The rods and cones in our retinas detect light. Thankfully, amazing cameras do the same and have captured images of these photoreceptor cells in today’s image.
The outer segments of photoreceptor cells are modified cilia that detect light at the back of the eye. Like the cilia in many other cell types, these outer segments can’t synthesize their own proteins but instead depend on transport of proteins from the cell body along ciliary microtubules. IFT proteins (intraflagellar transport) are important for this transport of material, and a recent paper describes the roles of the IFT20 protein in the retina. IFT20 is required for transport into the outer segments and is uniquely localized to the Golgi complex. Keady and colleagues conclude that IFT20 functions both as part of and independently of the typical IFT system. Images above show retinal sections of mice with normal IFT20 (top) and IFT20 mutated in cone cells (bottom). The lack of RG opsin (green) in IFT20 mutants indicates an absence of cone cells, while normal rhodopsin staining (red) indicates that rod cells are unaffected in mutants.
Keady, B., Le, Y., & Pazour, G. (2011). IFT20 is required for opsin trafficking and photoreceptor outer segment development Molecular Biology of the Cell, 22 (7), 921-930 DOI: 10.1091/mbc.E10-09-0792