Cell Division Going Off the Rails

What am I looking at?

This is a video of a HeLa cell as it undergoes an incomplete round of cell division. In this video, the actin protein is labeled in black and red, and you can see an actin wave traveling around the periphery of the cell just before the cell begins to split. The DNA can be seen as lighter gray spots in the center of the cell.

Biology in the background

Cell division is the process of one cell splitting into two nearly identical daughter cells. It is essential for the nuclear DNA to be split equally during this process, or neither daughter cell will function correctly and may not survive.

This video shows a cell undergoing the last stages of cell division, but the DNA does not split equally, which triggers a form of programmed cell death called apoptosis. Bulges in a cell membrane, called blebs, are a hallmark of apoptosis – distinguishing it from necrosis, which is accidental cell death. Blebbing is a controlled process, involving specific cellular mechanisms, including cytoskeletal rearrangement. Blebs form apoptotic bodies, containing most of a cell’s cytoplasm and organelles, which aid in the dying cell’s clearance by the immune system. Necrosis, on the other hand, is much messier – the cell breaks up, releases its contents, and triggers an inflammatory response.

The reason this cell did not divide properly is because it was under the laser microscope too long and so was damaged by what researchers call phototoxicity. The intensity of the lasers on advanced microscopes is very high, and cells can survive only so long under their glare.

A HeLa cell can range from 20 micrometers to 40 micrometers across, or roughly a quarter to half the width of a human hair, while actin filaments are tiny – only about 7 nanometers wide, or roughly 10,000 times smaller than the width of a human hair.

Technique

This video was created using confocal microscopy.