Cell Division on Fire

What am I looking at?

This is a time-lapse video showing the dynamic nature of the ER in monkey kidney cells as they undergo cell division. The density of the ER network is represented by the brightness of the orange color. The less dense the ER network, the darker the orange color, and the denser the network, the lighter the orange color; at its most dense, it’s almost white.

Biology in the background

The ER is the protein synthesis and processing center of a cell, and some lipids are also synthetized within its lumen, or interior. There are two types of ER in a cell: rough ER and smooth ER. The rough ER membrane is studded with ribosomes, where proteins are synthesized. The smooth ER is where some lipids, phospholipids, and steroids are synthesized and some protein folding and processing occur. The rough ER is composed of an interconnected network of flattened, membrane-enclosed sacs known as cisternae. The smooth ER has a more interconnected tubular structure. Together, the rough and smooth ER form a single continuous membrane network extending throughout a cell’s cytoplasm.

During cell division, the ER condenses around the nucleus as the cell’s chromatin – a complex of DNA and proteins – is packed into the chromosomes. Then, as the cell gets ready to divide, this condensed version of the ER begins to accumulate on both sides of the cell. This ensures that once the cell splits, each of the daughter cells gets at least some ER from the parent cell. As the new cells move back to their baseline state, a stage known as interphase, the ER expands again and resumes its function.

This type of monkey kidney cell has a diameter of about 20 to 25 micrometers, or roughly three times smaller than the width of a human hair.

Technique

This video was created using confocal microscopy.