A new study demonstrates the dynamic role cilia play in guiding the migration of neurons in the embryonic brain. Cilia are tiny hair-like structures on the surfaces of cells, but here they are acting more like radio antennae. In developing mouse embryos, researchers were able to see cilia extending and retracting as neurons migrate. The cilia appear to be receiving signals needed for neurons to find their places. Genetic mutations that cause the neurodevelopmental disorder Joubert syndrome interfere with these migratory functions of cilia, the researchers show. The finding suggests that problems with neuron migration may explain some aspects of Joubert syndrome patients' symptoms. The results were published November 13, 2012 in the journal Developmental Cell. "The most surprising thing was how dynamic the cilia are," says Tamara Caspary, Ph.D., assistant professor of human genetics at Emory University School of Medicine. "As interneurons migrate into the developing cerebral cortex, they move in steps. When they pause, we could see the cilia extending, as if the interneurons are trying to figure out where to go next." The paper is the result of a collaboration between Dr. Caspary's laboratory and that of Eva Anton, Ph.D., professor of cell and molecular physiology at the University of North Carolina School of Medicine. First author Dr. Holden Higginbotham, formerly a postdoc in Anton's laboratory, is now a faculty member at Brigham Young University in Idaho. Readers may be familiar with motile cilia, which can be found on a paramecium or in our trachea or reproductive organs. In contrast, primary (non-motile) cilia can be found on almost every cell in the human body, each cell having just one. Ciliopathies are a class of genetic disorders involving defects in cilia, and include kidney and eye diseases, as well as Joubert syndrome.
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