ABSTRACT
This chapter describes the long history of the discovery of the primary cilium, an organelle that has major biomedical ramifications as there are over 100 different diseases known as ciliopathies where primary cilia biogenesis and/or function are impaired. The chapter begins with early observations of cilia by Dutch microscopist Antoni van Leeuwenhoek in the seventeenth century and then details the finding that some cells have a single, primary, and non-motile cilium. There is emphasis on the reluctance of scientists to let go of the notion that the primary cilium is a non-motile organelle unlike other cilia, and there is discussion of the Lenhossek–Henneguy hypothesis that maintains that the primary cilium is derived from the centrosome and that a ciliated cell can therefore not undergo cell division when its centrosome is engaged in ciliogenesis. Also addressed within this chapter is the revolution in understanding primary ciliary function as a key signaling organelle over the last 20 years.
