Elucidating the Cep135 - CPAP- STIL protein interaction network behind primary microcephaly and centriole formation

原发性小头畸形症是一种遗传性疾病，其特征是出生时脑体积变小和智力低下。在一些人群中，每10,000人中就有1人发生这种疾病，但重要的是，它是我们可以直接追踪单个突变对大脑发育和认知功能影响的少数几种疾病之一。因此，事实证明，原发性小头症病例在识别关键的大脑发育因素方面具有启发性，而这些因素并不存在后备系统。中心体是人类细胞中的小细胞器，它组织了一个由细丝(称为微管)组成的网络，对细胞的生长、复制、移动和感知周围环境是必不可少的。中心体缺陷被认为与小头畸形有关。已知的导致这种疾病的九个基因中有五个对应于中心体成分，其中包括三种已知对这些细胞器的形成至关重要的蛋白质。除了小头畸形，中心体缺陷也是多种人类疾病的诱因，包括男性不育症、纤毛病和可能的癌症。因此，了解中心体是如何形成的是一个重要的生物学问题，具有直接的医学意义。在过去的几年里，我们的团队和其他人已经展示了单一蛋白质SAS-6是如何形成中心体建立在其上的初始框架的。对这一理解至关重要的是生物物理、结构和细胞生物学工具的组合，这些工具使我们能够分析基本蛋白质的形状，设想这些蛋白质如何连接形成分子机器，并在人类细胞中测试这些见解。在这里，我们建议通过研究与中心体初始框架相关的三个蛋白质组分(Cep135、CPAP和STIL)来建立我们对中心体初始框架的理解。我们之所以选择这些成分，是因为它们对中心体是必不可少的，它们似乎彼此相连，并与SAS-6有关，重要的是，它们都与初级小头畸形症直接相关。我们相信，了解这三种蛋白质的作用也将使我们了解正常细胞中中心体是如何形成的，以及中心体缺陷是如何导致严重疾病的。我们预计这些结果将为未来如何治疗此类疾病奠定基础。我们团队在追求这一项目所需的生物物理和结构生物学方法方面拥有长期经验。然而，我们并不仅仅依靠我们的核心能力。我们了解中心体结构的目标是与牛津大学和国外享誉国际的团体分享的，我们与他们合作。我们的实验室网络提供了尽可能广泛的技术专长基础，因此是确定中心体如何形成的最大希望。

Primary microcephaly is a hereditary disease characterised by reduced brain size from birth and mental retardation. It occurs in ~1 in 10,000 individuals in some populations, but, importantly, it is one of few diseases where we can directly trace the effects of single mutations to brain development and cognitive functions. As a result primary microcephaly cases have proved instructive in identifying crucial brain development factors for which no backup systems exist.Centrosomes, are small organelles in human cells that organise a network of thin filaments (known as microtubules) that are essential for cells to grow, duplicate, move and sense their surroundings. Defects in centrosomes have been implicated in microcephaly. Five out of nine genes known to cause the disease correspond to centrosome components, and these include three proteins known to be essential for the formation of these organelles. In addition to microcephaly, centrosomal defects are causative agents for multiple human medical conditions, including male sterility, ciliopathies and possibly cancer. Thus, understanding how centrosomes form is an important biological question with direct medical relevance.Over the last few years our group, and others, have shown how a single protein, SAS-6, forms the initial framework onto which centrosomes are build. Crucial to this understanding was a combination of biophysical, structural and cell biology tools that allowed us to analyse the shape of essential proteins, envision how such proteins might join to form molecular machines, and test these insights in human cells. Here, we propose to build upon our understanding of the initial centrosomal framework by studying three protein components (Cep135, CPAP and STIL) that link to it. We have selected these components because they are essential for centrosomes, they appear to be connected to one another and to SAS-6, and importantly, they are all directly implicated in primary microcephaly. We believe that understanding the role of these three proteins will also inform us on how centrosomes are formed in normal cells and how defects in them cause severe diseases. We expect that these results will underpin future efforts on how to treat such diseases.Our group has long experience in the biophysical and structural biology methods necessary for the pursuit of this project. However, we do not rely on our core competencies alone. Our goal of understanding the centrosome structure is shared with internationally acclaimed groups in Oxford and abroad, with whom we collaborate. Our network of laboratories provides the broadest possible base of technical expertise and, thus, the best hope for determining how centrosomes form.