The 9 + 2 Axoneme Anchors Multiple Inner Arm Dyneins and a Network of Kinases and Phosphatases That Control Motility

Cilia and flagella are found on a variety of cell types, ranging from single cell protozoa and sperm to the ciliated epithelia of the respiratory and reproductive tracts. Despite this diversity, most motile cilia and flagella contain a highly ordered structure, the 9 2 axoneme (Fig. Ciliary motility is generated by the dynein-driven sliding of outer doublet microtubules. Defects in the dynein motors or components that regulate their activity can have profound consequences; in vertebrates, these include infertility, respiratory disease, and defects in the determination of the left-right axis during embryonic development The biochemical complexity of the organelle has made it challenging to identify the relevant loci by traditional mapping methods However, significant progress is being made using candidate genes identified in model organisms. For instance, it is much simpler to analyze mutations affecting flagellar motility in Chlamydomonas using biochemical, structural, and molecular approaches (Fig.