RUI: Neural Regulation of Metamorphosis in a Gastropod Mollusc

在大多数动物的生活史中，变态是一个意义深远的重要转变。从幼虫到幼鱼的过渡需要一些组织的破坏，另一些组织的重新规范和新结构的产生。在腹足类软体动物的幼虫和其他门的各种幼虫中，变态是由来自环境的化学信号引起的。腹足动物变态的化学感觉诱导，其刻板的行为环境和一些形态发生运动的神经肌肉性质，以及形态变化的速度都表明幼虫神经系统的普遍控制。然而，我们对神经系统如何在整个生物体的水平上指导剧烈的形态变化的机制知之甚少。皮雷斯博士将研究腹足动物Crepidula fornicata变态的神经控制，重点关注幼虫膜破坏过程中的神经信号。这种纤毛状的游泳和觅食器官在有能力的幼虫接触到诱发变态的自然线索后，几分钟内由于几种类型的膜细胞之间的粘连丧失而迅速脱落。排列在绒膜边缘的大纤毛细胞在变态过程中最先分离，它们具有电兴奋性，并且在其他腹足类动物中被证明携带一种由突触驱动的钙介导的动作电位，导致纤毛跳动停止。在C. fornicata和其他腹足类动物中，这些纤毛在绒毛明显开始破坏之前的时刻被阻止，但没有研究调查过绒毛中的电活动与发生在变态中的细胞粘附丧失之间的机制关系。皮雷斯博士和其他人之前的研究表明，内源性多巴胺是一种神经调节剂，可以增强变态，但它对绒膜信号传导的影响尚未得到研究。也有证据表明，过氧化氢或其他活性氧在变态发育膜中产生，如果外源性应用，可以诱导膜片破坏，但目前尚不清楚活性氧是否在自然变态中介导膜片破坏的神经机制中具有必要的信号作用。皮雷斯将利用C. fornicata幼虫的大尺寸和可预测的快速变态，并利用他为分离的膜组织开发的显微外科手术方法。皮雷斯博士和他的学生将应用细胞内和细胞外电生理技术以及药理学、组织化学和高效液相色谱方法来分析神经信号如何影响变形膜中细胞粘附的快速丧失。这个项目为本科生提供了一个不同寻常的机会，让他们从事跨越生物组织几个层次的发育神经科学研究。这个项目的一个重要的进一步培训方面是，暑期工作将在华盛顿大学的星期五海港实验室进行，在那里，本科生将沉浸在一个丰富而令人振奋的科学社区中，同时他们将对未来的研究事业做出决定。

Pires0110832AbstractMetamorphosis is a profoundly important transition in the life history of most animals. The passage from a larval to juvenile form entails destruction of some tissues, respecification of others and generation of new structures. In larvae of gastropod molluscs and in a diverse range of larvae from other phyla, metamorphosis is initiated by a chemical signal from the environment. The chemosensory induction of gastropod metamorphosis, its stereotyped behavioral context and the neuromuscular nature of some morphogenic movements, and the rapidity of morphological change all suggest pervasive control by the larval nervous system. However, very little is known of the mechanisms by which the nervous system can direct dramatic morphological change at the level of the entire organism. Dr. Pires will investigate the neural control of metamorphosis in the gastropod, Crepidula fornicata, focusing on neural signaling in the destruction of the larval velum. This ciliated swimming and feeding organ is precipitously shed by loss of adhesion among and between several types of velar cells within minutes after competent larvae come in contact with the natural cue that induces metamorphosis. The large ciliated cells that line the margin of the velum are the first to detach in metamorphosis, are electrically excitable, and have been shown in other gastropods to carry a synaptically-driven calcium-mediated action potential that causes arrest of ciliary beating. These cilia are arrested in C. fornicata and other gastropods in the moments before destruction of the velum visibly begins, yet no studies have investigated the mechanistic relationship between electrical activity in the velum and the loss of cell adhesion that occurs in metamorphosis. Previous work by Dr. Pires and others has implicated endogenous dopamine as a neuromodulator that potentiates metamorphosis, but its effects on signaling in the velum are unexplored. There is also evidence that hydrogen peroxide or other reactive oxygen species are generated in the metamophosing velum and can induce velar destruction if exogenously applied, but it is not known if reactive oxygen species have a necessary signaling role in a neural mechanism that mediates velar destruction in natural metamorphosis.Dr. Pires will exploit the large size and predictably fast metamorphosis of C. fornicata larvae, and take advantage of microsurgical methods that he developed for working with isolated velar tissues. Dr. Pires and his students will apply intracellular and extracellular electrophysiological techniques as well as pharmacological, histochemical and high-performance liquid chromatographic methods to analyze how neural signals effect a rapid loss of cell adhesion in the metamorphosing velum. This project affords undergraduate research students an unusual opportunity to engage in developmental neuroscience that cuts across several levels of biological organization. An important further training dimension of this project is that summer work will take place at the University of Washington's Friday Harbor Laboratories, where undergraduates will be immersed in a rich and exhilarating scientific community at a time when they will be making decisions about future research careers.