Each of the cells lining our intestines is covered with a densely packed array of bristle-like projections known as the brush border (pictured). By increasing the surface area of the cell membrane, this microscopic shag pile carpet enhances nutrient absorption. It also defends against pathogens. Despite its importance, however, scientists know little about how the brush border is formed. Now, with the help of a powerful microscope, they’ve shown that as the bristles grow, they attach to each other at the tips with thread-like links. This is how they stay tightly packed. And the researchers have discovered that a protein called harmonin plays a key role in establishing these connections: in mice missing the protein, the brush border was poorly formed in parts of the intestine. The results could explain why people with Usher syndrome, a form of inherited deafness associated with abnormal harmonin, suffer with a mysterious gastro-intestinal disease.
Written by Daniel Cossins
BPoD is also available in Catalan at www.bpod.cat with translations by the University of Valencia.