Deciphering alpha2-chimaerin signalling pathways in ocular motor development and Duane Retraction Syndrome

斜视在人类中很常见。如果病情严重，可能会导致视力减弱和部分失明，如果病情不那么严重，可能会在日常生活中，特别是在社交场合中造成虚弱。斜视是眼睛无法正确对准，现在已知是由于胎儿发育过程中神经生长错误造成的。控制眼部肌肉的一条或多条脑神经可能发育异常，导致眼球运动缺乏协调。目前唯一可用于治疗斜视的药物是弱化正常肌肉的手术(“残肢手术”)或儿童的眼罩。最近，科学证据表明，一种名为杜安退缩综合征(DRS)的斜视是由分子α2-嵌合体突变引起的。我们实验室的研究表明，α2-嵌合体是神经系统发育过程中的关键，负责脑神经到眼肌的精确导航。α2嵌合体驻留在神经元内部，对发育中的胎儿环境中的传入信号做出反应，将这些信号与神经元内部的机械连接起来，使它们能够生长、分支并连接到眼肌。为了发挥这一作用，α2-嵌合体分子是动态的，与多个其他分子伙伴相互作用。为了详细了解alpha2-嵌合体突变如何以及为什么会产生斜视，我们需要更多地了解这种分子在神经元中是如何工作的，以及它与哪些分子相互作用。我们的项目将使用强大的质谱学技术来识别与α2-嵌合体相互作用的新分子。我们将从细胞中分离嵌合体和相互作用的分子复合体，然后利用质谱学产生这种复合体的分子指纹。然后，我们将把这组分子称为信号传递模块，并将其与在人类中发现的与突变形式的α2嵌合体相互作用的分子列表进行比较和对比。斜视突变的影响之一很可能是改变神经元内α2-嵌合体及其相关分子相互作用的详细模式。这些信息将开始使我们能够剖析导致神经布线错误和眼动缺陷的过程。一旦确定了一份“候选”分子名单，就将使用复杂的生物信息学进行筛选，并利用分子定位技术确认单个分子与神经元中的α2嵌合体相关。然后，将用斑马鱼作为动物模型，对三到五个有希望的候选者进行进一步的分析。令人惊讶的是，这为人类提供了一个很好的斜视模型，因为眼睛肌肉和神经的系统是相同的，我们可以拍摄发育中的鱼的眼睛运动。因为我们知道消除斑马鱼中的α2-嵌合体功能会产生类似于人类DRS的神经线路缺陷，然后我们将把这些线路缺陷与我们操纵候选相互作用组分子的表达时产生的缺陷进行比较。如果缺陷相似，这将表明我们的新分子在眼肌连接和DRS中发挥着重要作用。进一步确定我们识别的分子的重要性将是将它们引入携带人类α2嵌合体突变的斑马鱼。由于这些突变鱼的神经连接有缺陷，眼睛运动也有缺陷，我们将通过拍摄这些鱼的眼睛运动来测试候选分子是否能恢复正常的发育和眼睛功能。这项实验的关键重要性在于，它可能精确定位一个或多个分子，这些分子可能在未来提供治疗人类斜视的方法。我们的发现将与我们的临床合作者分享，以便及时将治疗斜视的方法带到临床上。

Squint is common in humans. If the condition is severe, it can lead to weakness of vision and partial blindness, or if less severe, it can be debililitating in daily life and particularly in social situations. Squint is the failure to align the eyes correctly, and is now known to result from errors in nerve growth during development of the foetus. One or more of the cranial nerves that control the eye muscles may develop aberrantly, leading to a lack of co-ordination of eye movements. The only medical treatment currently available to treat squint is surgery to weaken a normal muscle ('mutilant surgery') or eye patching in children. Recently, scientific evidence has shown that a form of squint called Duane Retraction Syndrome (DRS) result from mutations in the molecule alpha2-chimaerin. Studies from our laboratory have shown that alpha2-chimaerin is a linchpin during development of the nervous system, being responsible for the precise navigation of cranial nerves to the eye muscles. Alpha2-chimaerin resides in the interior of neurons, and responds to incoming signals in the environment of the developing foetus, engaging these signals with the machinery inside neurons that allows them to grow, branch and connect up with the eye muscles. To perform this role, the alpha2-chimaerin molecule is dynamic, interacting with multiple other molecular partners. To understand in detail how and why alpha2-chimaerin mutations produce squint, we need to know far more about how this molecule works in the neuron, and which molecules it interacts with. Our project will use the powerful technology of mass spectrometry to identify new molecules that interact with alpha2-chimaerin. We will isolate chimaerin and the complex of interacting molecules from cells and then produce a sort of molecular fingerprint of this complex using mass spectrometry. This group of molecules which we call a signalling 'module', will then be compared and contrasted with the list of molecules that interact with mutant forms of alpha2-chimaerin found in humans. It is likely that one of the effects of squint mutations will be to change the detailed pattern of interactions of alpha2-chimaerin and its associates inside neurons. This information will start to allow us to dissect out the process that leads to faulty nerve wiring and eye movement defects.Once a list 'candidate' molecules has been identified, it will be winnowed down using sophisticated bioinformatics, and by confirming that individual molecules associate with alpha2-chimaerin in neurons using molecular localisation techniques. A group of three to five promising candidates will then be analysed further by using the zebrafish as an animal model. Surprisingly, this provides an excellent model for squint in humans, as the system of eye muscles and nerves is identical, and we can film the eye movements of the developing fish. As we know that eliminating alpha2-chimaerin function in the zebrafish produces nerve wiring defects similar to DRS in humans, we will then compare these wiring defects with those produced when we manipulate the expression of our candidate interactome molecules. If the defects are similar, this will suggest that our novel molecules play an important role in eye muscle wiring and DRS. A further step in establishing the importance of our identified molecules will be to introduce them into zebrafish which carry human alpha2-chimaerin mutations. As these mutant fish have faulty nerve wiring and defective eye movements, we will test whether the candidate molecules can restore normal development and eye function, by filming the fishes' eye movements. The key importance of this experiment is that it may pinpoint one or more molecule which might in future provide a therapy for squint in humans. Our findings will be shared with our clinical collaborators so that in time a therapy for squint may be brought to the clinic.