Elizabeth Smith's Lab at Dartmouth College  



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Cilia and flagella are found on diverse cell types including sperm cells of vertebrates and some invertebrates, unicellular protozoa, and several vertebrate epithelial cell types. In mammals, for example, motile cilia found on cells lining the brain ventricles circulate cerebrospinal fluid; cilia in the respiratory tract sweep debris from the lungs; and oviduct cilia move the fertilized egg to the uterus. In addition, epithelial cilia present early in development are involved in left-right axis determination. Some epithelial cells, such as retinal photoreceptor cells and certain renal epithelial cells, possess immotile cilia which we now know play important sensory roles in cell function. Individuals with motility impaired cilia / flagella or defects in ciliary / flagellar assembly may have any number of serious disorders including hydrocephaly, retinal degeneration, respiratory distress, polycystic kidney disease, and infertility.

We are interested in understanding the complex regulatory cues that modulate ciliary beating. The motility of these organelles requires the precise regulation of at least four different dynein motor complexes. This regulation is mediated in part by a signal transduction pathway that includes second messengers, as well as kinases and phosphatases anchored to the axoneme. Our goal is to understand how these signal transduction pathways are integrated to produce the complex waveforms typical of beating cilia. We use the biflagellate green alga Chlamydomonas reinhardtii as a model system. Virtually all of the genes in which mutations result in human disease were first identified in Chlamydomonas. Our research is funded by the National Institutes of Health.  

Chlamydomonas flagella for wild-type cells beat at approximately 60hz. This video was made using high speed photography. Images were captured at 500fps and are played back at approximately 5fps.