Mechanisms of vertebrate post-embryonic developmental progression

描述(申请人提供)：我们仍然对脊椎动物发育后期调节和同步形态发生事件的机制知之甚少。然而，了解控制这些后期发育阶段的因素对于了解成人特征是如何形成的至关重要，并将有助于洞察人类胚胎后胎儿和新生儿时期出现的形态缺陷和障碍。这项研究利用了斑马鱼，它经历了广泛的胚胎后发育，涉及许多不同器官系统的修改和成熟；这些变化中的许多与人类胚胎发生后发生的过程相似或相同。这一建议采用了几种策略来理解斑马鱼从幼体向幼体转化的潜在机制。第一个目标是采用有针对性的方法，测试甲状腺激素在胚胎后发育转变中的具体作用。多条证据表明，甲状腺激素参与了斑马鱼的几个发育过程，但这种激素影响特定的形态发生过程和细胞行为的能力尚不清楚。这一目标将测试甲状腺激素在促进全球躯体发育进程和特定的、特征良好的细胞谱系的行为方面的作用，该细胞谱系在幼虫到幼虫的转变过程中产生成体色素沉着。第二个目标是采取一种前瞻性的遗传策略，以确定胚胎后阶段转变所需的新基因。这种方法已经确定了两个突变体，它们在幼虫发育过程中表现出完全的体细胞停滞，在2周和3周大的野生型幼虫通常达到的阶段停止个体发育进程。这些表型表明胚胎后发育所必需的基因受损。绘制和克隆突变并确定它们所属的路径将揭示胚胎后发育过程所必需的机制；继续进行这一筛选将识别更多的幼虫停滞表型。最终目的是利用一种与斑马鱼有亲缘关系的物种，这种斑马鱼表现出天然的缺陷，无法执行体细胞胚胎后发育的最终阶段。主要集中在皮肤内的结构和表达，遗传和发育结构的变化将在胚胎后发育截断的背景下阐明。这些分析将揭示性状和调控途径之间的脱钩程度，以及休眠的遗传途径是否保持对胚胎后发育的关键内分泌调节因子的反应性。总体而言，这些努力将表征已知的内分泌调节因子的形态发生作用，将识别调控正常胚胎后发育的新因素，并将建立一个新的模型，以剖析发育遗传途径和内分泌机制的进化方式。此外，该项目还将完成一名具有种群生态学背景的学者的发育生物学和遗传学培训，并将为她的独立研究实验室奠定基础。

DESCRIPTION (provided by applicant): We still know very little about the mechanisms that regulate and synchronize morphogenetic events during later stages of vertebrate development. Nonetheless, understanding the factors controlling these later developmental periods is essential to understanding how adult traits form, and will lend insight into morphological defects and disorders that arise during human post-embryonic fetal and neonatal periods. This research utilizes the zebrafish, which undergoes extensive post-embryonic development involving modifications and maturation in many different organ systems; many of these changes are similar or identical to processes that occur following embryogenesis in humans. This proposal employs several strategies towards understanding the mechanisms underlying the zebrafish transformation from larva to juvenile. The first aim adopts a targeted approach, testing the specific roles of thyroid hormone in post-embryonic developmental transitions. Multiple lines of evidence indicate that thyroid hormone is involved in several developmental processes in zebrafish, but the ability of this hormone to effect specific morphogenetic processes and cellular behaviors remains unclear. This aim will test roles of thyroid hormone in promoting both global somatic developmental progression and the behaviors of a specific, well-characterized cell lineage that produces adult pigmentation during the larval-to-juvenile transition. The second aim takes a forward genetic strategy to identify novel genes required for post-embryonic stage transitions. This approach has already identified two mutants that exhibit complete somatic arrest during larval development, ceasing ontogenetic progression at stages normally reached by 2- and 3-week old wild-type larvae. These phenotypes suggest an impairment of genes absolutely required for post-embryonic progression. Mapping and cloning the mutations and characterizing the pathways to which they belong will reveal mechanisms essential for post-embryonic developmental processes; continuation of this screen will identify further larval arrest phenotypes. The final aim utilizes a species related to zebrafish that exhibits a natural failure t execute the terminal stages of somatic post-embryonic development. Focusing primarily on the structure and expression within the skin, changes in genetic and developmental architecture will be elucidated in this context of post-embryonic developmental truncation. These analyses will reveal the both extent of decoupling between traits and regulatory pathways, and whether dormant genetic pathways retain responsiveness to a key endocrine mediator of post-embryonic development. Overall, these efforts will characterize the morphogenetic roles of a known endocrine regulator, will identify novel factors that regulate normal post-embryonic progression, and will establish a novel model for dissecting the ways in which developmental genetic pathways and endocrine mechanisms can evolve. Moreover, this project will complete the developmental biology and genetics training of a scholar with a background in population ecology, and will establish the foundation for her independent research laboratory.