DEVELOPMENT AND REGULATION OF THE LUTEINIZING HORMONE RELEASING HORMONE SYSTEM

对生殖至关重要的LHRH神经元是 来源于嗅觉定位，并迁移到大脑中， 在那里，他们成为 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， 还有鼻腔外植体。促性腺激素释放激素的内源性和跨突触调节 胚胎中的基因表达、多肽合成和分泌 LHRH神经元(中枢神经系统外)与出生后LHRH神经元 (在中枢神经系统)是使用鼻部外植体和器官类型进行研究的 文化，分别。LHRH神经元表达GABA受体和 GABA能神经元存在于鼻区。在体外，迁移 LHRH神经元的作用是：a)被GABA激动剂抑制，b)增加 由GABA拮抗剂和河豚毒素治疗。我们 假设GABA能信号调节进入的时间 LHRH神经元进入中枢神经系统。考察N-的作用 糖基化对LHRH发育的影响，我们发现衣霉素 治疗极大地改变了嗅轴突的生长- 在嗅觉小窝(OP)之间穿行的纤维，而不是离开 当到达中线组织时，进行外植体移植。虽然产生的结果是 嗅轴突改变，治疗没有破坏关联 LHRH神经元及其轴突通路，以及LHRH的运动 来自OP的神经元，表明其分子机制(S) 这些事件的基础是独立于N-糖基化的。 中线/作业关系的处理证实了导航 表达了嗅轴突适当定位的信号(S) 通过软骨中线组织。调查两国之间的关系 在基因表达、生物合成和分泌之间，我们检查了 多巴胺能神经元的mRNA周转率与LHRH 神经元。酪氨酸羟解酶与多巴胺标志物的差异 神经元)m RNA周转率在下丘脑 DA群体，弓形神经元表现出TH mRNA 与已知节奏相对应的周转率(6-7小时) 这些神经元所显示的输出。LHRH神经分泌是 搏动性(约1小时)。为了保持这一脉动特征，我们 假设LHRH信使核糖核酸迅速衰退。我们决定 LHRH信使核糖核酸快速衰变(5-13分钟)，随后 衰变速度要慢得多(329-344分钟)。值得注意的是，快速腐烂 LHRH信使核糖核酸率与LHRH快速衰减率相对应 脉搏。通过比较哺乳动物LHRH mRNAs的3‘非编码区，我们 确定了两个可能涉及到的保守区 观察到周转动力学。目前，我们正在确定：1) 影响嗅轴突生长的中线线索；2) 促肾上腺皮质激素释放激素神经元与神经元相互作用的分子本质 它们的轴突途径；3)选择性表达的基因 迁移的LHRH神经元；4)甘丙素表达细胞的关系 与LHRH神经元的分化和/或迁移有关；5) 与LHRH mRNA快速转换相关的因素。

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.