Section on Sensory Cell Regeneration and Development, Laboratory of Molecular Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, 20892, USA.
Sensory & Motor Systems Research Group, Korea Brain Research Institute (KBRI), 61 Cheomdan-ro, Dong-gu, Daegu, 41062, Republic of Korea.
Nat Commun. 2022 Oct 24;13(1):6330. doi: 10.1038/s41467-022-33819-3.
Otolith organs of the inner ear are innervated by two parallel afferent projections to the brainstem and cerebellum. These innervations were proposed to segregate across the line of polarity reversal (LPR) within each otolith organ, which divides the organ into two regions of hair cells (HC) with opposite stereociliary orientation. The relationship and functional significance of these anatomical features are not known. Here, we show regional expression of Emx2 in otolith organs, which establishes LPR, mediates the neuronal segregation across LPR and constitutes the bidirectional sensitivity function. Conditional knockout (cKO) of Emx2 in HCs lacks LPR. Tmie cKO, in which mechanotransduction was abolished selectively in HCs within the Emx2 expression domain also lacks bidirectional sensitivity. Analyses of both mutants indicate that LPR is specifically required for mice to swim comfortably and to traverse a balance beam efficiently, but LPR is not required for mice to stay on a rotating rod.
内耳的耳石器官由两条平行的传入投射到脑干和小脑支配。这些支配被认为是在每个耳石器官内的极性反转线（LPR）上分隔的，该线将器官分为具有相反的纤毛取向的两个毛细胞（HC）区域。这些解剖学特征的关系和功能意义尚不清楚。在这里，我们显示了 Emx2 在耳石器官中的区域表达，它建立了 LPR，介导了 LPR 上的神经元分隔，并构成了双向敏感性功能。Emx2 在 HC 中的条件敲除（cKO）缺乏 LPR。在 Emx2 表达域内的 HC 中选择性地消除机械转导的 Tmie cKO 也缺乏双向敏感性。对这两种突变体的分析表明，LPR 是小鼠舒适游泳和高效穿越平衡木所必需的，但 LPR 不是小鼠在旋转杆上保持稳定的必需条件。
