Development of the GnRH neuronal network and effects of prenatal androgen exposure

项目摘要 促性腺激素释放激素（GnRH）神经元形成调节生育力的最终共同中枢通路。 适当模式的GnRH释放是生育所必需的，在多囊卵巢妇女中经常被破坏 综合征（PCOS）。高雄激素性PCOS影响约8-10%的女性。在这些女人身上， 高频率的促黄体生成激素（LH）和可能的GnRH释放。产前雄激素化（PNA）小鼠 具有与PCOS女性相似的神经内分泌表型，包括高LH脉冲频率， 用于研究这种增加的机制。与PCOS相似的病理生理学在年轻人中被检测到。 年龄，这表明这种疾病的前身可能是发展编程。以前工作中 我们通过不同的资助机制（NCTRI）描述了GnRH神经元活性的发展特征， GABA传输到这些细胞，表明PNA破坏青春期前的两个参数，并且PNA- 青春期前后的诱发变化是不同的。这些现象背后的神经生物学机制 观察结果在很大程度上是未知的。我们的工作模型来解释这些发现是，1）PNA改变了 GnRH神经元及其传入的生物物理特性; 2）至少部分改变了表观遗传编程 3）PNA在青春期前增加兴奋性GABA对GnRH神经元的突触驱动 这种增加在成年人中继续; 4）在PNA小鼠青春期前，GnRH神经元开始内在变化， 以适应增加GABA驱动，并减少放电输出; 5）PNA小鼠的发育变化 导致这些GnRH神经元适应失败，因此在PNA成人中，增加的GABA驱动有助于 增加GnRH神经元放电; 6）增加的神经内分泌驱动增加雄激素，这是至关重要的 维持成年人的神经内分泌PNA表型。我们将在两个目标中测试这个模型。目标1将确定 PNA小鼠GnRH神经元青春期前适应GABA驱动增强的机制。 目的2将描述发育过程中GnRH神经元的表观遗传景观，以及诱导的变化 的PNA。卵巢和雄激素替代在建立和维持表观遗传变化中的作用 也将被评估。初步数据表明，GnRH神经元动作电位放电，钙电流和 与对照组相比，青春期前与成年PNA小鼠中钾电流的调节均不同。到 作为电生理学研究的补充，我们已经将表观遗传学分析应用于从一些 数百个神经元和建立的荧光细胞分选方案，产生足够数量的富集的 用于这些分析的GnRH神经元。因此，我们可以研究分子和生物物理 在PNA小鼠中观察到的GnRH神经元的功能变化的基础。这项工作将提供 目前缺乏对GnRH神经元典型功能发育的机制性认识， 青春期过程，相关的表观遗传变化，以及这些参数如何可能改变， 高雄激素性疾病;不可能从人类研究中获得这些见解。

Project Summary Gonadotropin-releasing hormone (GnRH) neurons form the final common central pathway regulating fertility. Properly patterned GnRH release is required for fertility and is often disrupted in women with polycystic ovary syndrome (PCOS). Hyperandrogenic PCOS affects ~8-10% of women. In these women, there is a persistent high frequency of luteinizing hormone (LH), and likely GnRH, release. Prenatally androgenized (PNA) mice have neuroendocrine phenotypes similar to women with PCOS, including high LH pulse frequency, and can be used to study mechanisms of this increase. Pathophysiology similar to PCOS is being detected at younger ages, suggesting the antecedents of this disorder may be developmentally programmed. In the previous work from a different funding mechanism (NCTRI), we characterized the development of GnRH neuron activity and GABA transmission to these cells, showing that PNA disrupts both parameters before puberty, and that PNA- induced changes before and after puberty are different. The neurobiological mechanisms underlying these observations are largely unknown. Our working model to explain these findings is that 1) PNA alters the biophysical properties of GnRH neurons and their afferents; 2) altered epigenetic programing at least in part underlies these changes; 3) PNA increases excitatory GABA synaptic drive to GnRH neurons before puberty and this increase continues in adults; 4) before puberty in PNA mice, GnRH neurons initiate intrinsic changes to adapt to the increased GABA drive, and firing output is reduced; 5) developmental changes in PNA mice lead to failure of these GnRH neuron adaptations, so that in PNA adults, increased GABA drive contributes to increased GnRH neuron firing; 6) the increased neuroendocrine drive increases androgens, which are critical to maintain neuroendocrine PNA phenotypes in adults. We will test this model in two aims. Aim 1 will identify the mechanisms underlying prepubertal adaptation of GnRH neurons in PNA mice to increased GABA drive. Aim 2 will characterize the epigenetic landscape in GnRH neurons during development, and changes induced by PNA. The role of the ovary and androgen replacement in establishing and maintaining epigenetic changes will also be assessed. Preliminary data indicate that GnRH neuron action potential firing, calcium currents and potassium currents are all differentially regulated in prepubertal vs adult PNA mice compared to controls. To complement the electrophysiology studies, we have adapted epigenetic profiling to libraries made from a few hundred neurons and established fluorescent cell sorting protocols that yield sufficient numbers of enriched GnRH neurons for these analyses. We are thus positioned to examine the molecular and biophysical underpinnings of the functional changes of GnRH neurons observed in PNA mice. This work will provide mechanistic insight currently lacking on the typical functional development of GnRH neurons through the pubertal process, associated epigenetic changes, and how these parameters may be altered in hyperandrogenic disorders; is not possible to obtain these insights from human studies.