Harper S, Davies A M
Department of Anatomy, St George's Hospital Medical School, Tooting, London, UK.
Development. 1990 Oct;110(2):515-9. doi: 10.1242/dev.110.2.515.
To determine if the initial level of NGF mRNA in developing cutaneous epithelium is correlated with its final innervation density, we measured the concentration of NGF mRNA in the epithelia of the maxillary, mandibular and ophthalmic territories of trigeminal ganglion in the embryonic mouse. At the onset of neuronal death in the ganglion there were marked differences in the concentration of NGF mRNA in these epithelia: the level was highest in the epithelium of the densely innervated maxillary territory, it was lower in the epithelium of the moderately innervated mandibular territory and was lowest in the epithelium of the sparsely innervated ophthalmic territory. These regional differences in the level of NGF mRNA during the early stages of target field innervation suggest that the level of NGF production in target field cells, rather than regional differences in the access of innervating neurons to NGF, governs the number of neurons that survive. Because the same percentage cell death occurs in each of the subsets of trigeminal neurons that innervate the maxillary, mandibular and ophthalmic territories, regional differences in NGF synthesis are not responsible for establishing differences in innervation density, rather they maintain differences that arise earlier in development.
为了确定发育中的皮肤上皮中神经生长因子（NGF）mRNA的初始水平是否与其最终的神经支配密度相关，我们测量了胚胎小鼠三叉神经节上颌、下颌和眼神经区域上皮中NGF mRNA的浓度。在神经节神经元死亡开始时，这些上皮中NGF mRNA的浓度存在显著差异：在神经支配密集的上颌区域上皮中水平最高，在神经支配中等的下颌区域上皮中较低，而在神经支配稀疏的眼神经区域上皮中最低。在靶场神经支配早期阶段，NGF mRNA水平的这些区域差异表明，靶场细胞中NGF的产生水平，而非支配神经元获取NGF的区域差异，决定了存活神经元的数量。因为支配上颌、下颌和眼神经区域的三叉神经元亚群中，每个亚群发生的细胞死亡百分比相同，所以NGF合成的区域差异并非负责建立神经支配密度的差异，而是维持发育早期出现的差异。
