Microvilli Management

What am I looking at?

This is a video of a kidney epithelial cell in culture. You can see the purple microvilli being created with the assistance of the green actin cross-linking proteins; these proteins connect actin filaments within a cell.

Biology in the background

Actin proteins assemble into helical filaments (one of three types of cytoplasmic filaments known collectively as microfilaments), which form a network distributed through eukaryotic cells. These actin filaments play an important role in giving cells their structure, enabling cells to move, and allowing the formation of specialized structures. Actin cross-linking proteins bind the actin filaments together, helping them maintain their structure and, in conjunction with other proteins, helping them exert force on the cell membrane from inside the cell. This force allows the actin filaments to push the cell membrane outward and form long, thin structures like microvilli.

In this video, you can see collections of green actin cross-linking proteins condensed so much that it looks almost white where new microvilli are being formed. These white fibers then turn purple, now marking a protein present only in mature microvilli.

A microvillus is about 1 micrometer long, or roughly 100 times smaller than the width of a human hair, and an actin cross-linking protein is about 35 nanometers long, or roughly 3,000 times smaller than the width of a human hair.

Technique

This video was created using confocal microscopy.