DEVELOPMENT AND REGULATION OF THE LUTEINIZING HORMONE RELEASING HORMONE SYSTEM

LHRH神经元，生殖的关键，来自嗅觉 基板和迁移到大脑，在那里他们成为不可分割的成员 下丘脑-垂体-性腺轴我们研究机制（S） 正常/转基因动物中潜在的LHRH神经元迁移，以及 鼻外植体。 LHRH基因的内在和跨突触调节 胚胎LHRH神经元的表达、肽合成和分泌 （CNS外）与出生后LHRH神经元（CNS内）进行了研究 分别使用鼻外植体和器官型培养物。LHRH 神经元表达GABA受体，GABA能神经元存在于 鼻区 在体外，LHRH神经元的迁移被：a）抑制， a）GABA激动剂，B）GABA拮抗剂和用 河豚毒素我们假设GABA能信号调节 LHRH神经元进入中枢神经系统。 研究N的作用- 糖基化对LHRH发育的影响，我们发现衣霉素处理 显著改变的嗅觉轴突生长-纤维穿越 在嗅窝（OP）之间，而不是在 到达中线组织。 虽然嗅觉轴突的生长发生了变化， 治疗没有破坏LHRH神经元与其轴突的联系， 通路，也没有运动的LHRH神经元从OP，表明， 这些事件背后的分子机制独立于N- 糖基化中线/OP关系的操作证实， 用于嗅觉轴突的适当定位的导航信号 由软骨中线组织表达。探讨 基因表达、生物合成和分泌之间的关系， 检测多巴胺能（DA）神经元和LHRH的mRNA周转率 神经元酪氨酸羟化酶（TH; DA神经元的标志物）的差异 mRNA周转率之间发现下丘脑DA人群， 弓状神经元表现出TH mRNA周转率（6-7小时）， 与这些神经元显示的已知节律输出相对应。 LHRH神经分泌是脉动的（约1小时）。 保持这种 脉动的轮廓，我们假设LHRH mRNA迅速衰减。 我们 确定LHRH mRNA快速衰减（5-13分钟），随后 衰减速率慢得多（329-344分钟）。 值得注意的是， LHRH mRNA的表达速率对应于LHRH脉冲的快速衰减速率。 通过比较哺乳动物LHRH mRNA的3 'UTR，我们鉴定了两个 可能参与观察到的周转的保守区域 动力学目前，我们正在确定：1）中线线索， 影响嗅觉轴突的生长; 2） LHRH神经元与其轴突通路之间的相互作用; 3）基因 其选择性地在迁移的LHRH神经元中表达; 4） 表达甘丙肽的细胞与分化的关系和/或 LHRH神经元的迁移; 5）与快速LHRH mRNA相关的因素 周转

LHRH neurons, critical for reproduction, are derived from the olfactory placode and migrate into the brain, where they become integral members of the hypothalamic-pituitary-gonadal axis. We study mechanism(s) underlying LHRH neuronal migration in normal/transgenic animals, and nasal explants. Intrinsic and trans-synaptic regulation of LHRH gene expression, peptide synthesis and secretion in embryonic LHRH neurons (outside the CNS) versus postnatal LHRH neurons (in the CNS) is studied using nasal explants and organotypic cultures, respectively. LHRH neurons express GABA receptors and GABAergic neurons are present in nasal regions. In vitro, migration of LHRH neurons is: a) inhibited by a GABA agonist, b) increased by GABA antagonists and treatment with tetrodotoxin. We hypothesize that GABAergic signals regulate the timing of entrance of LHRH neurons into the CNS. Examining the role of N- glycosylation on LHRH development, we found that tunicamycin treatment dramatically altered olfactory axon outgrowth - with fibers traversing between olfactory pits (OP), instead of exiting the explant upon reaching midline tissue. Although outgrowth of olfactory axons changed, treatment did not disrupt association of LHRH neurons with their axonal pathway, nor movement of LHRH neurons from the OP, indicating that the molecular mechanism(s) underlying these events is independent of N- gycosylation. Manipulations of midline/OP relation confirmed that a navigational signal(s) for appropriate positioning of olfactory axons is expressed by cartilagenous midline tissue. To investigate the relationship between gene expression, biosynthesis and secretion, we examined mRNA turnover rates in dopaminergic (DA) neurons and LHRH neurons. Differences in tyrosine hydroxlase (TH; marker of DA neurons) mRNA turnover rates were found between hypothalamic DA populations, with arcuate neurons exhibiting a TH mRNA turnover rate (6-7 hr) which corresponded to the known rhythmic output displayed by these neurons. LHRH neurosecretion is pulsatile (about 1 hr ). To maintain this pulsatile profile, we hypothesized that LHRH mRNA rapidly decays. We determined that there is a fast decay of LHRH mRNA (5-13 min), followed by a much slower decay rate (329-344 min). Notably, the rapid decay rate of LHRH mRNA corresponds to the rapid decay rate of LHRH pulses. By comparing the 3'UTR of mammalian LHRH mRNAs, we identified two conserved regions which may be involved in the observed turnover kinetics. Currently, we are determining: 1) the midline cues which influence olfactory axon outgrowth; 2) the molecular nature of the interaction between LHRH neurons and their axonal pathway; 3) genes which are selectively expressed in migrating LHRH neurons; 4) the relation of galanin expressing cells to the differentiation and/or migration of LHRH neurons and; 5) factors related to rapid LHRH mRNA turnover.