Sympathetic innervation in pancreatic development and function

描述(申请人提供)：已知的自主神经系统通过调节成人胰腺中的激素释放来调节葡萄糖的稳态。朗格汉斯人的胰岛由自主神经系统的交感神经丰富地支配，神经支配的起始时间与发育中的胰岛的生长和成熟阶段相吻合。然而，交感神经是否参与了胰腺器官的发生至今还没有明确的定义。我们最近报道，在小鼠的发育过程中，切除交感神经会导致胰岛形状和细胞结构的严重缺陷(Borden et.Al，2013)。交感神经切除的小鼠在以后的生活中表现出胰岛素分泌减少和葡萄糖耐受性降低。因此，这项建议的总体目标是阐明交感神经元促进胰岛形成和获得功能成熟的分子机制。根据初步发现，我们假设神经源性信号是神经递质去甲肾上腺素，它通过胰腺�-肾上腺素能受体作用于促进�细胞迁移和胰岛组织。因此，我们将通过评估缺乏去甲肾上腺素能神经传递的突变小鼠体内的胰岛形成，以及通过检测去甲肾上腺素对体外�细胞迁移和聚集的影响来确定去甲肾上腺素对胰岛构建是否必要和充分(目标1)。在目标2中，我们将确定去甲肾上腺素信号影响胰岛构筑的分子机制。通过对交感神经切除的胰岛进行深度测序，我们观察到Pttg1(垂体肿瘤转化基因1)的显著下调，Pttg1编码一种据报道具有细胞骨架调节功能的蛋白质。因此，我们将确定Pttg1是否是去甲肾上腺素信号的转录靶点。此外，我们将利用现有的Pttg1基因敲除小鼠来评估Pttg1是否是�细胞迁移的重要调节因子。最后，我们将通过研究去甲肾上腺素对�细胞的葡萄糖敏感机制和胰岛素颗粒运输的影响来阐明神经衍生信号影响胰岛成熟的机制(目标3)。我们的研究的意义在于，它是第一个解决神经系统如何控制胰岛发育的问题，并将在目前治疗胰腺功能障碍的翻译努力中开启一条新的研究路线。

DESCRIPTION (provided by applicant): The autonomic nervous system is known to regulate glucose homeostasis by modulating hormone release in the adult pancreas. Pancreatic islets of Langerhans are richly innervated by sympathetic nerves of the autonomic nervous system and the onset of innervation is coincident with stages of islet growth and maturation in the developing pancreas. Yet, whether, sympathetic innervation contributes to pancreas organogenesis has not been defined so far. We recently reported that ablation of sympathetic nerves results in profound defects in the shape and cyto-architecture of islets during development in mice (Borden et. al, 2013). Sympathectomized mice exhibit reduced insulin secretion and glucose intolerance later in life. Thus, the overall goal of this proposal is to elucidate the molecular mechanisms by which sympathetic neurons promote islet formation and the acquisition of functional maturity. Based on preliminary findings, we hypothesize that the nerve-derived signal is the neurotransmitter, norepinephrine, that acts via pancreatic �-adrenergic receptors to promote �-cell migration and islet organization. Thus, we will determine if norepinephrine is necessary and sufficient for islet architecture by assessing islet formation i vivo in mutant mice that lack noradrenergic neurotransmission, as well as by examining the effects of norepinephrine on �-cell migration and aggregation in vitro (Aim 1). In Aim 2, we will identify the molecular mechanisms by which norepinephrine signaling influences islet architecture. By deep sequencing-based profiling of sympathectomized islets, we observed a dramatic down-regulation of PTTG1 (pituitary tumor-transforming gene 1), that encodes for a protein reported to have cytoskeleton-regulatory functions. Thus, we will determine if PTTG1 is a transcriptional target of norepinephrine signaling. Additionally, we will assess whether PTTG1 is an essential regulator of �-cell migration, employing available PTTG1 knockout mice. Finally, we will elucidate the mechanisms by which nerve-derived signaling influences islet maturation by examining the effects of norepinephrine on the glucose-sensing machinery and insulin granule trafficking in �-cells (Aim 3). The significance of our studies is that it is the first to address how the nervous system controls islet development and will also initiate a new line of research in current translational efforts to treat pancreatic dysfunction.