Morphogenetic Role of Serotonin in Very Early Embryogenesis

血清素在早期胚胎发生中的形态发生作用

• 批准号: 0234388
• 负责人: Michael Levin
• 金额: $ 35.99万
• 依托单位: The Forsyth Institute
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-02-15 至 2006-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0234388&HistoricalAwards=false
• 关键词: Morphogenetic; Role; Serotonin; Very; Early

0234388LevinUnderstanding developmental pattern formation is fundamental to cell and evolutionary biology; it will be a vital part of biomedicine addressing birth defects, cancer, & organ/tissue regeneration by achieving fine-scale control over the structure/function of living tissues. Research in the post-genomic age requires a synthesis of genetics and molecular biology with functional physiology in vivo. Through interdisciplinary molecular and computer modeling techniques, the Levin lab seeks a detailed understanding of cellular signals that control large-scale pattern formation by modulation of gene activity and the biophysics of membrane flux. The vertebrate body-plan possesses bilateral symmetry; however, embryos also exhibit a striking left-right asymmetry (LRA) of the viscera and brain which is highly conserved across species. Why does asymmetry exist at all? What are the implications of asymmetry for the normal physiology of the heart, gut, and brain? Why are all normal individuals not only asymmetric, but asymmetric to the same direction? When, in evolution, did handed asymmetry appear? Is it connected to chirality in plants and mollusc shells? At what developmental stages is asymmetry initiated in vertebrate embryos? What are the implications of brain asymmetry for human cognition? And, how can the left-right axis be consistently oriented with respect to the other two axes in the absence of any macroscopic feature of the world which distinguishes left from right? Are quantum parity violations relevant to mesoscopic biological shape? These issues await a detailed understanding, at the molecular, genetic, and biochemical levels, of biased asymmetry in embryos since early LR steps are poorly understood. In pursuing the mechanisms of LRA, the involvement of a novel and important aspect was discovered: serotonin (5HT). 5HT is a key neurotransmitter in the central nervous system that regulates psychodynamic function and is directly implicated in both normal cognition and syndromes such as memory impairment, sleep disorders, schizophrenia, dementia, aggression, depression, etc. Thus serotonin is, potentially, a biochemical correlate of conscious states which can be used to probe the physical basis of cognition. Preliminary studies in our lab utilized the frog embryo (Xenopus) to show that (1) some members of the 5HT pathway are present in the cleavage-stage embryo (i.e., long prior to the formation of neurons) in dynamic patterns some of which display a consistent LRA, 2) 5HT signaling is functionally implicated in early steps of LRA by pharmacological experiments, and 3) the L and R sides of the embryo show differential responses to intracellular serotonin. Thus, the 5HT pathway is a promising and completely novel entrypoint into early steps of LR patterning. The proposed research will seek to understand extremely basic properties of serotonergic signaling in early embryos by capitalizing on the many advantages of Xenopus embryos over rodent and human systems for these studies, and collaborations in the neurobiology community. The aims are: (1) characterize at the embryonic and subcellular level, the localization of all LR-relevant 5HT pathway members at each stage of early development, (2) determine precisely which embryonic stages in LR patterning utilize 5HT signaling, (3) characterize a novel cytoplasmic site of functional 5HT receptors, and (4) test two specific molecular models of the role of 5HT signaling with known early steps in LR patterning. Intellectual merit and broader impacts: A direct benefit will be the characterization of a novel mechanism in embryonic left-right asymmetry, in the context of known steps in LR patterning. Importantly, since this work identifies a marker of LR asymmetry within 2 hours of fertilization, it shows that embryos know left from right far earlier than heretofore suspected in the field, as well as providing reagents which set up a direct attack on the elusive "step 1". Perhaps the most interesting are the numerous long-term, wider impacts of this interdisciplinary work. Techniques will be developed and introduced for functional developmental studies of small molecule flux in vivo. These novel embryological techniques and approaches will be taught directly to graduate students and post-docs in our lab, as well as be published and presented at scientific meetings to help disseminate valuable ideas to the scientific community which can form the basis of new future work in many labs. Particularly exciting is the fact that an early role for this neurotransmitter may suggest that serotonergic synapses are an evolutionary co-opting of far more primitive cell:cell signaling events, which will have interesting implications for evolutionary developmental biology as well as neurobiology. This provides a ready context within which to train future scientists in interdisciplinary approaches to biological problems. These studies will thus initiate an understanding of a new role for a signaling molecule well-known for its physiological relevance in adult tissue. This information will benefit society by shedding light on very basic problems of neuroscience, embryology, evolution, and the safety of pharmaceutically popular 5HT- modulating drugs during pregnancy.

