Regulation of the Gene for the L1 Cell Adhesion Molecule by Homeodomain and Pax Proteins in Response to Bone Morphogenetic Proteins (BMPs)

伊本- 9816896;细胞粘附分子（CAMs）在神经系统发育过程中对细胞的组织及其相互连接起着重要作用。CAMs表达的改变伴随着一些发育异常。了解调节这些分子基因的因素将进一步确定它们在神经发育中的作用。一个丰富的调节控制网络负责CAM表达的神经模式。在这个提议中，琼斯博士将检查一种叫做L1的特定CAM的表达。L1基因的突变会产生异常的大脑发育，与x连锁痉挛性截瘫、x连锁脑积水和智力低下以及胼胝体发育不全等综合征相关。在初步实验中，我们对L1基因的调控区域及其启动子进行了鉴定和表征。确定了对其在神经系统中的表达至关重要的两个DNA调控元件。其中包括一个神经元限制性沉默元件（NRSE），它可以阻止L1在非神经组织中的表达，以及一个同源盒和Pax家族转录因子的结合位点（HPD），这是中枢神经系统L1表达所必需的。HPD也是一个重要的生长因子家族——骨形态发生蛋白（BMPs）——诱导L1表达所必需的。在本研究中，将确定在神经发育过程中与HPD结合并控制L1表达的蛋白因子的性质。我们将确定神经细胞和非神经细胞中BMP2和BMP4调控L1表达的具体因子，并确定NRSE及其结合因子REST/NRSF是否会阻碍非神经细胞中L1表达的BMP激活。最后，HPD在神经发育过程中的作用将以多种方式进行研究。我们将比较含有和缺乏HPD的L1基因在不同转基因小鼠中的表达模式。BMP2、BMP4及其受体（BMPR-I和BMPR-II）将与特定的同源盒和Pax转录因子一起定位，这些转录因子结合并通过HPD调节L1表达。这样的实验将有助于深入了解BMP信号传导和同源盒和Pax蛋白的转录控制在体内调节L1表达的细胞背景。总的来说，这些实验的结果应该提供了一个重要的细胞外信号分子家族，已知控制神经分化区域模式的转录调节因子和神经细胞粘附过程之间的联系。

IBN-9816896; JONES, Frederick Cell adhesion molecules (CAMs) play an important role in organizing cells and their interconnections during development of the nervous system. Alterations in the expression of CAMs accompany a number of developmentals abnormalities. Understanding factors that regulate the genes for these molecules would further define their role in neural development. A rich network of regulatory controls is responsible for neural patterns of CAM expression. In this proposal, Dr. Jones will examine the expression of a particular CAM called L1. Mutations in the L1 gene produce aberrant brain development linked to syndromes that include X-linked spastic paraplegia, X-linked hydrocephalus and mental retardation, and agenesis of the corpus collosum. In preliminary experiments, the regulatory region of the L1 gene including its promoter was identified and characterized. The two DNA regulatory elements that were critical for its expression in the nervous system were determined. These include a neuron-restrictive silencer element (NRSE) which prevents L1 expression in non-neural tissues and a binding site (HPD) for transcription factors of the homeobox and Pax families which is necessary for expression of L1 in the central nervous system. The HPD is also necessary for induction of L1 expression by an important family of growth factors, the bone morphogenetic proteins (BMPs). In this proposal, the nature of the protein factors that bind to the HPD and control L1 expression during neural development will be determined. Specific factors that are responsible for regulation of L1 expression by BMP2 and BMP4 in neural and non-neural cells will be identified and it will be determine whether the NRSE and its binding factor REST/NRSF impede BMP activation of L1 expression in non-neural cells. Finally, the role of the HPD during neural development will be examined in a number of ways. The expression patterns of L1 transgenes containing and lacking the HPD will be compared in different transgenic mice. BMP2, BMP4, their receptors (BMPR-I and BMPR-II) will be localized along with the particular homeobox and Pax transcription factors that bind to and regulate L1 expression via the HPD. Such experiments will help provide insight into the cellular contexts in which BMP signaling and transcriptional control by homeobox and Pax proteins regulate L1 expression in vivo. Overall, the results from these experiments should provide a connection between an important family of extracellular signalling molecules, transcriptional regulators that are known to control regional patterns of neural differentiation, and the process of neural cell adhesion.