scholarly journals The periodic coloration in birds forms through a prepattern of somite origin

Science ◽  
2018 ◽  
Vol 361 (6408) ◽  
pp. eaar4777 ◽  
Author(s):  
Nicolas Haupaix ◽  
Camille Curantz ◽  
Richard Bailleul ◽  
Samantha Beck ◽  
Annie Robic ◽  
...  
Keyword(s):  
Expression Profile ◽  
Natural Variation ◽  
Reaction Diffusion ◽  
Positional Information ◽  
Pigment Production ◽  
Periodic Patterns ◽  
Local Dynamics ◽  
Step Process ◽  
Early Developmental ◽  
Dose Dependent

The periodic stripes and spots that often adorn animals’ coats have been largely viewed as self-organizing patterns, forming through dynamics such as Turing’s reaction-diffusion within the developing skin. Whether preexisting positional information also contributes to the periodicity and orientation of these patterns has, however, remained unclear. We used natural variation in colored stripes of juvenile galliform birds to show that stripes form in a two-step process. Autonomous signaling from the somite sets stripe position by forming a composite prepattern marked by the expression profile of agouti. Subsequently, agouti regulates stripe width through dose-dependent control of local pigment production. These results reveal that early developmental landmarks can shape periodic patterns upstream of late local dynamics, and thus constrain their evolution.

scholarly journals A defined platform of human peri-gastrulation-like biological fate patterning reveals coordination between Reaction-Diffusion and Positional-Information

2017 ◽  
Author(s):  
Mukul Tewary ◽  
Joel □stblom ◽  
Nika Shakiba ◽  
Peter W. Zandstra
Keyword(s):  
Cell Fate ◽  
Reaction Diffusion ◽  
Positional Information ◽  
Periodic Patterns ◽  
Experimental Conditions ◽  
Radial Gradient ◽  
Biological Fate ◽  
Dependent Cell ◽  
Geometrically Constrained ◽  
High Throughput Assay

AbstractHow position dependent cell fate acquisition occurs during embryogenesis has been a central question in developmental biology. To study this process, we developed a defined, high-throughput assay using BMP4 to induce peri-gastrulation-like fate patterning in geometrically constrained human pluripotent stem cell colonies. We observed that, upon BMP4 treatment, phosphorylated SMAD1 (pSMAD1) activity in the colonies organized into a radial gradient – an observation mechanistically compliant with a BMP4-NOGGIN Reaction-Diffusion (RD) model. Consequent fate acquisition occurred as a function of both the pSMAD1 signaling strength, and induction time – consistent with the Positional-Information (PI) paradigm. Our findings implicate coordination between RD and PI underlying the peri-gastrulation-like fate patterning. This model not only predicts experimental results of perturbing key parameters like colony size, and BMP4 dose, but also identifies experimental conditions that rescue patterning in colonies of sizes that have been reported to be patterning-reticent, and recapitulate RD-like periodic patterns in large colonies.

scholarly journals Toxicity of chlordane at early developmental stage of zebrafish

2017 ◽  
Author(s):  
Jingxuan Xiong
Keyword(s):  
Early Stage ◽  
Real Life ◽  
Potential Effect ◽  
Early Developmental Stage ◽  
Dependent Manner ◽  
Lower Survival Rate ◽  
Zebrafish Larvae ◽  
Hatching Time ◽  
Early Developmental ◽  
Dose Dependent

AbstractChlordane is highly toxic organochlorine pesticides that have been widely used throughout the world for decades and posing adverse effects on the environment. Contents detected in tissue and blood samples have resulted in a raising concern for their potential effects on wildlife and humans. In this study, we investigate the potential effect of chlordane on the development of zebrafish embryos. Zebrafish larvae were treated with different concentrations (0, 25, 50, 100, 200 ng/L) of chlordane from 12 hours postfertilization (hpf). Different early stage parameters were observed at 1, 2, 3 and 4 day post-fertilization (dpf). Chlordane-exposed zebrafish larvae appeared significant lower survival rate, developmental and hatching time delay and decreased embryo productivity. The heartbeat rate and blood flow were decreased in a dose dependent manner. These results suggested that exposure to real life of chlordane led to direct morphological and phenotypic changes and effects systems related to development and reproduction even in short-term manner.

