Cilia are microtubule based cellular projections that serve a wide variety of essential functions in animal cells. Defects in cilia structure or function have recently emerged as etiological mechanisms underpinning diverse human diseases. While many eukaryotic cells possess only one or two cilia, some cells, including those of many unicellular organisms, exhibit extensive multiciliation. In vertebrates, multiciliated cells (MCCs) 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 MCCs is associated with diseases of the brain, airway and reproductive tracts. Despite their importance, MCCs are relatively poorly studied and we are only beginning to understand the mechanisms underlying their development and function. Here, we briefly review the general phylogeny and physiology of multiciliation and detail our current understanding of the developmental and cellular events underlying the formation, maturation, and function of MCCs in vertebrates.

The mechanisms linking systems-level programs of gene expression to discrete cell biological processes in vivo remain poorly understood. In this study, we have defined such a program for multi-ciliated epithelial cells (MCCs), a cell type critical for proper development and homeostasis of the airway, brain and reproductive tracts. Starting from genomic analysis of the cilia-associated transcription factor Rfx2, we used bioinformatics and in vivo cell biological approaches to gain insights into the molecular basis of cilia assembly and function. Moreover, we discovered a previously un-recognized role for an Rfx factor in cell movement, finding that Rfx2 cell-autonomously controls apical surface expansion in nascent MCCs. Thus, Rfx2 coordinates multiple, distinct gene expression programs in MCCs, regulating genes that control cell movement, ciliogenesis, and cilia function. As such, the work serves as a paradigm for understanding genomic control of cell biological processes that span from early cell morphogenetic events to terminally differentiated cellular functions.DOI: http://dx.doi.org/10.7554/eLife.01439.001

The planar cell polarity effector Fuz is required for normal particle dynamics of the intraflagellar transport system, specifically in the retrograde transport of proteins.