Ah, cells! We have them in our body and we know they do many wonders for us, but we never thought we would need to worry about them staying in shape. However, a new study has revealed that cells need to keep their shape and proportions to successfully reproduce through cell division.
The novel and rather amusing research comes from the Francis Crick Institute and King's College London. It turns out that cells, all of them from the single ones to the more complex, keep their proportions as they grow or shrink.
Why you might ask? Well, it is actually so they can split in the middle, but the correct middle! To reproduce through cell division, cells need to make a copy of their DNA and then split into two right in the middle. (We said middle a lot, but it's important here).
And it turns out that to find that so important correct middle, the cells need to maintain their original shape. The revelation was made by studying yeast cells from the related S. japonicus and S. pombe species.
These yeast cells are pill-shaped and essentially have tips that send molecular signals which meet in the right middle. If the cell shape is distorted by becoming too round, then the ends' signals get mixed up.
This has destructive consequences such as either tearing the DNA and killing off the cell or leaving two copies of DNA in only one cell while the other remains empty.
"If a division leaves two copies of DNA in one cell, the one without DNA will die and the one with two copies is likely to have problems when it next divides, which in human cells can lead to cancer," explained Professor Snezhka Oliferenko, research group leader at the Crick and King's.
"To avoid this, it's vital that the division happens in the right place. We found that a cell's shape determines where it will divide, highlighting the crucial function of scaling at the cellular level. This helps to answer the fundamental evolutionary question of why and how organisms would evolve the ability to scale when their size changes."
And diet does matter! When these pill-shaped yeast cells are fed a restricted diet, they successfully manage to shrink to conserve nutrients when they divide.
"We found that S. japonicus relies on a gene called rga4 to regulate growth so the cell keeps its shape when it shrinks," said lead author Dr Ying Gu, postdoc in Snezhka's lab. "The cells simply divided into thinner cells of the same shape, which were able to live and multiply as normal."
The researcher also identified that when the rga4 gene was disabled, cells grew too much and divided wrong. "As long as the length-to-width aspect ratio is correct, S. japonicus can accurately divide in the middle and continue to thrive," says Snezhka.
"It's a beautiful organism to study, as it allows us to test fundamental biological principles and get clear, elegant results. We can ask questions like 'What's the point in scaling?', 'Why does cell shape matter?' and many more. By studying the similarities and differences between S. japonicus and sister species like S. pombe, we can gain insights into processes that are fundamental to life itself."
The study is published in Nature Communications.