The Tips of Microtubules

What am I looking at?

This is a time-lapse video demonstrating the dynamic nature of microtubules in a monkey kidney cell that’s been cultured in a dish. The growing ends of the microtubules are red/orange, marked by a fluorescent protein called EB3 that binds the growing tips of the microtubules. The blue background of the cell is a fluorescently marked protein that labels the lumen, or interior, of the endoplasmic reticulum.

Biology in the background

Microtubules are composed of a protein called tubulin, which consists of alpha and beta subunits that assemble into large, tube-shaped filaments within the cell. These fibers are dynamic, growing from one end and shrinking from the other end whenever they need to dissolve or move. The end that grows is known as the positive end, and the specialized proteins that assist in this growth are collectively called plus-end-tracking proteins, or +TIPs. The EB3 marker binds to these +TIPs and contains a fluorescent tag – which allows researchers to visualize the microtubules’ growing ends as they radiate from a central structure called the centrosome.

A microtubule is about 25 nanometers in diameter, or roughly 3,000 times smaller than the width of a human hair.

Technique

This video was created using confocal microscopy.