Pressured into making a kidney

Developmental biologists spend a great deal of time studying molecular signals that determine the when and where of organogenesis. But recent results indicate they may be overlooking something. Mechanical forces provided by the vasculature are also at work, according to a new study by Fabrizio Serluca, Ian Drummond, and Mark Fishman (Harvard Medical School, Boston, MA), who examine the development of the zebrafish kidney glomerulus.

The glomerulus is made up of unique layers of vessel endothelium that filter fluid from the blood without removing proteins or cells. Fluid flows between the endothelial cells, before moving sequentially through the basement membrane of the kidney and epithelial cells known as podocytes, and finally into the tubules of the kidney. During zebrafish embryogenesis, the podocytes form the glomerulus by migrating and coalescing to an area surrounding a vessel...