Scientists have discovered a cell structure called “the mesh” that helps hold cells together.
The discovery, which has been published in the journal eLife, changes our understanding of the cell’s internal scaffolding.
The findings also have implications for researchers’ understanding of cancer cells because the mesh is partly made of a protein which is found to change in certain cancers, such as those of the breast and bladder.
“As a cell biologist you dream of finding a new structure in cells but it’s so unlikely. Scientists have been looking at cells since the 17th century and so to find something that no one has seen before is amazing,” says Stephen Royle, associate professor and senior Cancer Research UK Fellow at the division of biomedical cell biology at Warwick Medical School.
Watching the mitotic spindles
The team made the discovery by accident while looking at gaps between microtubules that are part of the cells’ “internal skeleton.” In dividing cells, these gaps are incredibly small at just 25 nanometers wide—3,000 times thinner than a human hair.
One of Royle’s PhD students was examining structures called mitotic spindles in dividing cells using a technique called tomography which is like a hospital CAT scan but on a much smaller scale. This meant that they could see the structure that they later named the mesh.
Mitotic spindles are the cell’s way of making sure that when they divide each new cell has a complete genome. Mitotic spindles are made of microtubules and the mesh holds the microtubules together, providing support. While “inter-microtubule bridges” in the mitotic spindle had been seen before, the researchers were the first to view the mesh.
“We had been looking in 2D and this gave the impression that ‘bridges’ linked microtubules together,” says Royle. “This had been known since the 1970s. All of a sudden, tilting the fiber in 3D showed us that the bridges were not single struts at all but a web-like structure linking all the microtubules together.”
Cancer research and chromosomes
The discovery could affect research on cancerous cells. A cell needs to share chromosomes accurately when it divides otherwise the two new cells can end up with the wrong number of chromosomes. This is called aneuploidy and this has been linked to a range of tumors in different body organs.
The mitotic spindle is responsible for sharing the chromosomes and the researchers believe that the mesh is needed to give structural support. Too little support from the mesh and the spindle will be too weak to work properly, however too much support will result in it being unable to correct mistakes.
The team found that one of the proteins that make up the mesh, TACC3, is over-produced in certain cancers. When this situation was mimicked in the lab, the mesh and microtubules were altered and cells had trouble sharing chromosomes during division.
“Problems in cell division are common in cancer—cells frequently end up with the wrong number of chromosomes,” says Emma Smith, senior science communications officer at Cancer Research UK.
“This early research provides the first glimpse of a structure that helps share out a cell’s chromosomes correctly when it divides, and it might be a crucial insight into why this process becomes faulty in cancer and whether drugs could be developed to stop it from happening.”
The study received funding and support from Cancer Research UK and North West Cancer Research.
Source: University of Warwick