-distance communication is important.

In the model, if a new stem cell is surrounded by black cells and the adjacent developing stripe regions are yellow, it has a much greater chance of becoming a dark cell itself. The same goes for yellow cells. Cell death is controlled by similar mechanism. A black cell surrounded on all sides by light ones or without sufficient yellow cells in adjacent stripe regions has a much higher probability of dying.

Experiments have shown that pigment cells also have the ability to move short distances across the fish's skin, and the model captures that dynamic as well. The pigments are thought to move according to cues communicated from surrounding cells. In the model, all of the cells repel each other, but different cell types have a stronger repulsion than like cells. The movement cues are gathered from the cells immediately surrounding a pigment cell.

Using these rules over the normal growth period of an actual fish, model was able to successfully recreate the development of stripes as seen in experiments. It was also able to recreate the results of a variety of experiments biologists have done to perturb stripe formation. For example, scientists have ablated pigment cells early in a fish's development to see how it would affect stripe development. Those experiments showed that when cells are knocked out, the fish form oblong spots rather then stripes as they continue to develop. The model was able to recreate those effects.

Once they had a model that could reconstruct actual experiments, the researchers could test how different cellular dynamics influence stripe growth.

"One thing that's not clear is the role of birth and death versus movement. Do you need both or just one?" said Bjorn Sandstede, chair of Brown's Division of Applied Mathematics and a co-author of the paper. "What we can do in the model is turn off one of the two and see what we get."

With movement turned off, the model showed that cells formed oblong blobs with no particular orientation. With birth and death turned off, like cells formed tightly packed spots rather than stripes. Taken together, the results help to confirm the interdependent dynamics of the two processes in the development of the stripe pattern.

Sandstede says that simulations like these are important because they offer a window into how complex patterns and structures form dynamically in nature. "If you look at any kind of organism, they start with oocytes, which are roundish structures with little spatial differentiation at all, and you end up with organisms like us that have a complex spatial structure," he said. "I think it's important to try to understand how spatial differentiation occurs. Zebrafish and their stripes are a good model to do that because you can identify the different cells and what they're doing in the process."

Volkening says she plans to continue to refine the model to better capture the effects of iridophores that were not directly included in the current model. She hopes the model can serve as a guide for future experiments in actual fish.

"One of the benefits of the models is that we can do this in six minutes," she said. "It takes weeks to grow the fish," Volkening said.

###

Note to Editors:

Editors: Brown University has a fiber link television studio available for domestic and international live and taped interviews, and maintains an ISDN line for radio interviews. For more information, call (401) 863-2476.

Kevin Stacey | EurekAlert!

Further reports about: Zebrafish pigment cells stem cells stripe

More articles from Life Sciences:

nachricht Researchers identify potentially druggable mutant p53 proteins that promote cancer growth
09.12.2016 | Cold Spring Harbor Laboratory

nachricht Plant-based substance boosts eyelash growth
09.12.2016 | Fraunhofer-Institut für Angewandte Polymerforschung IAP

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>