Bernd P, Zhang D, Yao L, Rozenberg I
Department of Anatomy and Cell Biology, State University of New York, Health Science Center at Brooklyn 11203, USA.
Int J Dev Neurosci. 1994 Dec;12(8):709-23. doi: 10.1016/0736-5748(94)90051-5.
The role of the nerve growth factor family of neurotrophins in the development of cochlear and vestibular ganglia is unclear. In order to predict the potential importance of nerve growth factor, brain-derived neurotrophic factor or neurotrophin-3, we examined the expression of neurotrophin mRNA and full-length neurotrophin receptor mRNA by in-situ hybridization and reverse transcription-polymerase chain reaction, as well as whether high affinity 125I-nerve growth factor binding was present, in cochlear and vestibular ganglia of the quail at several stages of development (stages 26, 31 and 36). Nerve growth factor, brain-derived neurotrophic factor and neurotrophin-3 mRNA was detected at all ages examined, suggesting that these neurotrophins may serve an autocrine or paracrine function, especially prior to target contact. In addition, we found full-length trkA and trkC mRNA was expressed, the products of which are the functional neuronal receptors for nerve growth factor and neurotrophin-3, respectively. Although full-length trkA mRNA was found, physiologically important high affinity 125I-nerve growth factor binding was not detected. Since nerve growth factor's effects on survival and neurite outgrowth are mediated through high affinity binding, nerve growth factor may serve an as yet unidentified role in this system. Full-length trkB mRNA, the product of which is the functional neuronal receptor for brain-derived neurotrophic factor, was not detected using reverse transcription-polymerase chain reaction, however, truncated (non-catalytic) trkB was present, at least in cochlear ganglia at stage 31. It is not known what function may be subserved by these truncated receptors.
神经营养因子家族中的神经生长因子在耳蜗神经节和前庭神经节发育过程中的作用尚不清楚。为了预测神经生长因子、脑源性神经营养因子或神经营养素-3的潜在重要性，我们通过原位杂交和逆转录聚合酶链反应检测了鹌鹑在几个发育阶段（第26、31和36阶段）耳蜗神经节和前庭神经节中神经营养因子mRNA和全长神经营养因子受体mRNA的表达，以及是否存在高亲和力的125I-神经生长因子结合。在所有检测的年龄段均检测到神经生长因子、脑源性神经营养因子和神经营养素-3 mRNA，这表明这些神经营养因子可能发挥自分泌或旁分泌功能，尤其是在与靶细胞接触之前。此外，我们发现全长trkA和trkC mRNA表达，其产物分别是神经生长因子和神经营养素-3的功能性神经元受体。虽然发现了全长trkA mRNA，但未检测到具有生理重要性的高亲和力125I-神经生长因子结合。由于神经生长因子对存活和神经突生长的作用是通过高亲和力结合介导的，神经生长因子在该系统中可能发挥尚未明确的作用。使用逆转录聚合酶链反应未检测到全长trkB mRNA，其产物是脑源性神经营养因子的功能性神经元受体，然而，至少在第31阶段的耳蜗神经节中存在截短的（无催化活性的）trkB。尚不清楚这些截短的受体可能具有什么功能。
