Development of Visual Connections

视觉联系的发展

• 批准号: 9265185
• 负责人: Carla J Shatz
• 金额: $ 15.84万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2017-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9265185
• 关键词: Acute; Adolescent; Adult; Age; Aging; Alleles; Alzheimer' s Disease; Amblyopia; Apical; Autistic Disorder; Biochemical; Blocking Antibodies; Brain; Brain-Derived Neurotrophic Factor; CREB1 gene; Cells; Childhood; Clinical; Dendrites; Dendritic Spines; Development; Drug Targeting; Dyslexia; Effectiveness; Electrophysiology (science); Employee Strikes; Equilibrium; Etiology; Eye; FRAP1 gene; Family; Genes; Genetic; Germ Lines; Goals; Histocompatibility; Human; Image; Immune system; Immunoglobulins; In Vitro; Label; Learning; Learning Disabilities; Life; Ligands; Link; Long-Term Depression; Long-Term Potentiation; Measures; Mediating; Memory Loss; Methods; Microscopy; Mitogen-Activated Protein Kinases; Molecular; Mus; Neurodegenerative Disorders; Neuronal Plasticity; Neurons; Ocular Dominance; Pathway interactions; Phosphorylation; Physiological; Proteins; Proto-Oncogene Proteins c-akt; Recombinants; Recovery; Repression; Signal Pathway; Signal Transduction; Signal Transduction Pathway; Slice; Stroke; Synapses; Synaptic plasticity; System; T-Cell Receptor; Tamoxifen; Testing; Transgenic Mice; Transgenic Organisms; Vertebral column; Visual; Visual Cortex; Visual system structure; base; cell motility; cell type; critical developmental period; critical period; density; design; experience; fetal; hippocampal pyramidal neuron; in vivo; loss of function; member; monocular; monocular deprivation; novel therapeutics; optical imaging; postnatal; receptor; relating to nervous system; repaired; research study; two-photon; vision development; white matter

DESCRIPTION (provided by applicant): What enables a baby's brain to learn so rapidly during early developmental critical periods? What cell and molecular mechanisms cause the decline in extensive plasticity by adulthood? The goal here is to enhance synaptic plasticity by discovering and then blocking endogenous mechanisms that function to suppress plasticity and circuit change. Specifically, can manipulations of the neuronal receptor PirB (Paired Immunoglobulin-like receptor B; Lilrb3 in humans) "release the brake" on ocular dominance (OD) plasticity, a form of experience-dependent synaptic plasticity in visual cortex? In the immune system PirB is a receptor for Major Histocompatibility Class I molecules, famous ligands for T-cell receptors. This Lab made the unexpected discovery that neurons express PirB and MHCI molecules at synapses. OD plasticity is enhanced in visual cortex of mice with germline deletion of PirB, consistent with PirB acting to brake synaptic plasticity. Three specific aims are proposed: 1) Determine if acute deletion of PirB postnatally enhances OD plasticity: A conditional allele of PirB (PirB flox/flox) has been made, allowing acute temporal and cell-type disruption of PirB by crossing mice with tamoxifen-inducible Cre transgenic lines. Direct blockade of PirB with recombinant soluble truncated PirB protein or function-blocking antibodies will also be used. These experiments should reveal when and in what cell types PirB acts. 2) Link enhanced OD plasticity in PirB-/- mice to cellular mechanisms of synaptic plasticity. Long-term potentiation (LTP) and long-term depression (LTD) will be studied in vitro in visual cortex slices using physiological methods. Dendritic spine density of YFP-labeled layer 5 pyramidal neurons will be measured in PirB-/- vs WT mice reared with normal visual experience or with monocular eye closure; spine stability will be examined using two-photon microscopy. These experiments should broaden understanding of how PirB acts at synaptic and structural levels to suppress plasticity. 3) Identify PirB signal transduction pathways in mouse visual cortex: Candidate signaling pathways downstream of PirB will be identified and evaluated by comparing visually-driven signaling in WT vs germline PirB-/- mouse visual cortex during and after the critical period. Changes in expression and phosphorylation levels will be assessed in candidate pathways including MAP Kinase, AKT and mTOR signaling. Studies here will employ genetic, biochemical, electrophysiological, imaging and anatomical methods in mice to assess OD plasticity at the systems level and to understand cellular and molecular mechanisms of PirB function. Together, experiments should elucidate how PirB normally acts in neurons to suppress synaptic-plasticity signaling pathways during and beyond the critical period, as well as test feasibility of restoring OD plasticity by acute PirB blockade. They represent key steps in understanding mechanisms of developmental critical periods, as well as for designing new ways to enhance CNS function and repair by engaging the brain's inherent capacity for neural plasticity.

描述（由申请人提供）：是什么让婴儿的大脑在早期发育关键期能够如此快速地学习？哪些细胞和分子机制导致成年后广泛可塑性下降？这里的目标是通过发现并阻断抑制可塑性和电路变化的内源机制来增强突触可塑性。具体来说，神经元受体 PirB（配对免疫球蛋白样受体 B；人类中的 Lilrb3）的操作能否“释放制动”对眼优势 (OD) 可塑性（视觉皮层中一种依赖于经验的突触可塑性的形式）？在免疫系统中，PirB 是主要组织相容性 I 类分子的受体，是 T 细胞受体的著名配体。该实验室意外发现神经元在突触处表达 PirB 和 MHCI 分子。 PirB 种系缺失的小鼠视觉皮层的 OD 可塑性增强，这与 PirB 抑制突触可塑性的作用一致。提出了三个具体目标：1) 确定 PirB 的出生后急性缺失是否会增强 OD 可塑性：PirB 的条件等位基因 (PirB flox/flox) 已被制备，通过将小鼠与他莫昔芬诱导的 Cre 转基因系杂交，可以对 PirB 进行急性时间和细胞类型破坏。还将使用重组可溶性截短 PirB 蛋白或功能阻断抗体直接阻断 PirB。这些实验应该揭示 PirB 何时以及在哪些细胞类型中发挥作用。 2) 将 PirB-/- 小鼠中增强的 OD 可塑性与突触可塑性的细胞机制联系起来。将使用生理学方法在体外视觉皮层切片中研究长时程增强（LTP）和长时程抑制（LTD）。将在 PirB-/- 与以正常视觉体验或单眼闭合饲养的 WT 小鼠中测量 YFP 标记的第 5 层锥体神经元的树突棘密度；将使用双光子显微镜检查脊柱稳定性。这些实验应该可以加深对 PirB 如何在突触和结构水平上发挥作用以抑制可塑性的理解。 3) 识别小鼠视觉皮层中的 PirB 信号转导通路：通过比较关键期期间和之后 WT 与种系 PirB-/- 小鼠视觉皮层中的视觉驱动信号，将识别和评估 PirB 下游的候选信号转导通路。将在候选途径（包括 MAP 激酶、AKT 和 mTOR 信号传导）中评估表达和磷酸化水平的变化。这里的研究将采用小鼠遗传、生化、电生理学、成像和解剖学方法来评估系统水平的 OD 可塑性，并了解 PirB 功能的细胞和分子机制。总之，实验应阐明 PirB 如何在神经元中正常发挥作用，以在关键期期间和之后抑制突触可塑性信号通路，并测试通过急性 PirB 阻断恢复 OD 可塑性的可行性。它们代表了理解发育关键期机制的关键步骤，以及设计新方法通过利用大脑固有的神经可塑性能力来增强中枢神经系统功能和修复的关键步骤。