Sensory Axon Pathfinding

感觉轴突寻路

• 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
• 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
• 来源: https://reporter.nih.gov/project-details/7227797
• 关键词: Address; Affect; Afferent Neurons; Axon; BMP4; Biological Assay; Cells; Chick Embryo; Cues; Cutaneous; Dermal; Development; Dominant-Negative Mutation; Dorsal; Ectoderm; Electroporation; Embryo; Excision; Failure; Goals; Growth; Hindlimb; In Situ Hybridization; Individual; Knowledge; Label; Lateral; Limb Bud; Limb structure; Mediating; Mesenchyme; Mining; Molecular; Motor Neurons; Muscle; NTF3 gene; Natural regeneration; Nerve; Nerve Growth Factor 1; Nerve Growth Factor Pathway; Neural Crest; Neurons; Neurotrophin 3; Numbers; Operative Surgical Procedures; Pathway interactions; Peripheral Nerves; Peripheral nerve injury; Research; Research Personnel; Sensory; Signal Pathway; Signal Transduction; Skin; Surface; Time; axon growth; bone morphogenetic protein receptors; improved; insight; loss of function; novel strategies; programs; receptor; research study; response; theories; tissue culture

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）：我的研究的目的是了解轴突在开发过程中如何沿正确的途径生长。为了解决这个问题，我们研究了投射到小鸡后肢的感觉轴突。与不需要肌肉本身存在的运动神经元轴突形成肌肉神经相反，皮肤对于皮肤投射的正常发育至关重要。我们的手术操作表明，胚胎小鸡肢中主要皮肤神经的初始形成，股骨外侧皮肤（LFCT）神经需要在关键时期内存在靶性外胚层，而这些轴突即将与后肢的幽默有所不同。为了阐明潜在机制，我们表征了外胚层去除对肢体表达的各种分子的影响。重要的是，BMP4表达被下调，BMP4浸泡的珠子放在裸露的肢体表面救出的LFCT神经形成上。在拟议的研究中，我们将继续进行持续的努力，以利用雏鸡胚胎进行手术和分子操作的可及性，以阐明负责皮肤神经形成的机制。 1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充质发出信号的方式来确定其效应，从而依次会引起LFCT神经的形成。为了区分这些可能性并阐明BMP4作用的分子机制，提出的实验将表征BMP受体在DRG和肢体中的表达。使用各种功能丧失方法（通过电穿孔针对的肢体芽或神经rest（转染DRG神经元））的扰动BMP4信号传导；并使用互补的组织培养测定法检查BMP4挽救LFCT神经形成的细胞机制。其他研究将决定皮肤的线索如何促进LFCT神经的形成。这些将集中在NGF和NTS上，以表征它们在肢体中的表达，第一个皮肤轴突上相关受体的表达将投射到皮肤上，并检查外源性NGF和/或NT3是否挽救了去除术后的LFCT神经形成。拟议的研究将有助于我们了解皮肤的离散区域如何使皮肤神经投射到其上的形成，从而洞悉外周神经损伤后改善再生的方法。