scholarly journals How Does a Tumor Get Its Shape? MicroRNAs Act as Morphogens at the Cancer Invasion Front

2020 ◽  
Vol 6 (2) ◽  
pp. 23 ◽  
Author(s):  
Catalin Vasilescu ◽  
Mihai Tanase ◽  
Dana Giza ◽  
Livia Procopiuc ◽  
Mihnea P. Dragomir ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Reaction Diffusion ◽  
Cancer Invasion ◽  
Target Cells ◽  
Invasion Front ◽  
Reaction Diffusion Model ◽  
Cancer Aggressiveness ◽  
Diagnosis Of Cancer ◽  
Front Shape ◽  
Dose Dependent

The generation and organization of the invasion front shape of neoplasms is an intriguing problem. The intimate mechanism is not yet understood, but the prevailing theory is that it represents an example of morphogenesis. Morphogenesis requires the presence of specific molecules, known as morphogens (activators and inhibitors), which can diffuse and elicit dose-dependent responses in their target cells. Due to their ability to modulate most of the coding transcriptome, their well-established role in embryogenesis, and their capacity to rapidly move between neighboring and distant cells, we propose microRNAs as inhibitors that could shape the cancer invasion front. In order to explain the genesis of the tumor border, we use Alan Turing’s reaction diffusion model, refined by Meinhardt and Gierer. This assumes the existence of an activator called a, and an inhibitor called h, which we hypothesize could be a freely moving microRNA. We used the fractal dimension as a measure of tumor border irregularity. We observed that the change in fractal dimension associates with variations in the diffusion coefficient of the activator (Da) or the inhibitor (Dh). We determined that the fractal dimension remains constant (i.e., the irregularity of the tumor border does not change) across a Dh interval, which becomes narrower as Da rises. We therefore conclude that a change in fractal dimension occurs when the balance between Da and Dh is disrupted. Biologically, this could be explained by a faulty distribution of the inhibitor caused by an abnormal density of the intercellular connection network. From a translational perspective, if experimentally confirmed, our observations can be used for a better diagnosis of cancer aggressiveness.

scholarly journals Spatially periodic calcium profiles around single channels

2016 ◽  
Author(s):  
S. L. Mironov
Keyword(s):  
Calcium Binding ◽  
Linear Models ◽  
Single Channel ◽  
Reaction Diffusion ◽  
Diffusion Problem ◽  
Cell Physiology ◽  
Single Channels ◽  
Periodic Patterns ◽  
Calcium Diffusion ◽  
Spatially Periodic

AbstractThe concept of calcium nanodomains established around the sites of calcium entry into the cell is fundamental for mechanistic consideration of key physiological responses. It stems from linear models of calcium diffusion from single channel into the cytoplasm, but is only valid for calcium increases smaller than the concentration of calcium-binding species. Recent experiments indicate much higher calcium levels in the vicinity of channel exit that should cause buffer saturation. I here derive explicit solutions of respective non-linear reaction-diffusion problem and found dichotomous solution - for small fluxes the steady state calcium profiles have quasi-exponential form, whereas in the case of buffer saturation calcium distributions show spatial periodicity. These non-trivial and novel spatial calcium profiles are supported by Monte-Carlo simulations. Imaging of 1D- and radial distributions around single α-synuclein channels measured in cell-free conditions supports the theory. I suggest that periodic patterns may arise under different physiological conditions and play specific role in cell physiology.

scholarly journals The people behind the papers – Andrew Economou and Jeremy Green

Development ◽  
2020 ◽  
Vol 147 (20) ◽  
pp. dev197293
Keyword(s):  
Developmental Biology ◽  
Perturbation Analysis ◽  
Reaction Diffusion ◽  
Biological Complexity ◽  
Periodic Patterns ◽  
Alan Turing ◽  
King's College ◽  
The People

