New humanised mouse models for dissecting the pathobiology of disease, using FUS-ALS as a paradigm

人类和老鼠是一个共同祖先的后代，所以我们有共同的基因，并且有相似的疾病是由我们相同基因的相似突变引起的（称为同源基因）。因此，为了更多地了解人类疾病，我们使用具有相同突变并表现出类似症状的“小鼠模型”进行研究。许多神经退行性疾病作为“显性”疾病在家族中遗传，所以如果你的父母患有这种疾病，那么你有50%的机会遗传突变基因，也会死于这种疾病。这些显性疾病被称为转基因小鼠，它们携带人类突变基因，因此以与人类相似的方式患上这种疾病。转基因动物是通过将人类突变的“转基因”植入小鼠的DNA而制成的。不幸的是，当这种情况发生时，人类突变基因通常会被合并成许多拷贝，在某个相当随机的地方，而不是像人类通常那样只有一个拷贝。结果之一是，老鼠产生的突变蛋白远远超过了通常的“生理”量，而且老鼠的症状往往只是因为蛋白质过多，而不是突变的实际影响。这意味着鼠标是一个远不如它所能做到的那样精确的模型。此外，有时人类和小鼠突变蛋白的生化反应可能不同，所以简单地对小鼠基因进行相同的改变并不能产生准确的疾病模型。我们开发了一种新的小鼠模型，我们用完整的人类基因取代了小鼠基因，包括正常的人类基因和不同小鼠品系中突变的人类基因。因此，我们可以看到当人类遗传物质在正常水平上表达时，老鼠会发生什么，这将为我们了解疾病过程提供新的见解。我们的新鼠标模型可能是现有模型的改进。举个例子，我们选择研究一种叫做FUS的基因，这种基因在一种无法治愈的神经退行性疾病——肌萎缩性侧索硬化症（ALS，也称为运动神经元疾病）中发生突变。肌萎缩侧索硬化症是一种无法治愈的、无情的、毁灭性的神经退行性疾病，它会导致肌肉功能的逐渐丧失和瘫痪。在英国，ALS在确诊后平均仅3年就会导致死亡，通常是由于无法呼吸，到85岁时的终生风险约为1 / 300。ALS通常是一种中年疾病，影响40多岁和50多岁的人，尽管症状发作的年龄范围很广，并且在11岁的儿童中也有被描述为侵袭性的fus引起的ALS。FUS偶尔也会在其他无法治愈的神经系统疾病中发生突变。现在，我们正在申请一项为期三年的拨款，以：(1)扩展我们的方法，制造一种略有不同的小鼠类型，称为条件突变体，这使我们能够在不同时间在不同组织中激活突变蛋白。这将帮助我们找出ALS和其他疾病的问题所在。(2)充分表征我们新的FUS小鼠突变体，这样我们就可以更多地了解突变的FUS导致神经细胞死亡的方式。如果我们知道了这一点，我们就会在ALS和其他神经退行性疾病的治疗上更进一步。我们的技术可以用于任何基因，而不仅仅是FUS，例如，我们很好地将这种方法用于SOD1，这是另一种“ALS基因”。因此，我们开发了一项新技术，我们相信它将被其他实验室广泛使用，我们希望对我们已经培育出来的老鼠进行特征描述，以便更多地了解神经变性是如何发生的，这样我们就能更好地了解人类疾病以及如何治疗它。

Humans and mice are descended from a common ancestor and so we share genes and have similar diseases caused by similar mutations in our equivalent genes (known as orthologs). Therefore to understand more about human disease we work with 'mouse models' that have the same mutations and manifest similar symptoms. Many neurodegenerative diseases run in families as 'dominant' diseases, so if your parent has the disorder there is a 50% chance you will inherit the mutant gene, and also succumb to the disease. These dominant disorders are modelled by mice called transgenics, which carry human mutant genes and so get the disease in a similar way to humans.Transgenic animals are made by incorporating the human mutant 'transgene' into the mouse DNA. Unfortunately when this happens the human mutant gene is usually incorporated in lots of copies, somewhere fairly random, not just a single copy as it would be normally in humans. One result is the mouse produces considerably more than the usual 'physiological' amount of mutant protein, and more often than not the mouse develops symptoms that simply come from having too much protein, rather than the actual effects of the mutation. This means the mouse is a far less accurate model than it could be.Also, sometimes the human and mouse biochemistry of the mutant protein can be different, so simply making the same change in the mouse gene does not produce an accurate disease model.We have developed a new type of mouse model in which we replace the mouse gene with the complete human gene, both the normal human gene and the mutated human gene in different mouse strains. Therefore we can look at what happens to the mouse when the human genetic material is expressed at normal levels, and this will give us new insight into disease processes. Our new mouse models may be a Refinement of existing models.As an example, we have chosen to work with a gene called FUS, which is mutated in an untreatable neurodegenerative disease called amyotrophic lateral sclerosis (ALS, also known as motor neuron disease). ALS is an incurable and relentless devastating neurodegenerative disorder which causes progressive loss of muscle function and paralysis. ALS leads to death, usually caused by the inability to breathe, on average only 3 years after diagnosis, with a lifetime risk of ~1 in 300 by 85 years old, in UK. ALS is generally a mid-life disease affecting people in their 40s and 50s although there is a wide age-range of symptom onset and aggressive FUS-caused ALS has been described in children as young as 11 years old. FUS is also occasionally mutated in other incurable neurological diseases.Now we are applying for a three year grant to:(1) extend our method to make a slightly different type of mouse called a conditional mutant, which allows us to turn the mutant protein on in different tissues at different times. This will help us work out what goes wrong in ALS and other disorders. And,(2) to fully characterise our new FUS mouse mutants, so we can learn more about the way that mutant FUS causes nerve cells to die. If we know this, we are step further along to therapies for ALS and other neurodegenerative diseases.Our technology can be used for any gene, not just FUS and for example, we are well along with using this method for SOD1, which is another 'ALS gene'. So we have developed a new technology that we believe will be widely used by other laboratories, and we want to characterise the mice we have already created to understand more of how neurodegeneration happens, so that we can better understand human disease and how to treat it.