Development And Regulation Of The Gonadotropin Releasing Hormone System

对生殖至关重要的GnRH神经元来自鼻腔，并迁移到大脑，在那里它们成为下丘脑-垂体-性腺轴的组成部分。我们研究了GnRH神经元在正常/转基因动物和鼻腔外植体中的分化、迁移和轴突靶向的机制。使用这些相同的模型，我们的工作还解决了GnRH神经元中调节（内在和跨突触）GnRH基因表达、肽合成和分泌的机制。多种方法用于识别和理解在引导GnRH神经元到达其在中枢神经系统中的最终位置中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，在迁移路线上关键位置差异表达的分子的检查，敲除小鼠GnRH系统发育的形态学检查，以及体外分子扰动和随后监测GnRH神经元运动。随着GnRH神经元的迁移，它们也成熟了，这两个过程实际上可能是相关联的。为了研究GnRH神经元的成熟，我们使用钙成像、电生理和生化方法来检测GnRH神经元的活性和肽分泌。此外，我们还与实验室合作，对Kallman患者进行人类基因筛查。一旦发现突变，我们分析小鼠的表达模式，并进行生物学分析，以确定突变基因对GnRH发育的影响。

GnRH 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 GnRH 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) GnRH gene expression, peptide synthesis and secretion in GnRH neurons. Multiple approaches are used to identify and understand the multitude of molecules and factors which play a role in directing the GnRH 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 GnRH system in knockout mice, and perturbation of molecules in vitro and subsequent monitoring of GnRH neuronal movement. As GnRH neurons migrate they also mature and the two processes may in fact be linked. To investigate the maturation of GnRH neurons we use calcium imaging, electrophysiology and biochemical measures to examine GnRH neuronal activity and peptide secretion. In addition, we collaborate with labs performing human genetic screening of Kallman patients. Once a mutation is identified, we analyze the expression pattern in mice and perform biological assays to determine the outcome of the mutated gene on GnRH development. Over the past year, one article was published and one graduate student obtained their PhD with paper under revisions: Article) In vertebrates, Gonadotropin releasing hormone-1 (GnRH) neuroendocrine cells originate in the olfactory placode and migrate into the forebrain where they regulate reproduction. However, the embryonic lineage of their progenitors remains controversial. Most GnRH neurons are derived from placodal ectodermal progenitor cells, but data from lineage tracing in zebrafish (Whitlock et al., 2003) and mouse (Forni and Wray, 2012) indicate that some GnRH progenitor cells have a neural crest (NC) origin. In contrast, a recent study in zebrafish (Aguillon et al., 2018), using Islet-1/2 expression, identified this LIM-homeodomain protein in all developing GnRH neuroendocrine cells, and the authors concluded a homogenous origin from progenitors within the preplacodal ectoderm. Evidence in different animal models and systems suggests that expression of Islet-1 plays a pivotal role in cell fate specification and differentiation. Thus, expression of Islet-1/2 in all GnRH cells in the nasal placode may not be lineage dependent but rather initiated locally in the placode as part of the program for GnRH cell specification and/or differentiation. This study addresses this issue and shows two populations of olfactory derived GnRH neurons in embryonic mouse: Islet- 1/2(+) and Islet-1/2(-). Notably, triple-label immunofluorescence using the NC lineage tracer Wnt1, showed that GnRH neurons derived from Wnt1 progenitors are Islet-1/2(-). These results are consistent with two separate origins of GnRH neuroendocrine cells and suggest that either (1) NC-derived GnRH cells differentiate earlier than PE-derived GnRH cells or (2) different programs are used for cell specification in NC- vs. PE-derived GnRH cells. Thesis title) Neurorepair Promoting Crosstalk between Astrocytes and Olfactory ensheathing cells. This body of work addresses the signaling pathways that switch astrocytes from neurogenesis-inhibitory to neurogenesis-supportive to uncover novel approaches to reverse the progression of neurodegenerative diseases and traumatic CNS injuries.