Directional sensitivity of hair cells (HCs) is conferred by the aymmetric apical hair bundle, comprised of a kinocilium and stereocilia staircase. The mother centriole (MC) forms the base of the kinocilium and the stereocilia develop adjacent to it. Previously, we showed that transcription factor Emx2 reverses hair bundle orientation and its expression in the mouse vestibular utricle is restricted, resulting in two regions of opposite bundle orientation (Jiang et al., 2017). Here, we investigated establishment of opposite bundle orientation in embryonic utricles by live-imaging GFP-labeled centrioles in HCs. The daughter centriole invariably migrated ahead of the MC from the center to their respective peripheral locations in HCs. Comparing HCs between utricular regions, centriole trajectories were similar but they migrated toward opposite directions, suggesting that Emx2 pre-patterned HCs prior to centriole migration. Ectopic Emx2, however, reversed centriole trajectory within hours during a critical time-window when centriole trajectory was responsive to Emx2.

中文翻译：

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发束极性采集的实时成像展示了转录因子 Emx2 的关键时间线


毛细胞 (HC) 的方向敏感性是由不对称的顶端毛束赋予的，该毛束由动纤毛和静纤毛阶梯组成。母中心粒 (MC) 形成动纤毛的基础，静纤毛在其附近发育。此前，我们发现转录因子Emx2可以逆转发束方向，并且其在小鼠前庭椭圆囊中的表达受到限制，导致两个区域的发束方向相反(Jiang et al., 2017)。在这里，我们通过对 HC 中 GFP 标记的中心粒进行实时成像，研究了胚胎椭圆囊中相反束方向的建立。子中心粒总是先于 MC 从中心迁移到 HC 中各自的外围位置。比较椭圆囊区域之间的 HC，中心粒轨迹相似，但它们向相反方向迁移，表明 Emx2 在中心粒迁移之前预先图案化 HC。然而，当中心粒轨迹对 Emx2 做出响应时，异位 Emx2 在关键时间窗口内的数小时内逆转了中心粒轨迹。