MICA: Identification of compounds capable of de-repressing zeta-globin in order to treat patients with severe alpha-thalassaemia

血红蛋白(Hb)是红血球中蛋白质的主要成分，它使血液呈现红色，并负责携带氧气到全身。血红蛋白由四条链组成：2条α链和2条β链。负责产生这些链的遗传密码(DNA)的突变可能会导致阿尔法链的产生减少，这种情况被称为阿尔法地中海贫血症(β链的突变，导致贝塔地中海贫血)。人类有四种阿尔法珠蛋白基因，每一种基因通常都能产生阿尔法珠蛋白。如果一个或两个基因受到突变的影响，那么就会产生没有任何症状的轻度贫血。然而，如果三个阿尔法珠蛋白基因受到影响，可能会导致严重的贫血，需要定期输血。如果所有四个阿尔法珠蛋白基因都受到影响，这意味着不能产生功能性血红蛋白，这样的患者在怀孕后大约4-6个月就会在子宫中死亡(这种情况被称为胎儿巴氏水肿症)。轻微的阿尔法地中海贫血症对疟疾这种传染病有一定的保护作用。因此，在世界某些地区，甲型地中海贫血症是非常常见的：在中国南部和香港，携带者频率为4-8%，在泰国、菲律宾和越南人口中的携带率相似，但在泰国北部最为常见，那里的人口高达14%是携带者。因此，严重的阿尔法地中海贫血是一个重大的全球健康问题，每年至少有2.6万例高危妊娠，由于移民，这现在是一个全球健康问题。目前，治疗阿尔法地中海贫血症的方法仅限于输血，偶尔还包括骨髓移植。骨髓移植可能是非常危险的，多达五分之一的患者因为这一过程本身而死亡。长期定期输血也会造成严重的医疗问题。此外，通常建议巴特氏胎儿水肿症流产，因为他们在出生前身体很不舒服。因此，我们迫切需要新的治疗方法来治疗严重形式的阿尔法地中海贫血。当婴儿发育时，他们最初会产生一条不同的珠蛋白链，类似于受孕后8周的阿尔法珠蛋白；这被称为Zeta-珠蛋白。我们知道这能够在成人中替代阿尔法-珠蛋白。然而，不幸的是，它通常会在八周后关闭。如果我们能找到一种方法在成人红细胞中重新启动它，这将治疗严重形式的阿尔法地中海贫血患者，并使他们能够过上正常的生活。在这个项目中，我们的目标是识别可以用作药物的化合物，以重新启动Zeta-珠蛋白，从而治疗严重的阿尔法地中海贫血症患者。为了帮助实现这一点，我们制造了一只小鼠，在小鼠中，Zeta-珠蛋白被一种荧光蛋白质“标记”。这意味着我们有一种灵敏而具体的方法来识别启用Zeta-珠蛋白的血细胞，因为当Zeta-珠蛋白打开时，红细胞会发光。这使得我们可以将大量不同的化合物添加到小鼠的红细胞中，并快速轻松地看到哪些化合物会导致红细胞发光。一旦我们确定了潜在的化合物，我们将确保它们也能在人类细胞中重新打开泽塔珠蛋白，并试图通过做更多的实验来了解它们是如何重新打开哲珠蛋白的。我们将与一家名为阿斯利康的制药公司合作，进行化合物的初步筛选，因为他们在开发药物方面拥有特殊的专业知识。从长远来看，我们的目标是首先在阿尔法地中海贫血症的小鼠模型中测试这些化合物，然后在人类细胞系统中测试，如果成功的话，再在人身上测试。

Haemoglobin (Hb) is the major component of the protein found in red blood cells, it gives blood its red colour and is responsible for carrying oxygen around the body. Haemoglobin is made up of four chains: 2 alpha chains and 2 beta chains. Mutations in the genetic code (the DNA) responsible for producing these chains can lead to decreased production of the alpha chains, a condition called alpha-thalassaemia (mutation of the beta-chains, causes beta-thalassemia). There are four alpha-globin genes in humans, each of which normally contributes to alpha-globin production. If one or two genes are affected by mutations, then this produces a mild anaemia without any symptoms. However, if three alpha-globin genes are affected, this can lead to a severe anaemia needing regular transfusions. If all four alpha-globin genes are affected, this means that no functional haemoglobin can be produced, and such patients die in the womb approximately 4-6 months after conception (a condition called Barts Hydrops fetalis). Mild alpha-thalassaemia provides some protection against the infectious disease malaria. In certain parts of the world, alpha-thalassaemia is therefore very common: the carrier frequency is 4-8% in Southern China and Hong Kong and at a similar level in the Thai, Filipino and Vietnamese populations, however, it is most common in Northern Thailand where up to 14% of the population are carriers. Severe alpha-thalassemia is therefore a major global health problem with at least 26,000 at-risk pregnancies annually and because of migration this is now a global health problem. At the moment, treatments for alpha-thalassaemia are limited to blood transfusion and occasionally, bone marrow transplantation. Bone marrow transplantation can be very dangerous, with up to 1/5 patients dying because of the procedure itself. Regular blood transfusions also cause serious medical problems long-term. In addition, it is normally recommended that Bart's Hydrops fetalis babies are aborted because they are so unwell prior to being born. We therefore urgently need new treatments for severe forms of alpha-thalssaemia. When babies develop, they initially produce a different globin chain, similar to alpha-globin for the first 8 weeks after conception; this is called zeta-globin. We know this is capable of substituting for alpha-globin in adults. Unfortunately however, it is normally switched off after eight weeks. If we could find a way of turning it back on in adult red blood cells, this would treat patients with severe forms of alpha-thalssaemia and could allow them to live a normal life.In this project, we aim to identify chemical compounds which could be used as medicines to switch zeta-globin back on, thereby treating patients with severe alpha-thalassaemia. To help undertake this, we have made a mouse, where zeta-globin is "tagged" by a fluorescent protein. This means that we have a sensitive and specific way of identifying blood cells where zeta-globin is turned on, as when zeta-globin is on, the red blood cell glows. This allows us to add lots of different compounds to red blood cells from the mouse, and see quickly and easily which ones cause the red blood cells to glow. Once we have identified potential compounds, we will make sure they also turn zeta-globin back on in human cells and try and understand how they are turning zeta-globin back on by doing additional experiments. We will perform the initial screen of compounds by collaborating with a pharmaceutical company called AstraZeneca, as they have particular expertise in developing medicines. Longer-term, we would aim to test the compounds, initially in mouse models of alpha-thalassaemia, then in human cellular systems and if that is successful, in people.