A newly discovered feed-forward mechanism controls photoreceptor fate

新发现的前馈机制控制光感受器的命运

• 批准号: 8673174
• 负责人: James G. Patton
• 金额: $ 39.17万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-04-01 至 2017-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8673174
• 关键词: Aging; Animal Model; Aqueous Humor; Biological Models; Blindness; Boxing; Cell Count; Cell Differentiation process; Cells; Cessation of life; Chimeric Proteins; Cone; Development; Disease; Dose; Embryo; Event; Eye; Future; Gene Expression; Genes; Genetic; Genetic Transcription; Growth; Health; Image; Imaging Techniques; Knowledge; Laboratories; Life; Ligase; Macular degeneration; Modeling; Molecular; Mutation; Nuclear Hormone Receptors; Pathway interactions; Patients; Photoreceptors; Pineal gland; Post-Translational Protein Processing; Production; Proteins; Replacement Therapy; Research Personnel; Retina; Retinal; Retinal Cone; Retinal Degeneration; Retinal Diseases; Retinitis Pigmentosa; Small Ubiquitin-Related Modifier Proteins; Stem cells; Syndrome; System; Testing; Time; Transgenes; Transgenic Organisms; Translations; Transplantation; Vertebrate Photoreceptors; Vision; Zebrafish; disease-causing mutation; dosage; feeding; in vivo; inherited retinal degeneration; insight; lens; mutant; novel; photoreceptor degeneration; precursor cell; premature; programs; protein activation; public health relevance; restoration; retinal progenitor cell; retinal rods; stem cell therapy; success; time use; tool; transcription factor; zebrafish development

DESCRIPTION (provided by applicant): Retinal degeneration is a devastating affliction that leads to irreversible loss of vision, resulting from the progressive death of rod and cone photoreceptor cells in the outermost layer of the retina. One of the most promising avenues for replacing photoreceptors following degeneration is the introduction of photoreceptor precursor cells into the retina, which can differentiate into rods and cones. However, in trials of precursor transplant therapy, too many rods and not enough cones are produced. The result of these trials reveals a major hurdle for restoration of vision using stem-cell therapies, and highlights a criticl gap in our knowledge of photoreceptor formation: We do not know the mechanism that switches precursors from production of cone photoreceptors, which arise first, to production rod photoreceptors, which arise second. In order to understand how the number of cone versus rod photoreceptors is regulated, we have established a simple but powerful tool to study photoreceptor development, the zebrafish pineal organ, which shares a very close evolutionary relationship with the eyes. Just as in the retina, the zebrafish pineal contain fully developed rod and cone photoreceptors; in addition, the pineal photoreceptors are molecularly quite similar to those in the retina. A major advantage of the zebrafish pineal for studying photoreceptor development is its simplicity, which allows imaging of the live or fixed pineal organ easily in whole mount embryos without sectioning since there is no interference from the lens, aqueous humor, or overlying retinal layers. Recent studies from our laboratory indicate a novel and unexpected mechanism, called an incoherent feed-forward system, which controls the number of cone and rod cells produced by photoreceptor precursors. We propose that in early photoreceptor precursors, which give rise to cone cells, time-limited expression of the transcription factor Tbx2b expression drives the expression of cone-specific genes and also initiates expression of the cone-gene repressor Nr2e3. Nr2e3 protein continues to accumulate until it reaches a threshold concentration that shuts off cone gene expression and allows rods to form instead. In order to test the implications of our feed-forward hypothesis for photoreceptor formation, we will take advantage of the genetic tools that we and others have generated in zebrafish. Then we will leverage our knowledge to test the effects of a disease-causing mutation in Nr2e3 on feed-forward control. Our studies will illuminate the molecular control of cone versus rod production, which will provide invaluable information for laboratories developing retinal replacement therapies as well as insight into the ontogeny of inherited retinal degeneration disorders.

描述（由申请人提供）：视网膜变性是一种毁灭性的疾病，会导致不可逆的视力丧失，这是由于视网膜最外层的视杆细胞和视锥细胞感光细胞逐渐死亡所致。替换退化后的光感受器的最有希望的途径之一是将光感受器前体细胞引入视网膜，该细胞可以分化为视杆细胞和视锥细胞。然而，在先行者的试验中 移植疗法中，产生的视杆细胞过多而视锥细胞不足。这些试验的结果揭示了使用干细胞疗法恢复视力的一个主要障碍，并强调了我们对光感受器形成知识的一个关键差距：我们不知道将前体从首先产生的视锥细胞光感受器的产生转变为随后产生的杆状光感受器的产生的机制。为了了解视锥细胞和视杆细胞的数量是如何调节的，我们建立了一个简单但强大的工具来研究光感受器的发育，即斑马鱼松果体，它与眼睛具有非常密切的进化关系。就像视网膜一样，斑马鱼的松果体含有完全发育的视杆细胞 和视锥细胞感光器；此外，松果体感光细胞在分子上与视网膜中的感光细胞非常相似。斑马鱼松果体用于研究光感受器发育的一个主要优点是它的简单性，它允许在整个胚胎中轻松地对活体或固定松果体器官进行成像，而无需切片，因为没有晶状体、房水或覆盖的视网膜层的干扰。我们实验室最近的研究表明了一种新颖且意想不到的机制，称为不相干前馈系统，它控制由光感受器前体产生的视锥细胞和视杆细胞的数量。我们提出，在产生视锥细胞的早期光感受器前体中，转录因子 Tbx2b 表达的限时表达驱动视锥特异性基因的表达，并启动视锥基因抑制子 Nr2e3 的表达。 Nr2e3 蛋白继续积累，直到达到阈值浓度，该阈值浓度会关闭视锥细胞基因表达并允许视杆细胞形成。为了测试我们的前馈假设对光感受器形成的影响，我们将利用我们和其他人在斑马鱼中产生的遗传工具。然后，我们将利用我们的知识来测试 Nr2e3 中的致病突变对前馈控制的影响。我们的研究将阐明视锥细胞与视杆细胞产生的分子控制，这将为开发视网膜替代疗法的实验室提供宝贵的信息，并深入了解遗传性视网膜变性疾病的个体发育。