Corwin J T, Cotanche D A
Department of Otolaryngology, University of Virginia School of Medicine, Charlottesville 22908.
J Comp Neurol. 1989 Oct 22;288(4):529-37. doi: 10.1002/cne.902880402.
The developmental mechanisms that allow physiological coding of acoustic pitch have remained unexplained. Cochlear hair cells that have different structures respond to different sound frequencies and synapse with neurons that project to different locations in the brain. How do these hair cells develop appropriate structures, and how are the connections between specific hair cells and the neurons that code for their pitch sensitivities matched? We have investigated one aspect of this by denervating embryonic chicken ears, before the time of hair cell production, and then transplanting them to the aneural chorioallantoic membrane of host embryos where they have continued to develop. We report that vestibular and auditory hair cell phenotypes differentiate appropriately and that correct gradients of hair cell structural phenotypes, as expressed in stereocilia bundles, develop in the cochleae of these denervated ears. Therefore, the normal development of gradients in hair cell stereocilia properties must be controlled by location-specific cues originating in the ear itself. Neuronally directed modification of target cell phenotypes is not required for the quite specific phenotype development represented by the stereocilia bundles of individual hair cells and the connectional matching in the numerous distinct peripheral information lines of the auditory system.
能够对音频音调进行生理编码的发育机制一直未得到解释。具有不同结构的耳蜗毛细胞对不同的声音频率做出反应，并与投射到大脑不同位置的神经元形成突触。这些毛细胞是如何发育出合适的结构的，以及特定毛细胞与编码其音调敏感性的神经元之间的连接是如何匹配的？我们通过在毛细胞产生之前去除胚胎期鸡耳的神经支配，然后将其移植到宿主胚胎的无神经绒毛尿囊膜上，在那里它们继续发育，研究了这个问题的一个方面。我们报告称，前庭和听觉毛细胞表型能够正常分化，并且在这些去神经支配耳朵的耳蜗中，如在静纤毛束中所表现的那样，毛细胞结构表型的正确梯度得以形成。因此，毛细胞静纤毛特性梯度的正常发育必定受源自耳朵自身的位置特异性线索控制。对于由单个毛细胞的静纤毛束所代表的相当特异的表型发育以及听觉系统众多不同外周信息线路中的连接匹配而言，并不需要神经元对靶细胞表型进行定向修饰。
