Imagine sitting in a meeting where the shape of the table and your place at it could impact how well you get along with other members. Cells also communicate with their closest neighbors, and in embryos, nothing is left to chance in the “plan of placement” of the first cells. However, questions remain about how this process is controlled and how it can influence the overall growth of an organism.
Building on their previous studies of worm egg development, researchers from Kyoto University’s Kanagawa Institute of Technology and the National Institute of Genetics have now accurately modeled the shape of worm eggshells. eggs to show how the space in the egg and the contours of the shell direct the relative positions of cells in the growing embryo. Their findings may provide a theoretical basis for directing stem cell development into larger tissues and organs.
Lead author Professor Sungrim Seirin-Lee of the Institute for Advanced Study of Human Biology (WPI-ASHBi) at Kyoto University said: “We found that when Caenorhabditis elegans the embryos have reached the 4-cell stage, there are five patterns that the cells arrange in the spaces of the egg. But the inverse T-arrangements we found did not match our previous calculations based on cell attraction and egg aspect ratio. We realized that something was missing from our model.”
Looking at the eggs of the worm under a microscope Caenorhabditis elegans, the team previously noticed that in longer-shaped eggs, the first four cells arranged in a line; on the contrary, if the shell were round, the cells would group together. They also identified an unexplained “reverse-T” pattern in some eggs, where three cells cluster together, creating a T-shaped space, with one cell lined up at the end.
The team hypothesized that the formation of this pattern could be controlled by variations in eggshell contours. To test this, they applied a more sophisticated ‘phase field’ mathematical model that could more accurately account for the actual egg shape measured from the worms. This new model has successfully reproduced the previous results and now also accounts for the unexplained inverse-T arrangement. The results show for the first time that previously overlooked local egg contours affect cellular patterns.
In the new way of looking at the embryo, it turns out that it is actually “the space inside the egg” that is a key factor that determines cell patterns. To further test this concept, the researchers looked at worm eggs that were genetically modified to allow more space for the cells inside. With more space, the first four cells preferred to spread out in a line rather than group together.
Seirin-Lee said: “Worm eggshells are often treated as a simple oval shape, but the actual shape may be closer to a capsule in some cases. We now understand how geometric constraints and l “Space is important for directing cells, and this concept also applies to human cells. We hope that this work will lead us to a better understanding of artificially controlled cell differentiation and extend the capabilities of stem cell techniques.”
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Material provided by Kyoto University. Note: Content may be edited for style and length.