Regulation of Neuron Development by a Nuclear Receptor

在神经系统发育期间，神经元是由胚胎前体细胞产生的。随后，神经元彼此分离，形成无数种神经细胞类型，每种类型都有不同的身份。例如，参与嗅觉的神经元与那些调节呼吸的神经元有很大的不同。因此，神经元在生理、神经递质表达、轴突形态和突触连接方面变得不同。单个神经元身份被指定的机制还不是很清楚，但已知的是涉及到“开启”和“关闭”其他基因的蛋白质的活动。本研究的目的是通过研究线虫秀丽线虫的FAX-1基因，增加对神经元特性指定过程的理解。FAX-1编码一种核激素受体蛋白，这种蛋白可以开启和关闭其他基因。当FAX-1基因突变时，一些神经元不能正常形成。线虫是研究神经系统发育机制的一个很好的模式系统，它具有302个细胞的神经系统和几乎完全测序的基因组。其他在无脊椎动物神经系统发育中发挥作用的分子已经被证明在脊椎动物中具有类似的功能。一种与FAX-1相关的人类核激素受体已被鉴定，并被证明在人类光感受器细胞中特异表达。因此，对线虫中FAX-1的研究可能会为人类神经系统特异基因的功能提供信息。这项研究将通过识别一些受FAX-1调控的基因来研究神经元特性指定的分子机制。首先，将定义FAX-1蛋白与之结合的DNA序列。其次，将通过两种主要的实验方法来识别受FAX-1调控的基因。在一种方法中，在基于酵母的系统中识别FAX-1蛋白结合的特定DNA片段。在第二种方法中，使用最先进的DNA微阵列技术识别响应FAX-1而打开或关闭的基因。这项研究将促进我们对如何指定不同神经细胞类型这一基本生物学问题的了解，并可能定义一种从线虫到人类都保守的新的发育机制。另一个主要目标是通过让学生在一个分子遗传学研究项目中扮演主要角色来推进本科教育，该项目涉及“经典的”重组DNA和当前的基因组技术。

During nervous system development, neurons are generated from embryonic precursor cells. Subsequently, neurons diverge from each other to create myriad neuronal cell types, each with distinct identities. For example, neurons involved in smell are quite different from those that function in regulation of breathing. Thus neurons come to differ from each other in terms of physiology, neurotransmitter expression, axonal morphology, and synaptic connectivity. The mechanisms by which individual neuron identities are specified are not well understood, but are known to involve the activity of proteins that "turn on" and "off" other genes. The objective of this research is to increase understanding of the process of specification of neuron identity by studying the fax-1 gene of the nematode Caenorhabditis elegans. fax-1 encodes a nuclear hormone receptor protein, the type of protein that turns on and off other genes. When the fax-1 gene is mutated, some neurons don't form properly. The nematode is an excellent model system in which to study the mechanisms of nervous system development by virtue of its well-characterized 302-cell nervous system and its virtually completely-sequenced genome. Other molecules that function in invertebrate nervous system development have been shown to perform similar functions in vertebrates. A human nuclear hormone receptor related to fax-1 has been identified and shown to be expressed specifically in human photoreceptor cells. Therefore, a study of fax-1 in C. elegans may inform on the function of a human nervous system-specific gene. This study will investigate the molecular mechanism of specification of neuron identity by identifying some of the genes that are regulated by fax-1. First, the DNA sequence to which the FAX-1 protein binds will be defined. Second, the genes that are regulated by fax-1 will be identified through two major experimental approaches. In one approach specific DNA fragments to which the FAX-1 protein binds are identified in a yeast-based system. In a second approach, genes that are turned on or off in response to fax-1 are identified using state-of-the-art DNA microarray technology. This research will advance our knowledge about the basic biological question of how different neuronal cell types are specified and may define a new developmental mechanism that is conserved from nematodes to humans. An additional major goal is to advance undergraduate education by giving students primary roles in a molecular genetic research project that involves both "classical" recombinant DNA and current genomic technologies.