Integration of BMP and Wnt signalling in the developing zebrafish ear

我们对内耳及其在胚胎发育过程中形成的美丽而复杂的结构着迷。对于成年人来说，这个复杂的感觉器官可以感知声音、重力和运动，使我们能够听到并保持平衡。在这个项目中，我们的目标是揭示细胞在胚胎中相互传递信号以确保内耳正确发育的机制。内耳在胚胎时期由耳囊发育而来，耳囊是靠近发育中的大脑形成的一个简单的细胞球。在胚胎发育过程中，耳囊细胞和未成熟的大脑细胞发送和接收分子信号，传递关于何时激活不同基因表达的指令。这种信号活动导致基因活动的级联，导致内耳中不同结构的正确形成。我们对指示耳囊形成半规管的信号特别感兴趣，这是在耳朵前庭（平衡）部分起作用的弯曲管道。我们将重点关注两组信号组件，即BMP和Wnt通路。我们将破坏耳朵或发育中的脑组织中这些通路中的单个蛋白质，以检查对耳朵发育的影响。我们的初步研究表明，一种被称为Bmper的蛋白质在发育中的耳朵中作为一个枢纽，整合来自两条途径的信号信息。据我们所知，这是一个尚未在任何系统中得到检验的新想法。我们在埃克塞特大学的合作者和其他人的实验室最近的研究表明，许多信号是通过细胞素传递和接收的，细胞素是细胞膜的动态薄延伸。信号分子本身被认为定位于这些膜突起的尖端。我们假设细胞素参与了向发育中的耳朵发送信号，我们研究的一部分将涉及使用高分辨率显微镜寻找这些结构和其中的信号分子。我们将使用斑马鱼胚胎作为我们的模型系统，主要有两个原因。首先，斑马鱼胚胎是光学透明的，这意味着我们可以在显微镜下看到活体胚胎的内部器官，如大脑或耳朵，而无需解剖。我们可以用荧光标记的蛋白质标记细胞，在细胞发育过程中点亮不同的结构。其次，一项被称为CRISPR干扰的新技术将使我们能够以非常精确的方式阻断耳朵或发育中的脑组织中的基因功能，而不会影响胚胎中的其他组织。我们在谢菲尔德大学的同事们正在开发这项技术，作为研究斑马鱼模型系统的社区资源，我们将在我们的项目中利用它。我们的工作旨在揭示信号分子如何指导胚胎中发育器官系统的正常形成的基本发育原理。然而，这些发现可能与医学相关：在人类中，BMP通路基因的突变是先天性遗传疾病的病因，而在生命的后期，Wnt信号通路的不适当激活是许多癌症的基础。

We are fascinated by the inner ear and the generation of its beautiful and intricate structure during embryonic development. In the adult, this complex sensory organ detects sound, gravity and motion, enabling us to hear and to maintain balance. In this project, we aim to uncover the mechanisms by which cells signal to one another in the embryo to ensure that the inner ear develops correctly.The inner ear develops in the embryo from the otic vesicle, a simple ball of cells that forms in close proximity to the developing brain. During embryonic development, cells of the otic vesicle and of the immature brain send and receive molecular signals, relaying instructions about when to activate the expression of different genes. This signalling activity results in cascades of gene activity, leading to the correct formation of different structures in the inner ear. We are particularly interested in the signals that instruct the otic vesicle to form the semicircular canals, curved ducts that function in the vestibular (balance) part of the ear.We will focus on two sets of signalling components, known as the BMP and Wnt pathways. We will disrupt individual proteins in these pathways either in ear or in developing brain tissue to examine the effects on ear development. Our preliminary studies indicate that a protein known as Bmper acts as a hub to integrate signalling information from both pathways in the developing ear. This is a new idea that has not yet been tested in any system, to our knowledge.Recent studies in the lab of our collaborator at the University of Exeter and others have shown that many signals are delivered to and received by cells on cytonemes, dynamic thin extensions of the cell membrane. The signalling molecules themselves are thought to be localised to the tips of these membrane protrusions. We hypothesise that cytonemes are involved in signalling to the developing ear, and part of our study will involve searching for these structures, and the signalling molecules within them, using high-resolution microscopy.We will use the zebrafish embryo as our model system, for two main reasons. Firstly, the zebrafish embryo is optically transparent, meaning that we can see internal organs such as the brain or ear in the live embryo under the microscope, without any need for dissection. We can label cells with fluorescently-tagged proteins, lighting up different structures as they develop. Secondly, a new technique known as CRISPR interference will allow us to block gene function in a very precise manner in either the ear or developing brain tissue, without affecting other tissues in the embryo. Our colleagues at the University of Sheffield are developing this technique as a community resource for those working on the zebrafish model system, and we will exploit this in our project.Our work aims to uncover fundamental developmental principles about how signalling molecules instruct the normal formation of a developing organ system in the embryo. However, the findings are likely to be of interest and relevance to medicine: in humans, mutations in BMP pathway genes are causative of congenital genetic disorders, while later in life, inappropriate activation of the Wnt signalling pathway underlies many cancers.