Researchers have pinpointed the molecular cause of a rare genetic disease in humans called Bardet-Biedl syndrome, or BBS. People with the disorder suffer from obesity, retinal degeneration, kidney cysts and polydactyly (having extra fingers or toes). Specifically, the researchers have discovered that genetic mutations associated with the disease affect a protein complex that ferries receptors and other proteins from the cell's membrane to the surface of the primary cilium.