January 13, 2021
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Adrian Jacobo, PhD
The Rockefeller University, New York, NY
"Symmetry breaking during morphogenesis of a mechanosensory organ"
The development of mechanosensory epithelia, such as those of the auditory and vestibular systems, results in the precise orientation of mechanosensory hair cells and consequently directional sensitivity. After division of a precursor cell in the zebrafish lateral line, the daughter hair cells differentiate with opposite mechanical sensitivity. This process produces neuromasts containing equal numbers of hair cells of two opposite polarities, half of them sensitive to caudad water movement and half to rostrad flow.
Using a combination of experimental tools and mathematical modeling we show how Notch-mediated lateral inhibition produces a bistable switch that reliably gives rise to hair-cell pairs of opposite polarity. This spontaneous symmetry breaking drives polarity-dependent movements of hair cells that lead to the establishment of a mirror-symmetric organization of the organ. We model these reconfigurations by describing the effective surface tensions of the hair cells and the changes in these quantities throughout the developmental process. These results provide a unified experimental and theoretical framework to describe the polarity selection and directed migration of hair cells in the zebrafish lateral line.