The mouse auditory organ cochlea contains two types of sound receptors: inner hair cells (IHCs) and outer hair cells (OHCs). Tbx2 is expressed in IHCs but repressed in OHCs, and neonatal OHCs that misexpress Tbx2 transdifferentiate into IHC-like cells. However, the extent of this switch from OHCs to IHC-like cells and the underlying molecular mechanism remain poorly understood. Furthermore, whether Tbx2 can transform fully mature adult OHCs into IHC-like cells is unknown. Here, our single-cell transcriptomic analysis revealed that in neonatal OHCs misexpressing Tbx2, 85.6% of IHC genes, including Slc17a8, are upregulated, but only 38.6% of OHC genes, including Ikzf2 and Slc26a5, are downregulated. This suggests that Tbx2 cannot fully reprogram neonatal OHCs into IHCs. Moreover, Tbx2 also failed to completely reprogram cochlear progenitors into IHCs. Lastly, restoring Ikzf2 expression alleviated the abnormalities detected in Tbx2+ OHCs, which supports the notion that Ikzf2 repression by Tbx2 contributes to the transdifferentiation of OHCs into IHC-like cells. Our study evaluates the effects of ectopic Tbx2 expression on OHC lineage development at distinct stages of either male or female mice and provides molecular insights into how Tbx2 disrupts the gene expression profile of OHCs. This research also lays the groundwork for future studies on OHC regeneration.

小鼠听觉器官耳蜗含有两种类型的声音感受器：内毛细胞（IHC）和外毛细胞（OHC）。 Tbx2 在 IHC 中表达，但在 OHC 中受到抑制，错误表达 Tbx2 的新生儿 OHC 转分化为 IHC 样细胞。然而，从 OHC 到 IHC 样细胞的转变程度以及潜在的分子机制仍然知之甚少。此外，Tbx2是否可以将完全成熟的成人OHC转化为IHC样细胞尚不清楚。在这里，我们的单细胞转录组分析显示，在错误表达 Tbx2 的新生儿 OHC 中，85.6% 的 IHC 基因（包括Slc17a8 ）上调，但只有 38.6% 的 OHC 基因（包括Ikzf2和Slc26a5 ）下调。这表明 Tbx2 不能将新生儿 OHC 完全重编程为 IHC。此外，Tbx2 也未能将耳蜗祖细胞完全重编程为 IHC。最后，恢复 Ikzf2 表达减轻了 Tbx2+ OHC 中检测到的异常，这支持了 Tbx2 抑制 Ikzf2 有助于 OHC 向 IHC 样细胞转分化的观点。我们的研究评估了异位 Tbx2 表达对雄性或雌性小鼠不同阶段的 OHC 谱系发育的影响，并提供了 Tbx2 如何破坏 OHC 基因表达谱的分子见解。这项研究也为未来 OHC 再生的研究奠定了基础。