Multiciliated cells.

Cilia are microtubule-based projections that serve a wide variety of essential functions in animal cells. Defects in cilia structure or function have recently been found to underlie diverse human diseases. While many eukaryotic cells possess only one or two cilia, some cells, including those of many unicellular organisms, exhibit many cilia. In vertebrates, multiciliated cells are a specialized population of post-mitotic cells decorated with dozens of motile cilia that beat in a polarized and synchronized fashion to drive directed fluid flow across an epithelium. Dysfunction of human multiciliated cells is associated with diseases of the brain, airway and reproductive tracts. Despite their importance, multiciliated cells are relatively poorly studied and we are only beginning to understand the mechanisms underlying their development and function. Here, we review the general phylogeny and physiology of multiciliation and detail our current understanding of the developmental and cellular events underlying the specification, differentiation and function of multiciliated cells in vertebrates.