In the mature cochlea, each inner hair cell (IHC) is innervated by multiple spiral ganglion neurons of type I (SGNI). SGNIs are morphologically and electro-physiologically diverse. Also, they differ in their susceptibility to noise insult. However, the molecular underpinnings of their identity and physiological differences remain poorly understood. In this study, we developed a novel triple transgenic mouse, which enabled the isolation of pure populations of SGNIs and the analysis of a 96-gene panel via single-cell qPCR. We found three distinct populations of Type I SGNs, which were marked by their exclusive expression of Lmx1a, Slc4a4, or Mfap4/Fzd2, respectively, at postnatal days P3, P8, and P12. Our data suggest that afferent SGN subtypes are established genetically before the onset of hearing and that the expression of key physiological markers, such as ion channels, is heterogeneous and may be underlying the heterogeneous firing proprieties of SGNIs.

在成熟的耳蜗中，每个内部毛细胞（IHC）被I型多个螺旋神经节神经元（SGNI）支配。SGNIs在形态和电生理上是多样的。而且，它们对噪声侮辱的敏感性也不同。然而，对其身份和生理差异的分子基础仍然知之甚少。在这项研究中，我们开发了一种新型三重转基因小鼠，该小鼠能够分离出SGNIs的纯种群并分析了96个基因通过单细胞qPCR。我们发现了三个不同的I型SGN种群，它们的独特表达是Lmx1a，Slc4a4， 要么 Mfap4 / Fzd2分别在出生后第3天，第8天和第12天。我们的数据表明，传入SGN亚型是在听力发作之前通过基因建立的，并且关键生理标记（例如离子通道）的表达是异质的，并且可能是SGNIs异质激发的基础。