Filopodia (also microspikes) are slender
cytoplasmic projections that extend beyond the leading edge of
lamellipodia in migrating cells. They contain actin filaments cross-linked into bundles by actin-binding proteins, e.g.
fascin and
fimbrin. Filopodia form focal adhesions with the substratum, linking it to the cell surface. Many types of migrating
cells display filopodia, which are thought to be involved in both sensation of chemotropic cues, and resulting changes in directed locomotion.