Biology of Cilia and Ciliopathies

Cilia and flagella are microtubule-based appendages extending from the basal body of most eukaryotic cells, and are classified as either motile or primary. Motile cilia or flagella can be found on many cells such as Chlamydomonas, sperm, and respiratory tract epithelial cells. This type of cilia is responsible for movement of the cell itself or generation of fluid flow. In contrast, primary cilia are non-motile organelles that are critically involved in visual, olfactory and auditory signal transduction and play key roles in the regulation of gene expression, development, and behavior. This chapter reviews the current understanding of the various mechanisms involved in cilia and flagellar assembly and maintenance. Consistent with the nearly ubiquitous cellular distribution, cilia have been implicated in numerous human diseases collectively known as ciliopathies. This chapter also discusses several major ciliopathies including primary ciliary dyskinesia, hydrocephalus, polycystic kidney disease, Bardet-Biedl syndrome, and cancer.