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 One step closer to reality
20.04.2018 | Max-Planck-Institut für Entwicklungsbiologie

nachricht The dark side of cichlid fish: from cannibal to caregiver
20.04.2018 | Veterinärmedizinische Universität Wien

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Magnetic nano-imaging on a table top

20.04.2018 | Physics and Astronomy

Start of work for the world's largest electric truck

20.04.2018 | Interdisciplinary Research

Atoms may hum a tune from grand cosmic symphony

20.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>