Seeing cilia: Lighting the dark

Cilia are small hair-like projections found on most mammalian cells, when they are not dividing, and there is a lot of scientific interest in their roles in cell communication and movement of substances past the cell. But cilia are very small and hard to visualize, especially in living mammalian tissue.

Researchers from University of Alabama at Birmingham Medical School have tagged a protein component of cilia with GFP in order to make them visible not just on slides but in a live animal so their natural behavior can be recorded.

In the brain, primary cilia could be seen in the hippocampus, and motile cilia in the ventricles and the choroid plexus, where cerebrospinal fluid is made, presumably to aid movement of fluid in these areas. Cilia were also found in the retina of the eye where they are needed for reception of light.

Cilia were observed in the kidneys of live mice and, using video recording, they could be seen to bend in the direction of fluid movement along the tubule. With reduced fluid movement in the tubule, the cilia are frequently observed waving back and forth. This is most likely passive, caused by glomerular filtration, as kidney cells do not appear to have the machinery necessary for cilia movement.

Dr Bradley Yoder, who led this study, explained, "By tagging cilia we can now easily see the behavior of cilia in as natural an environment as possible. This will vastly aid research into ciliopathies, disorders of cilia, which can have serious consequences during development and for health."