Davies A M, Wyatt S, Nishimura M, Phillips H
School of Biological and Medical Sciences, University of St. Andrews, Scotland.
Dev Biol. 1995 Oct;171(2):434-8. doi: 10.1006/dbio.1995.1293.
Numerous in vivo and in vitro studies have shown that NGF increases the expression of its receptors, p75 and TrkA, in NGF-responsive cell lines and in NGF-responsive neurons of the developing and mature nervous system. To determine if endogenous NGF is required for the normal developmental increase in p75 and TrkA expression that occurs in sensory neurons shortly after they innervate their targets, we used quantitative RT/PCR to compare the levels of p75 and trkA mRNAs in the trigeminal ganglia of normal mouse embryos and embryos that are homozygous for a null mutation in the NGF gene. We show that the marked increase in p75 and trkA mRNA expression that occurs between E11 and E13 in normal embryos takes place on time and to the same extent in NGF-/- embryos. We also show that trigeminal neurons from E13 NGF+/+ and NGF-/- embryos have very similar dose responses for survival induced by NGF. These findings clearly show that the expression of both p75 and TrkA and the sensitivity of developing sensory neurons to NGF do not require and are not modulated by target-derived NGF during the early stages of target field innervation.
大量的体内和体外研究表明，在发育中和成熟的神经系统中，神经生长因子（NGF）可增加其受体p75和酪氨酸激酶受体A（TrkA）在NGF反应性细胞系以及NGF反应性神经元中的表达。为了确定在感觉神经元支配其靶标后不久，其p75和TrkA表达正常发育性增加是否需要内源性NGF，我们使用定量逆转录聚合酶链反应（RT/PCR）比较了正常小鼠胚胎和NGF基因纯合无效突变胚胎三叉神经节中p75和trkA信使核糖核酸（mRNA）的水平。我们发现，正常胚胎在胚胎第11天（E11）至第13天（E13）之间p75和trkA mRNA表达的显著增加在NGF基因敲除（NGF-/-）胚胎中按时且以相同程度发生。我们还表明，来自E13野生型（NGF+/+）和NGF-/-胚胎的三叉神经节神经元对NGF诱导的存活具有非常相似的剂量反应。这些发现清楚地表明，在靶标区域支配的早期阶段，p75和TrkA的表达以及发育中的感觉神经元对NGF的敏感性并不需要靶标来源的NGF，也不受其调节。
