In an IBioBA’s paper published in the journal Frontiers in Physics, the Information Processing in Cells and Tissues group provides
new insights into the development of the zebrafish spine.
It is known that we come from the union between a female and a male cell. However, there is still much to be known about how, from the division of that first cell, continues the embryonic development that will give rise to the different parts of an organism.
The vertebrate axis, for example, is segmented into repetitive structures: the vertebres. It has been known for some time that there is a biological clock, known as the segmentation clock, that keeps the pulse of the development of the different repetitive segments that form a vertebrate, such as the vertebral column, and the other parts of the body that are formed in this way.
In a paper published in Frontiers in Physics, Sol Fernández Arancibia, who recently obtained her PhD, proposes a mathematical model to describe the segmentation pattern of the notochord, the embryonic tissue that will later become the center of the zebrafish’s axis.
The pillars of the work
The research was based on a previous publication by Luis Morelli, PhD in Physics and head of the Information Processing in Cells and Tissues research group, in which, together with German colleagues, he described how the system that regulates the development of the spine works and what role the notochord plays during this process. They observed, among other issues, that “the notochord develops with a mechanism that is independent of the clock, but that somehow when it is functioning it receives instructions from the adjacent tissue (somites), which was previously segmented”, explains the researcher.
“Initially it was believed that the whole vertebral structure was controlled entirely by the segmentation clock and the somites”, adds Fernández Arancibia. But thanks to that work, an autonomous patterning mechanism was discovered in the zebrafish notochord, which is sequentially established and progresses from the head to the tail (from front to back).
Using this basic knowledge, and with the intention of resolving some questions that had been left unexplained in that paper, Sol proposed a reaction-diffusion wavefront theory to describe the development of the zebrafish notochord.
About the reaction-diffusion wavefront
Fernández Arancibia then set to work to elucidate how sequential segmentation occurred in the presence of the noise and fluctuations present in gene expression. “Because genes are never completely on or off -says Morelli- there can be random perturbations (such as small ‘sparks’) that cause them to be expressed to a greater or lesser extent”.
For this, she designed a mathematical model where the pattern is generated by a reaction-diffusion mechanism between an activator and an inhibitor. “The name of the theory is due to the fact that we propose the existence of a front that “ignites” the biochemical reactions between the activator and the inhibitor, as it advances from the upstream to the downstream zone”, explains Sol.
The influence of the pattern previously formed by the somites was also included in the model as a spatial information profile that affects the inhibitor. In this way, Sol studied the various components of the new model, especially in relation to how noise and fluctuations can lead to defects in the segment patterns being formed.
“Through the work, we showed that this reaction wavefront ensures that a pattern is formed sequentially, in register with the signals, despite the presence of fluctuations. In addition, we saw that the speed and shape of the reaction wavefront can modulate the prevalence of defective patterns”, says Morelli.
In summary, “this work presents a mathematical model that allows describing experimental observations of zebrafish embryonic development, and at the same time provides a tool to generate new predictions that motivate future experiments”, concludes Fernández Arancibia.