The orientation of hair bundles on top of sensory hair cells (HCs) in neuromasts of the lateral line system allows fish to detect direction of water flow. Each neuromast shows hair bundles arranged in two opposing directions and each afferent neuron only innervate HCs of the same orientation. In previous paper, we show that this opposition is established by expression of Emx2 in half of the HCs, where it mediates hair bundle reversal (Jiang et al. 2017). Here, we show that Emx2 also regulates neuronal selection: afferent neurons innervate either Emx2-positive or negative HCs. In emx2 knockout and gain-of-function neuromasts, all HCs are unidirectional and the innervation patterns and physiological responses of the afferent neurons are dependent on the presence or absence of Emx2. Our results indicate that Emx2 mediates the directional selectivity of neuromasts by two distinct processes: regulating hair bundle orientation in HCs and selecting afferent neuronal targets.
All data generated or analysed during this study are included in the manuscript. Source data files have been provided for Table1 and figure 2, 4, 5, 6, 7, and 8.
- Katie Kindt
- Doris K Wu
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Marianne Bronner, California Institute of Technology, United States
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