About this Research Topic
Ciliates have been intensively studied for well over 100 years as motile cells that respond in obvious ways to their environment. Their motility is based in ciliary beating that moves the cells around in their watery environs whether as a free-swimming cell or one crawling on the substratum. Therefore, their swimming (forward, reverse and turn) is a read out of their ciliary function. The early studies of behavior were taken further with the use of microelectrodes to record from the cells and thereby develop the original picture of the cilia as sensory organelles. It became clear that ion channels in the ciliary membrane were responsible for modifying the beating of the cilia that, in turn, controlled the swimming behavior of the cells. This enormously important development was quickly augmented with the application of genetics and the search for mutants in order to our understanding the ciliary motility.
There has been a 21st century renaissance in the interest in cilia after the connection between primary cilia and the diseases called ciliopathies was established. Ciliates are generally equipped with motile cilia, which serve as a model system for vertebrate and other motile cilia like lung cilia. However, the high conservation of the basic proteins, structural parts of the cilia like axonemes, transport systems for cilia construction, and sensory components makes it difficult to divide the world into motile vs primary-immotile cilia. This conservation allows ciliates to make important contributions to our understanding of cilia in general.
Ciliates, endowed with thousands of cilia that can be harvested or studied in situ, and present an advantage over cells with only single primary cilia for many kinds of investigations. Ciliates provide a wealth of proteins, lipids, sensory molecules for analysis by many cutting-edge techniques. Whole genome sequencing is regularly used to identify new mutants; mass spectrometry is routinely used in combination with biochemical studies; cryo-electron tomography and super resolution microscopy are yielding new information about the structure of the axonemes, transition zones, ends of the cilia and more.
Another important contribution that ciliates make is the advantage of identifying subtle changes in cilia and their associated proteins by looking at the surface patterns that can be models for multiciliated vertebrate cells. The patterns when disrupted are immediately obvious and allow for investigations into proteins and genes that cause less than catastrophic loss of cilia when disturbed.
This Research Topic will describe the most modern approaches to cilia biology using ciliates as model systems.