The division of human cells may not exactly align with what’s written in textbooks
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Scientists have discovered a kind of division that allows cells to use the information encoded in their shape to direct what kinds of cells their offspring become. This could help us develop ways of engineering tissues and deepen our understanding of how cancers spread.
Until now, scientists thought that most cells in the body become round as they prepare to divide in two. This makes it easier for them to distribute their contents equally between their “daughter” cells, resulting in two cells of the same type.
An exception to this is stem cells, which undergo an unequal, or asymmetric, cell division, which produces cells of two different types.
But Shane Herbert at the University of Manchester, UK, and his colleagues noticed that non-stem cells in the developing blood vessels of zebrafish embryos were also dividing asymmetrically. These cells, known as endothelial cells, were migrating to form new blood vessel branches and divided without rounding to create two different types.
When the team manipulated the shape of human endothelial cells in a lab dish, it confirmed that their shape before division predicted how symmetric that division was going to be. Longer, thinner cells were the most likely to divide asymmetrically, which suggests that cells can fine-tune the nature of their divisions depending on the shape they take between them.
It means cells don’t lose information about their structure and behaviour as they would if they underwent rounding, says Herbert. “Very frequently, they actually retain their shape, and that means they can transfer that kind of memory.”
This also means that cells don’t have to stop what they are doing to divide, but can migrate, divide and generate different cell types all at once. This lets them respond quickly to the dynamic demands of development, such as the need to supply an expanding tissue with blood vessels or nerves.
The discovery could have applications for growing replacement tissues in the lab, where the ability to grow blood vessels is a key limitation. “Our work is showing is that there’s a really specific environment that’s needed to give these cells the kind of shape and behaviour that they need to generate functional blood vessels,” says team member Holly Lovegrove, also at the University of Manchester. Manipulating cell shapes could offer a new way to generate certain cell types, she says. Cancer, meanwhile, spreads by generating clusters of migrating cells, so the new findings could provide further insight into how they do this.
It is a nice example of how organisms can tweak mechanisms like cell rounding to do different things, such as the multitasking needed to sculpt developing tissues, says Buzz Baum of the MRC Laboratory of Molecular Biology in Cambridge, UK. “It’s a clever way to keep the information you need while still growing the network by making more cells.”
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