Oocyte polarity and BMP-mediated dorsoventral patterning

骨形态发生蛋白(BMP)信号转导多器官组织的发育 胚胎发生，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，在医疗应用中非常重要，例如 整形外科、牙髓医学和组织工程学。BMP异源二聚体已经被证明表现出一致的 对BMP同源二聚体具有更高的信号活性，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或更专一地发出信号，将导致他们 在组织工程、骨修复和再生等应用中成功应用。斑马鱼提供了一种 BMP异源二聚体在横跨背腹胚轴的图案化细胞中的独占信号范例 一种形态生成素，具有不同的水平指定不同的细胞类型。此上下文将被用来测试 BMP异源二聚体更有效信号传递的假说。骨形态发生蛋白的多种细胞外调节剂 在胚胎中时空调节其水平。用Smad5(P-Smad5)的磷酸化作为直接 BMP信号的读数，将使用一种定量方法来确定这些细胞外因子的形状 信号在空间和时间上的梯度。P-Smad5如何将梯度转化为不同的基因表达 指定细胞命运的域也将被解决。在大多数脊椎动物中，卵的极性决定了 胚胎的前后两极，对于建立胚胎背腹轴是必不可少的。蛋 极性起源于卵子发生的早期阶段，此时不同的动植物结构域在 卵母细胞。脊椎动物卵母细胞的第一个极化结构是Balbiani小体(BB)，它是一种大的、无膜的结构 从昆虫到哺乳动物的保守结构，在青蛙和鱼中是由核糖核蛋白，内质网， 高尔基体，线粒体和RNA的丰富，最终到达卵母细胞和卵子的营养极。BB是 一种暂时的结构，在卵母细胞皮质处解离，传递其内容物并决定植物 杆子。尽管是形成大多数脊椎动物胚胎主轴的基础，但脊椎动物卵母细胞的极性 由于卵巢内这些早期卵母细胞阶段的不可及和困难，对其研究很少。 在成年女性身上进行遗传分析。通过斑马鱼的突变筛选，发现了两个基因 建立卵母细胞极性、巴基球(BUC)和MACF1(微管肌动蛋白交联素1)。BUC为必填项 形成BB，而Macf1，一种异常大的细胞骨架连接蛋白，需要它的解离。 BUC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。这个 这些蛋白质在BB聚集和解离中的作用将被研究。两名新确认的BB居民 将研究蛋白质在BB的形成和解离中的作用。重要的是，不适当的 细胞中的淀粉样蛋白聚集体是神经退行性疾病的标志。因此，这些研究是 与理解这些聚集体如何形成以及在治疗学中可以被解离有关。

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.