The asymmetric hair bundle on top of hair cells (HCs), comprises a kinocilium and stereocilia staircase, dictates HC directional sensitivity. The mother centriole (MC) forms the base of the kinocilium, where stereocilia are subsequently built next 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 towards 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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小鼠尿囊中毛束极性采集的实时成像显示了转录因子Emx2的关键时间表

毛细胞（HC）顶部的不对称发束包括运动蛋白和立体纤毛阶梯，决定了HC方向的敏感性。中心母细胞（MC）形成了动毛虫的基础，随后在其附近建立了纤毛虫。先前我们发现转录因子Emx2逆转了发束方向，并且其在小鼠前庭囊中的表达受到限制，从而导致两个相反的发束区域（Jiang等，2017）。在这里，我们调查了活的GFP标记的HCs的中心成像在胚胎尿囊中建立相反的束方向。子中心在MC之前总是从MC移到它们各自的外围位置。比较市区之间的HC 中心线轨迹相似，但是它们向相反的方向迁移，这表明Emx2在中心线迁移之前预先设定了模式。然而，当中心粒轨迹对Emx2做出响应时，在关键的时间窗口内，异位Emx2在数小时内反转了中心粒轨迹。