Sensory Axon Pathfinding

感觉轴突寻路

基本信息

批准号：
7227797
负责人：
Marcia G Honig
金额：
$ 25.52万
依托单位：
UNIVERSITY OF TENNESSEE HEALTH SCI CTR
依托单位国家：
美国
项目类别：
财政年份：
1995
资助国家：
美国
起止时间：
1995-08-15 至 2010-06-30
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): The goal of my research is to understand how axons grow along the correct pathways during development. To address this issue, we study sensory axons projecting into the chick hindlimb. In contrast to motoneuron axons, which do not require the presence of muscle per se to form muscle nerves, the skin is essential for the normal development of cutaneous projections. Our surgical manipulations have shown that the initial formation of a major cutaneous nerve in the embryonic chick limb, the lateral femoral cutaneous (LFCt) nerve requires the presence of the target ectoderm during a critical time period, when those axons are about to diverge from the hindlimb plexus. To elucidate the underlying mechanisms, we characterized the effects of ectoderm removal on a variety of molecules expressed in the limb. Importantly, Bmp4 expression was downregulated and BMP4-soaked beads placed on the denuded limb surface rescued LFCt nerve formation. In the proposed studies, we will continue our ongoing efforts to elucidate the mechanisms responsible for cutaneous nerve formation, taking advantage of the accessibility of chick embryos for carrying out surgical and molecular manipulations. 1 major goal will be to determine whether BMP4 exerts its effects by directly affecting the outgrowth of cutaneous axons or by signaling the limb mesenchyme in a way that it in turn elicits LFCt nerve formation. To distinguish between these possibilities and elucidate the molecular mechanisms underlying BMP4 action, the proposed experiments will characterize the expression of BMP receptors in the DRGs and in the limb; perturb BMP4 signaling, using various loss-of-function approaches, targeted by means of electroporation, to either the limb bud or to the neural crest (to transfect DRG neurons); and use complementary tissue culture assays to examine the cellular mechanisms by which BMP4 rescues LFCt nerve formation. Other studies will determine how cues from the skin contribute to LFCt nerve formation. These will focus on NGF and NTS, characterizing their expression in the limb, the expression of the relevant receptors on the first cutaneous axons to project to the skin, and examining whether exogenous NGF and/or NT3 rescues LFCt nerve formation after ectoderm removal. The proposed studies will help us understand how discrete regions of the skin bring about the formation of the cutaneous nerve projecting to it, and thereby also provide insight into ways to improve regeneration following peripheral nerve injury.

描述（由申请人提供）：我的研究目标是了解轴突在发育过程中如何沿着正确的路径生长。为了解决这个问题，我们研究了投射到雏鸡后肢的感觉轴突。运动神经元轴突不需要肌肉本身来形成肌肉神经，与之相反，皮肤对于皮肤突起的正常发育至关重要。我们的手术操作表明，在胚胎鸡肢体中，股外侧皮神经（LFCt）的主要皮神经的最初形成需要在关键时间段内目标外胚层的存在，此时这些轴突即将从外胚层分叉。后肢神经丛。为了阐明潜在的机制，我们表征了外胚层去除对肢体中表达的各种分子的影响。重要的是，Bmp4 表达下调，将 BMP4 浸泡的珠子放置在裸露的肢体表面可以挽救 LFCt 神经的形成。在拟议的研究中，我们将继续努力阐明皮神经形成的机制，利用鸡胚胎的可及性进行手术和分子操作。第一个主要目标是确定 BMP4 是否通过直接影响皮肤轴突的生长或通过向肢体间质发出信号从而引发 LFCt 神经形成来发挥其作用。为了区分这些可能性并阐明 BMP4 作用的分子机制，拟议的实验将表征 BMP 受体在 DRG 和肢体中的表达；使用各种功能丧失方法扰乱 BMP4 信号传导，通过电穿孔靶向肢芽或神经嵴（转染 DRG 神经元）；并使用补充组织培养测定来检查 BMP4 拯救 LFCt 神经形成的细胞机制。其他研究将确定来自皮肤的信号如何促进 LFCt 神经的形成。这些研究将重点关注 NGF 和 NTS，表征它们在肢体中的表达，相关受体在第一个投射到皮肤的皮肤轴突上的表达，并检查外源性 NGF 和/或 NT3 是否可以在去除外胚层后挽救 LFCt 神经形成。拟议的研究将帮助我们了解皮肤的离散区域如何形成投射到其上的皮神经，从而也为改善周围神经损伤后的再生提供了见解。