0234388莱文了解发育模式的形成是细胞和进化生物学的基础;它将是生物医学解决出生缺陷，癌症，器官/组织再生的重要组成部分，通过实现对活组织结构/功能的精细控制。后基因组时代的研究需要将遗传学、分子生物学与体内功能生理学相结合。通过跨学科的分子和计算机建模技术，莱文实验室寻求对细胞信号的详细了解，这些信号通过调节基因活性和膜通量的生物物理学来控制大规模模式的形成。脊椎动物的身体平面具有双侧对称性;然而，胚胎也表现出惊人的内脏和大脑的左右不对称性（LRA），这在物种之间是高度保守的。为什么不对称会存在呢？不对称性对心脏、肠道和大脑的正常生理有什么影响？为什么所有正常的个体不仅不对称，而且向同一方向不对称？在进化过程中，手的不对称是什么时候出现的？它与植物和软体动物外壳中的手性有关吗？脊椎动物胚胎的不对称性在什么发育阶段开始？大脑的不对称性对人类认知有什么影响？而且，在世界没有任何宏观特征区分左和右的情况下，左-右轴如何相对于其他两个轴一致地定向？量子宇称违反与介观生物形状有关吗？这些问题有待详细了解，在分子，遗传和生化水平上，在胚胎中的偏见不对称，因为早期LR步骤知之甚少。在追求LRA的机制中，发现了一个新的重要方面的参与：5-羟色胺（5 HT）。5-羟色胺是中枢神经系统中调节精神动力学功能的关键神经递质，并直接涉及正常认知和综合征，如记忆障碍、睡眠障碍、精神分裂症、痴呆、攻击性、抑郁症等。因此，5-羟色胺可能是意识状态的生物化学相关物，可用于探索认知的物理基础。我们实验室的初步研究利用青蛙胚胎（非洲爪蟾）表明：（1）5 HT途径的一些成员存在于卵裂期胚胎中（即，早在神经元形成之前），其中一些显示出一致的LRA，2）通过药理学实验，5 HT信号传导在功能上涉及LRA的早期步骤，和3）胚胎的L和R侧显示出对细胞内5-羟色胺的不同反应。因此，5 HT途径是进入LR模式化早期步骤的一个有前途的、全新的切入点。拟议的研究将寻求通过利用非洲爪蟾胚胎相对于啮齿动物和人类系统的许多优势，以及神经生物学社区的合作，来了解早期胚胎中β-胡萝卜素能信号传导的基本特性。其目标是：（1）在胚胎和亚细胞水平上表征所有LR相关的5 HT途径成员在早期发育的每个阶段的定位，（2）精确确定LR模式化中的哪些胚胎阶段利用5 HT信号传导，（3）表征功能性5 HT受体的新细胞质位点，和（4）测试5 HT信号传导作用的两种特定分子模型，其具有LR模式化中已知的早期步骤。智力价值和更广泛的影响：一个直接的好处将是一个新的机制在胚胎左右不对称的特点，在LR模式的已知步骤的背景下。重要的是，由于这项工作在受精后2小时内确定了LR不对称性的标记，因此它表明胚胎从左到右的认识比迄今为止在该领域怀疑的要早得多，并且提供了直接攻击难以捉摸的“第一步”的试剂。也许最有趣的是这一跨学科工作的许多长期，更广泛的影响。技术将被开发和介绍用于小分子通量在体内的功能发育研究。这些新的胚胎学技术和方法将直接教授给我们实验室的研究生和博士后，并在科学会议上发表和展示，以帮助向科学界传播有价值的想法，这些想法可以成为许多实验室未来新工作的基础。特别令人兴奋的是，这种神经递质的早期作用可能表明，多巴胺能突触是更原始的细胞的进化选择：细胞信号事件，这将对进化发育生物学以及神经生物学产生有趣的影响。这提供了一个现成的背景下，培养未来的科学家在跨学科的方法来解决生物学问题。因此，这些研究将开始了解一个新的作用，众所周知的信号分子在成人组织中的生理相关性。这些信息将有利于社会，揭示神经科学，胚胎学，进化的基本问题，以及在怀孕期间流行的5-HT调节药物的安全性。