Dissection of a novel molecular pathway involved in seasonal timing in a melatonin-target tissue using an experimental and systems-level approach.

使用实验和系统级方法剖析涉及褪黑激素目标组织季节性计时的新分子途径。

• 批准号: BB/G003033/1
• 负责人: Andrew Loudon
• 金额: $ 99.43万
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FG003033%2F1
• 关键词: Dissection; novel; molecular; pathway; involved

Most species of wild animal and many of man's domesticated species are adapted to live in seasonal environments and experience significant annual changes in food supply and temperature. It is essential that seasonal animals time the onset of breeding and lay down and store fat at the appropriate time of year. In order to achieve this, they operate a seasonal clock which controls timing of many hormone rhythms. A key hormone regulating this seasonal timer is called Melatonin, which is produced within the brain in the pineal gland. Melatonin is secreted at night and the pattern of secretion changes seasonally, with longer-duration profiles produced on the long winter nights. It is known that these changes in seasonal duration drive seasonal hormone rhythms and provide the brain with an internal representation of external photoperiod change, acting on physiology and behaviour. Melatonin acts on a specialised structure called the pars tuberalis (PT) located in the pituitary gland, in a region close to the hypothalamus in the base of the brain. The PT is thought to regulate seasonal rhythms of prolactin secretion by secreting a local factor which acts on prolactin-secreting cells in the distal pituitary tissue. It also produces a hormone locally, called thyroid stimulating hormone (TSH), which we now suspect acts on TSH receptors on cells called tanycytes in the immediate hypothalamus. Here it regulates activity of key enzymes controlling thyroid hormone activity. By this means, the PT may act both on the pituitary and also the hypothalamus. We have discovered a group of genes in the PT which become active when the PT is exposed to long-duration melatonin signals on short daylengths and are also directly responsive to melatonin. These genes act on pathways which are crucial for thermogenesis, and controlling the synthesis and use of stored fat reserves. Our work aims to establish how these 'metabolism' genes may be used in this seasonal timing structure to control annual hormone rhythms. In order to monitor output, we focus on the hormone prolactin, where we can measure activity by culturing with PT cells, and on TSH production, which we can measure by assay or measures of gene expression. The goal is to work out how the melatonin signal acting on the PT drives genetic pathways which result in activation of these two hormone pathways. Finally, we have discovered that another group of genes previously known to be involved in development of many tissues including hormone secreting cells are also activated in the PT in response to daylength change. We suspect that these 'developmental' genes are linked to the metabolic pathway genes above. Our study will use several different techniques, and for much of the work we will use sheep. The reason is that the sheep PT is easy to undertake anatomical studies and can be cultured in the laboratory, allowing us to test which metabolic pathway genes may be involved in hormone regulation. First, we will describe in detail changes in activity of the metabolic and developmental genes in the PT and how they change, both with season, and when animals are exposed to abrupt changes in daylength and melatonin. We will then go on to study how proteins in the PT interact with one another, and also with DNA. This will ultimately allow us to describe a 'circuit diagram' within a melatonin-target cell and describe how genes may be activated or suppressed by melatonin. We will use the culture system to see whether changes in the melatonin signal result in altered hormone output, by measuring TSH activity (direct measure) and action on prolactin-secreting cells (in-direct measure). We will also use laboratory rodents (hamsters and rats) as here we can more easily administer drugs which act on the 'metabolic' pathway genes and see whether we see changes in hormone secretion. A final advantage to using hamsters is that we will be able to check results from sheep in a different type of seasonal breeder.

大多数野生动物物种和许多人类驯化的物种都适应生活在季节性环境中，并且经历了食物供应和温度的重大年度变化。季节性动物必须在一年中适当的时间开始繁殖，并在适当的时间下床和储存脂肪。为了达到这个目的，他们操作一个控制许多激素节律的季节性时钟。调节这种季节性计时器的一种关键激素叫做褪黑激素，它是在大脑的松果体中产生的。褪黑素在夜间分泌，分泌模式随季节变化，在漫长的冬夜产生的持续时间更长。众所周知，这些季节性持续时间的变化驱动了季节性激素节律，并为大脑提供了外部光周期变化的内部表征，作用于生理和行为。褪黑素作用于脑垂体中一个叫做结节部（PT）的特殊结构，它位于大脑底部靠近下丘脑的区域。PT被认为通过分泌一种局部因子来调节催乳素分泌的季节性节律，这种局部因子作用于垂体远端组织中的催乳素分泌细胞。它还会在局部产生一种叫做促甲状腺激素（TSH）的激素，我们现在怀疑这种激素会作用于下丘脑直接区一种叫做tanycytes的细胞上的TSH受体。它调节控制甲状腺激素活性的关键酶的活性。通过这种方式，PT可以作用于脑垂体和下丘脑。我们已经发现了一组PT中的基因，当PT在短时间内暴露于长时间褪黑激素信号时，这些基因变得活跃，并且对褪黑激素也有直接反应。这些基因作用于对产热至关重要的途径，并控制储存脂肪储备的合成和使用。我们的工作旨在确定这些“代谢”基因如何在这种季节性时序结构中使用，以控制年度激素节律。为了监测输出，我们关注催乳素激素，我们可以通过培养PT细胞来测量活性，以及TSH的产生，我们可以通过检测或基因表达来测量。我们的目标是弄清楚褪黑激素信号是如何作用于PT驱动基因通路的，从而导致这两种激素通路的激活。最后，我们发现另一组先前已知与许多组织（包括激素分泌细胞）的发育有关的基因也在PT中被激活，以响应白昼长度的变化。我们怀疑这些“发育”基因与上述代谢途径基因有关。我们的研究将使用几种不同的技术，其中大部分工作将使用绵羊。原因是羊PT容易进行解剖研究，可以在实验室培养，让我们可以测试哪些代谢途径基因可能参与激素调节。首先，我们将详细描述PT中代谢和发育基因活性的变化，以及它们是如何随季节变化的，以及当动物暴露于白昼长度和褪黑激素的突然变化时。然后我们将继续研究PT中的蛋白质如何相互作用，以及如何与DNA相互作用。这将最终使我们能够描述褪黑激素靶细胞内的“电路图”，并描述褪黑激素如何激活或抑制基因。我们将通过测量TSH活性（直接测量）和对泌乳素分泌细胞的作用（间接测量），使用培养系统来观察褪黑激素信号的变化是否会导致激素输出的改变。我们还将使用实验室啮齿类动物（仓鼠和大鼠），因为在这里我们可以更容易地给药，作用于“代谢”途径基因，看看我们是否看到激素分泌的变化。使用仓鼠的最后一个好处是，我们将能够在不同类型的季节性饲养员中检查绵羊的结果。

项目成果

Identification of Eya3 and TAC1 as long-day signals in the sheep pituitary.

• DOI: 10.1016/j.cub.2010.02.066
• 发表时间: 2010-05-11
• 期刊: Current biology : CB
• 作者: Dupré SM;Miedzinska K;Duval CV;Yu L;Goodman RL;Lincoln GA;Davis JR;McNeilly AS;Burt DD;Loudon AS
• 通讯作者: Loudon AS