Development of the Primary Olfactory Pathway

描述（由申请人提供）：本项目的长期目标是确定参与建立初级嗅觉通路复杂拓扑结构的轴突导向分子。我们先前确定了轴突行为表明指导分子正在起作用的发育关键时间点。嗅感觉神经元（OSN）轴突在胚胎发育早期从嗅板生长到端脑泡。轴突穿过端脑，形成假定的嗅觉神经层（pONL）。一小部分轴突生长到脑室表面，这被认为是诱导嗅球（OB）形成的原因。大多数轴突仍然局限于pONL长达4天，推测分类成分子定义的子集。4天后，一些轴突生长到OB更深处，开始肾小球形成。理解嗅觉通路形成的一个关键问题是，在肾小球形成之前，OB中存在哪些线索阻止轴突向内生长？回答这个关键问题的一种方法是检查候选指导分子在发展途径中的分布。我们推测pONL内轴突的停滞可能是由于发育中的OB内的抑制性引导分子。OB中抑制性线索的一个潜在来源是细胞外基质（ECM）的组分。我们已经确定了腱生蛋白和硫酸软骨素蛋白聚糖（CSPGs）作为调节轴突向内生长和肾小球形成的抑制性线索的良好候选者。本发明的具体目的是：1）检验ECM的组分是发育中嗅觉通路中OSN轴突时空动力学的关键调节剂的假设，并在功能上检验这些分子在体外抑制OSN神经突生长的能力; 2）检验整联蛋白和非整联蛋白ECM受体都促进细胞表面-基质相互作用在发育中的嗅觉系统，并在功能上测试它们的能力，调节OSN神经突生长的ECM基板在体外; 3）测试的假设，基质金属蛋白酶发挥了重要作用，在造型的ECM环境在发展中的嗅觉系统。这些研究将大大提高我们对轴突如何在嗅觉系统中建立连接的认识，并可能对卡尔曼综合征等疾病产生影响。此外，这些结果将广泛适用于其他CNS区域，这些区域继续努力了解边界和地形图的形成。

DESCRIPTION (provided by applicant): The long term aim of this project is to identify axon guidance molecules involved in establishing the complex topography of the primary olfactory pathway. We previously identified critical time points in development where axon behavior indicates that guidance molecules are acting. Olfactory sensory neuron (OSN) axons grow from the olfactory placode to the telencephalic vesicle in early embryonic development. Axons penetrate the telencephalon, forming a presumptive olfactory nerve layer (pONL). A small subset of axons grow to the ventricular surface which has been suggested to induce the formation of olfactory bulb (OB). The majority of axons remain restricted to the pONL for up to 4 days, presumably sorting out into molecularly defined subsets. After 4 days, some axons grow deeper into the OB, initiating glomerular formation. A pivotal question in understanding olfactory pathway formation is which cue(s) are present in the OB that prevent(s) axon ingrowth prior to glomerular formation? One way to answer this key question is to examine the distributions of candidate guidance molecules within the developing pathway. We hypothesize that the stalling of axons within the pONL may be due to inhibitory guidance molecules within the developing OB. One potential source of inhibitory cues in the OB are components of the extracellular matrix (ECM). We have identified members of the tenascin and chondroitin sulfate proteoglycans (CSPGs) as good candidates for the inhibitory cues that regulate axon ingrowth and glomerular formation. The specific aims of the current proposal are to: 1) test the hypothesis that components of the ECM are key regulators of OSN axon spatio-temporal dynamics in the developing olfactory pathway, and to functionally test the ability of these molecules to inhibit OSN neurite outgrowth in vitro; 2) to test the hypothesis that both integrin and non-integrin ECM receptors facilitate cell surface - matrix interactions in the developing olfactory system and to functionally test their ability to modulate OSN neurite outgrowth on ECM substrates in vitro; 3) to test the hypothesis that the matrix metallooroteases play an important role in sculpting the ECM environment during development of the olfactory system. These studies will greatly enhance our knowledge of how axons establish connections in the olfactory system and may have implications for diseases such as Kallman's syndrome. Moreover these results will be broadly applicable to other CNS regions where work continues towards understanding the formation of boundaries and topographic maps.