ABSTRACTInteracting morphogens produce periodic patterns in developing tissues. Such patterning can be modelled as reaction-diffusion (RD) processes (as originally formulated by Alan Turing), and although these models have been developed and refined over the years, they often tend to oversimplify biological complexity by restricting the number of interacting morphogens. A new paper in Development reports how perturbation analysis can guide multi-morphogen modelling of the striped patterning the roof of the mouse mouth. To hear more about the story, we caught up with first author Andrew Economou and his former supervisor Jeremy Green, Professor of Developmental Biology at King's College, London.

scholarly journals High-throughput micro-patterning platform reveals Nodal-dependent dissection of peri-gastrulation-associated versus pre-neurulation associated fate patterning

2018 ◽  
Author(s):  
Mukul Tewary ◽  
Dominika Dziedzicka ◽  
Joel Ostblom ◽  
Laura Prochazka ◽  
Nika Shakiba ◽  
...  
Keyword(s):  
Reaction Diffusion ◽  
Positional Information ◽  
Significant Heterogeneity ◽  
Gene Profile ◽  
Self Organized ◽  
Micro Patterning ◽  
Post Implantation ◽  
Geometrically Confined

AbstractIn vitro models of post-implantation human development are valuable to the fields of regenerative medicine and developmental biology. Here, we report characterization of a robust in vitro platform that enabled high-content screening of multiple human pluripotent stem cell (hPSC) lines for their ability to undergo peri-gastrulation-like fate patterning upon BMP4 treatment of geometrically-confined colonies and observed significant heterogeneity in their differentiation propensities along a gastrulation associable and neuralization associable axis. This cell line associated heterogeneity was found to be attributable to endogenous nodal expression, with upregulation of Nodal correlated with expression of a gastrulation-associated gene profile, and Nodal downregulation correlated with a neurulation-associated gene profile expression. We harness this knowledge to establish a platform of pre-neurulation-like fate patterning in geometrically confined hPSC colonies that arises due to a stepwise activation of reaction-diffusion and positional-information. Our work identifies a Nodal signalling dependent switch in peri-gastrulation versus pre-neurulation-associated fate patterning in hPSC cells, provides a technology to robustly assay hPSC differentiation outcomes, and suggests conserved mechanisms of self-organized fate specification in differentiating epiblast and ectodermal tissues.

scholarly journals Study on the Formation of Complex Chemical Waveforms by Different Computational Methods

Processes ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 393
Author(s):  
Jiali Ai ◽  
Chi Zhai ◽  
Wei Sun
Keyword(s):  
Reaction Kinetics ◽  
Spiral Wave ◽  
Reaction Diffusion ◽  
Local Concentration ◽  
Periodic Patterns ◽  
Concentration Difference ◽  
Complex Chemical ◽  
Mass Transfer Theory ◽  
Chemical Waves ◽  
Oregonator Model

Chemical wave is a special phenomenon that presents periodic patterns in space-time domain, and the Belousov–Zhabotinsky (B-Z) reaction is the first well-known reaction-diffusion system that exhibits organized patterns out of a homogeneous environment. In this paper, the B-Z reaction kinetics is described by the Oregonator model, and formation and evolution of chemical waves are simulated based on this model. Two different simulation methods, partial differential equations (PDEs) and cellular automata (CA) are implemented to simulate the formation of chemical waveform patterns, i.e., target wave and spiral wave on a two-dimensional plane. For the PDEs method, reaction caused changes of molecules at different location are considered, as well as diffusion driven by local concentration difference. Specifically, a PDE model of the B-Z reaction is first established based on the B-Z reaction kinetics and mass transfer theory, and it is solved by a nine-point finite difference (FD) method to simulate the formation of chemical waves. The CA method is based on system theory, and interaction relations with the cells nearest neighbors are mainly concerned. By comparing these two different simulation strategies, mechanisms that cause the formation of complex chemical waves are explored, which provides a reference for the subsequent research on complex systems.

Sign in / Sign up

Export Citation Format

Share Document