Note that podosomes can be distinguished from other F-actin-rich structures or from other matrix contacts. For example, focal adhesions and focal contacts do not display a core structure of F-actin. Unlike focal adhesions, podosome assembly does not require de novo protein synthesis. However, most of the podosome ring components are found in focal adhesions and other cell-matrix contacts. Podosomes are typically found in cells that cross tissue boundaries, recruited to the leading edge of migrating cells, and are often sites of extracellular matrix degradation.