Although the mechanism is still not fully understood, the institute's scientists discovered that during the construction of the cell skeleton, the fibers tend to the same side, causing the skeleton to be built as a coil. This twist is due to the interrelationship between two types of fibers, which are built perpendicular to each other.
The two sides of our body are not equal: the left lobe and the right lobe of the brain perform different functions, the heart lies to the left of the center of the body, and more. How is this asymmetry created during fetal development? The scientists of the Weizmann Institute of Science discovered that cells know how to distinguish between right and left using a "compass" capable of pointing in a certain direction already at the level of the individual cells.
A research group, led by Prof. Alexander Bershadsky from the Department of Molecular Biology of the Cell at the institute, examined the self-organization of the cell skeleton - a system of protein fibers that keep the cell intact. This skeleton changes its shape frequently, when the cell, after division, adheres to the intercellular pattern. These changes affect the formation of contact points, which play an important role in the movement of the cell and its communication with the environment.
To examine how the cell skeleton organizes itself when these contact points are formed, Dr. Yeh-Han Ti, and other scientists from Prof. Bershadsky's group at the Institute of Mechanobiology of the National University of Singapore, used an innovative approach, by which they observed the skeleton of a single cell , without disruption of cell movement. The scientists made the cells adhere to round "disks" with a diameter of a single cell, that is, less than 0.05 They marked the actin fibers, the protein that is the main component of the cell skeleton, and observed how clusters of these fibers grew from the edges of the cell towards its center, until a pattern resembling the spokes of a bicycle wheel was formed. The scientists discovered that the symmetry of the actin "spokes" always breaks in the same direction , so that all the fibers tend to the same side, and cause the growing cell skeleton to rotate counter-clockwise - until the formation of coil
The forces exerted on the actin fibers
To explain this process, Prof. Tom Shemesh, then a post-doctoral researcher at the Weizmann Institute of Science and now a researcher at the Technion, in collaboration with Prof. Michael Kozlov from Tel Aviv University, built a mathematical model that calculated the mechanical properties of the actin fibers, and the forces exerted on them during the construction of a skeleton the cell Scientists from the University of Michigan and the Sanford-Burnham Medical Research Institute in California participated in this study.
The model successfully predicted the dynamics of the formation of the cytoskeleton, and revealed that the rotation of the cytoskeleton results from the connection between two types of fibers, which are built perpendicular to each other, like a spider's web. During the interaction between the two types of fibers the "spokes of the wheel" tend to the left. The tilt increases as the fibers interact with each other, like falling dominoes, eventually causing the skeleton to collapse into a coil.
But why does the skeleton always turn in the same direction? The model showed that since each actin fiber has the shape of a right-handed helix whose end is held in place, it should rotate around its axis while the cytoskeleton
Organizes - just as it happened in the experiment. Thus, the asymmetry of a single protein translates into the asymmetry in the behavior of the entire cell. These findings may help - in the future - in the development of tissue engineering and wound healing.
- Previous articles on the subject:
- parent holdings
- The triangle of forces
- Looking in the jar
