Nutrient sensing O-GlcNAcylation in pituitary development

 描述（由申请人提供）：由于全球糖消费量增长的趋势，确定饮食与产前和产后发育之间的相互作用正在成为后代的关键领域。目前，美国人平均每天吃大约22茶匙的添加糖（大约30块方糖/天隐藏在食物中）。这种富含葡萄糖的现代饮食与肥胖、糖尿病和其他代谢综合征的患病率增加有关。因此，了解糖代谢时会发生什么对公众健康至关重要。O-GlcNAc酰化是饮食响应信号的关键组成部分之一。这种独特的葡萄糖变阻器是细胞内蛋白质普遍存在的动态翻译后修饰。两种关键酶驱动O-GlcNAc循环：O-GlcNAc转移酶添加修饰，O-GlcNAc酶（OGA）去除修饰。由于这种翻译后修饰直接依赖于葡萄糖输入，消耗OGA会产生人为的和恒定的高血糖诱导的O-GlcNAc化状态。我们的实验室已经开发了Oga敲除（KO）细胞和小鼠模型，我们可以用它来破译高碳水化合物浓度对胚胎发育的影响。我的初步数据强烈支持O-GlcNAc酰化作为一个传感器的糖水平的关键信号通路在胚胎发生。事实上，Oga脑KO小鼠表现出发育延迟，这在成年动物中是明显的。我们还发现了垂体发育的显著延迟，这可能对关键的胎儿激素分泌产生影响。在Oga KO中观察到OTX 2的失调，OTX 2是一种对垂体发育至关重要的同源框蛋白。基于我们的初步数据，我们假设过量的O-GlcNAc酰化主要通过修饰OTX 2功能和网络影响垂体前叶的发育，并引发严重的发育缺陷。使用我们的模型系统，我们将定义O-GlcNAc循环在神经内分泌系统发育中的参与，该系统支持适当的身体发育。我们将首先评估O-GlcNAc化对垂体发育和随后的激素分泌（K99）的影响，重点是OTX 2表达、加工和活性。同时，我们将以垂体谱系特异性方式靶向Oga KO，以观察分泌细胞特异性作用。在本项目的第二部分（R 00）中，我们将通过O-GlcNAc酰化来确定高糖摄入对神经内分泌功能的影响。考虑到这一目标，我们将怀孕小鼠喂以高碳水化合物饮食，并分析产前和产后发育，观察果糖和/或葡萄糖对O-GlcNAc酰化和OTX 2功能的影响。最后，我们将体外补剂小鼠与体外补剂小鼠进行区分， 在不同营养条件下分化的垂体细胞。我们建议在分析、解释和治疗神经内分泌病理学（如发育迟缓和神经内分泌肿瘤）时，需要考虑O-GlcNAc化。此外，这项研究将是一种新的方法来了解饮食如何影响胚胎发育期间以及以后的生活中的激素分泌。

 DESCRIPTION (provided by applicant): Due to the trend of global growing sugar consumption, determining the interplay between diet and pre- and post-natal development is emerging as a critical area for future generations. Currently, the average American eats around 22 teaspoons of added sugar every day (~30 sugar cubes/day hidden in foods). This modern glucose-rich diet correlates with an increase in the prevalence of obesity, diabetes and others metabolic syndromes. Therefore, understanding what happens when sugars are metabolized will be of utmost importance for public health. O-GlcNAcylation is one of the key components of diet-responsive signaling. This unique glucose rheostat is a ubiquitous and dynamic post-translational modification of intracellular proteins. Two key enzymes drive O- GlcNAc cycling: the O-GlcNAc transferase adds the modification and the O-GlcNAcase (OGA) removes it. Because this post-translational modification is directly dependent on glucose input, depleting OGA creates an artificial and constant hyperglycemia-induced O-GlcNAcylation state. Our lab has developed Oga knockout (KO) cellular and mouse models, which we can use to decipher the impact of high carbohydrate concentration on embryonic development. My preliminary data strongly supports that O-GlcNAcylation acts as a sensor of sugar levels for key signaling pathways during embryogenesis. In fact, the Oga brain KO mice exhibit a developmental delay, which is noticeable in adult animals. We have also uncovered a striking delay in pituitary development that likely has consequences on key fetal hormones secretion. Deregulation of OTX2, a homeobox protein critical for pituitary development, has been observed in the Oga KO. Based on our preliminary data, we hypothesize that the excess O-GlcNAcylation impacts the development of the anterior pituitary, by principally modifying OTX2 functions and networks, and triggers severe developmental defects. Using our model systems, we will define the involvement of O-GlcNAc cycling in the development of the neuroendocrine system, which supports proper body development. We will first assess the impact of O- GlcNAcylation on pituitary development and the subsequent hormone secretion (K99), focusing on OTX2 expression, processing, and activity. In parallel, we will target Oga KO in a pituitary-lineages-specific manner to observe secretory-cell specific effect. In the second part of this project (R00), we will define the influece of high sugar consumption on neuroendocrine function through O-GlcNAcylation. This goal in mind, we will pregnant mice to a high carbohydrate diet and analyze pre- and post-natal development and observe the impact of fructose and/or glucose on O-GlcNAcylation and OTX2 functions. Finally, we will differentiate in vitro supplement mice hormone-deficiency with in vitro differentiated pituitary cells under varied nutrient conditions. We are suggesting that O-GlcNAcylation needs to be taken into account when analyzing, deciphering and treating neuroendocrine pathologies like developmental delay and neuroendocrine tumors. Moreover, this study will be a new approach to understand how diet impacts hormone secretion during embryonic development as well as later in life.