The Luteinizing Hormone Releasing Hormone System

LHRH(也称为GnRH-1)神经元对生殖至关重要，它们来自鼻侧胎盘，并迁移到大脑中，在那里它们成为下丘脑-垂体-性腺轴的组成部分。我们在正常/转基因动物和鼻腔外植体中研究了促性腺激素释放激素神经元分化、迁移和轴突定位的机制(S)。利用这些相同的模型，我们的工作还研究了LHRH神经元(内在和跨突触)LHRH基因表达、多肽合成和分泌的调节机制。多种方法被用来识别和理解在引导LHRH神经元到达其在中枢神经系统中的最终位置方面起作用的众多分子和因素。这些包括从迁移和非迁移细胞中获得的文库的差异筛选，迁移路线上关键位置差异表达的分子的检查，LHRH系统在基因敲除小鼠中发育的形态检查，以及分子在体外的扰动和随后对LHRH神经元运动的监测。随着LHRH神经元的迁移，它们也会成熟，这两个过程实际上可能是联系在一起的。为了研究LHRH神经元的成熟，我们使用钙成像、电生理和生化方法来检测LHRH神经元的活性和多肽的分泌。 在过去几年的工作基础上，通过免疫细胞化学定位GAD67基因敲除小鼠的LHRH细胞的发育，进一步研究了GABA在LHRH神经元迁移中的作用。就像在迄今为止检查的许多动物模型中一样，LHRH系统尽管发生了改变，但能够补偿GABA的损失。此外，我们还在继续用分子和形态方法鉴定LHRH在发育中的切牙中的表达，并正在确定这些LHRH细胞和来自鼻侧胎盘的神经内分泌LHRH细胞之间的谱系关系，以及可能对启动LHRH基因表达起重要作用的共同转录因子。正在进行的研究集中在NELF(a？迁徙？LHRH发育中的分子)、细胞因子和生长因子以及LHRH神经元迁移的原位表征(实时显微镜)。此外，我们继续研究雌激素对LHRH神经元活性的作用，最近完成了LHRH神经元之间的差异筛选(从单个LHRH细胞构建)。雌二醇治疗。目前，已确定的基因正在细胞水平上进行检测(使用免疫细胞化学和/或原位杂交组织化学)。这些研究将确定最好的候选基因，以继续进行表征。正在进行的研究检查与LHRH神经元活动相关的电特性(结合电记录和钙成像)。未来的研究旨在扩展我们目前的结果，并针对对嗅觉和LHRH神经元系统的发育至关重要的分子和信号，以及调节LHRH神经元活动的机制。正在进行的具体研究集中在：1)分离影响嗅轴突生长的中线信号；2)NELF和其他分子在LHRH迁移中的作用；3)识别LHRH神经元中参与节律活动建立/维持的起搏分子；4)作为GABA能信号的功能在LHRH神经元中差异表达的基因；5)雌激素改变LHRH神经元活性的机制。

LHRH (also known as GnRH-1) neurons, critical for reproduction, are derived from the nasal placode and migrate into the brain where they become integral members of the hypothalamic-pituitary-gonadal axis. We study mechanism(s) underlying LHRH neuronal differentiation, migration and axonal targeting in normal/transgenic animals, and nasal explants. Using these same models, our work also addresses the mechanisms regulating (intrinsic and trans-synaptic) LHRH gene expression, peptide synthesis and secretion in LHRH neurons. Multiple approaches are used to identify and understand the multitude of molecules and factors which play a role in directing the LHRH neurons to their final location in the CNS. These include differential screening of libraries obtained from migrating versus non-migrating cells, examination of molecules differentially expressed at key locations along the migratory route, morphological examination of the development of the LHRH system in knockout mice, and perturbation of molecules in vitro and subsequent monitoring of LHRH neuronal movement. As LHRH neurons migrate they also mature and the two processes may in fact be linked. To investigate the maturation of LHRH neurons we use calcium imaging, electrophysiology and biochemical measures to examine LHRH neuronal activity and peptide secretion. Continuing on work from the past years, further investigations into the role of GABA in LHRH neuronal migration was examined by mapping the development of LHRH cells in GAD67 knockout mice using immunocytochemistry. As in many of the animal models examined to date, the LHRH system although altered, is able to compensate for the loss of GABA. In addition we are continuing to characterize, using molecular and morphological approaches, LHRH expression in the developing incisor and are determining the lineage relation between these LHRH cells and neuroendocrine LHRH cells derived from the nasal placode as well as common transcription factors that might be important for initiating LHRH gene expression. Studies in progress center on the role of NELF (a ?migrational? molecule), cytokines, and growth factors in LHRH development as well as in situ characterization of the migration of LHRH neurons (real time microscopy). In addition, we continue to study the role of estrogen on LHRH neuronal activity and have recently finished a differential screen (constructed from single LHRH cells) between LHRH neurons ? estrodiol treatment. Currently, the genes identified are being examined at the cellular level (using either immunocytochemistry and/or in situ hybridization histochemistry). These studies will identify the best candidate genes to continue to characterize. Studies in progress examine the electrical properties associated with LHRH neuronal activity (combining electrical recording and calcium imaging). Future studies are designed to expand upon our present results and are directed at the molecules and cues important for development of the olfactory and LHRH neuronal systems as well as the mechanisms regulating LHRH neuronal activity. Specific studies in progress focus on: 1) isolation of midline cues which influence olfactory axon outgrowth; 2) the role of NELF and other molecules in LHRH migration, 3) identifying pacemaker molecules in LHRH neurons that participate in establishment/maintenance of rhythmic activity, 4) genes differentially expressed in LHRH neurons as a function of GABAergic signals and 5) the mechanisms by which estrogen alters LHRH neuronal activity.