Oocyte polarity and BMP-mediated dorsoventral patterning

骨形态发生蛋白（BMP）信号传导指导多个器官和组织的发育， 是多种先天性和成人疾病的致病因素，包括心血管疾病 和肢体缺陷、肾脏疾病、肺动脉高压，并且在医学应用中是重要的， 整形外科、牙髓病学和组织工程学。BMP异二聚体已经显示出一致的 对BMP同源二聚体具有更高的信号传导活性，因此开始用于治疗。理解 BMP异源二聚体如何在某些情况下更有效地或排他地发出信号，将导致它们的更多 成功应用于组织工程、骨修复和再生等领域。斑马鱼提供了一种 在背腹侧胚胎轴上的图案细胞中的排他性BMP异二聚体信号传导的范例， 一种形态素，不同的水平指定不同的细胞类型。将利用此上下文来测试 BMP异二聚体更有效的信号转导的假说。多种BMP细胞外调节剂 在胚胎中时空调节其水平。使用Smad 5的磷酸化（P-Smad 5）作为直接的 BMP信号的读出，一种定量方法将用于确定这些细胞外因子如何形成 空间和时间上的信号梯度。P-Smad 5如何将梯度转化为不同的基因表达 还将涉及指定细胞命运的结构域。在大多数脊椎动物中，卵的极性决定了 胚胎的前-后极性，是建立胚胎背-腹轴所必需的。蛋 极性起源于卵子发生的早期阶段，当不同的动物-植物域建立时， 卵母细胞脊椎动物卵母细胞中的第一个极化结构是Balbiani体（Bb），一个大的无膜的细胞核， 从昆虫到哺乳动物在青蛙和鱼中保守的结构由核糖核蛋白，ER， 高尔基体，线粒体的富集，和RNA注定卵母细胞和卵子的植物极。BB是 一种在卵母细胞皮层分离的短暂结构，传递其内容物并决定植物生长 柱尽管脊椎动物卵母细胞极性是形成大多数脊椎动物胚胎主轴的基础， 由于卵巢内这些早期卵母细胞阶段的不可接近性和难以 成年女性的基因分析。通过对斑马鱼的突变筛查，发现了两个基因， 建立卵母细胞极性、Bucky球（布克）和MacF 1（微管肌动蛋白交联因子1）。需要布克 形成Bb，而Macf 1，一个非常大的细胞骨架连接蛋白，是其解离所必需的。 布克是一种高度无序的蛋白质，在体外可以经历相变形成淀粉样纤维。的 将研究这些蛋白质在聚集Bb和解离Bb中的作用。两名新确认的Bb居民 将研究蛋白质在Bb形成及其解离中的功能。重要的是，不合适 细胞中的淀粉样蛋白聚集体是神经变性疾病的标志。因此，这些研究 与理解这些聚集体如何形成以及如何在治疗中解离有关。

Bone Morphogenetic Protein (BMP) signaling directs the development of multiple organs and tissues in embryogenesis, and is the causative factor in multiple congenital and adult diseases, including cardiovascular and limb defects, kidney disease, pulmonary hypertension, and is important in medical applications such as orthopedics, endodontics, and tissue engineering. BMP heterodimers have been shown to exhibit consistently higher signaling activity to BMP homodimers and thus are beginning to be used in therapeutics. Understanding how BMP heterodimers signal more effectively or exclusively in some contexts, will lead to their more successful use in applications like tissue engineering, bone repair and regeneration. The zebrafish offers a paradigm of exclusive BMP heterodimer signaling in patterning cells across the dorsoventral embryonic axis as a morphogen, with different levels specifying distinct cell types. This context will be exploited to test hypotheses for the more effective signaling by BMP heterodimers. Numerous extracellular modulators of BMP regulate its levels spatiotemporally in the embryo. Using phosphorylation of Smad5 (P-Smad5) as a direct readout of BMP signaling, a quantitative method will used to determine how these extracellular factors shape the signaling gradient in space and time. How P-Smad5 translates the gradient into distinct gene expression domains that specify cell fate will also be addressed. In most vertebrates, polarity of the egg determines anterior-posterior polarity of the embryo and is essential to establishing the embryonic dorsal-ventral axis. Egg polarity originates during early stages of oogenesis when distinct animal-vegetal domains are established in the oocyte. The first polarized structure in vertebrate oocytes is the Balbiani body (Bb), a large, membrane-less structure conserved from insects to mammals that in frogs and fish is composed of ribonucleoproteins, ER, golgi, an enrichment of mitochondria, and RNAs destined to the vegetal pole of the oocyte and egg. The Bb is a transient structure that dissociates at the oocyte cortex delivering its contents and determining the vegetal pole. Although fundamental to forming the major axes of most vertebrate embryos, vertebrate oocyte polarity has been little studied due to the inaccessibility of these early oocyte stages within the ovary and the difficulty of genetic analysis in adult females. Through a mutant screen in the zebrafish, two genes were discovered that establish oocyte polarity, bucky ball (buc) and macf1 (microtubule actin crosslinking factor 1). Buc is required to form the Bb, whereas Macf1, an unusually large cytoskeletal linker protein, is required for its dissociation. Buc is a highly disordered protein that can undergo a phase transition to form amyloid-like fibers in vitro. The role of these proteins in aggregating the Bb and dissociating it will be studied. Two newly identified Bb resident proteins will be investigated for their functions in Bb formation and its dissociation. Importantly, inappropriate amyloid protein aggregates in cells are hallmarks of neurodegenerative disease. Thus, these studies are relevant to understanding how these aggregates form and can be dissociated in therapeutics.