Diversity in the integration of granule neurons into the postnatal olfactory bulb

描述（由申请人提供）：人脑的修复能力有限，因此，神经系统的疾病或损伤通常是不可逆的。在成年哺乳动物大脑的嗅球和海马体中添加新的神经元表明，细胞替代可能是一种有前途的脑修复策略。然而，开发成功的基于细胞替代的大脑修复策略需要了解新生成的神经元如何整合到成人大脑中预先存在的功能神经回路中。先前的观察表明，新生动物的嗅球中新神经元的整合比成年动物更有效。该提案的目标是了解与成人出生的神经元相比，可能调节新生儿大脑中产生的新神经元融入嗅球的能力增加的机制，其长期目标是将这种理解应用于改善大脑修复策略。一个重要的线索来自于我们最近的发现，即新生啮齿动物嗅球中添加的新神经元整合到嗅球回路中，其连接模式与成年动物不同。这种差异提供了一个理想的实验机会，可以揭示调节新神经元如何整合到功能性大脑回路中的机制。在本建议中，我们将集中努力实现三个目标。首先，我们将调查在成人与新生儿嗅球中产生的中间神经元的连接的差异，通过用逆转录病毒标记神经元祖细胞来分析它们的形态，并将使用遗传标记来揭示它们的突触输入。第二，我们将通过分析移植到等时或异时宿主中的神经元祖细胞衍生的颗粒神经元的形态，来分析细胞自主或靶依赖机制在建立出生后嗅球中新生神经元的不同连接模式中的贡献。第三，我们将描述如何遗传操作的活动影响新生儿或成人的灯泡中出生的新神经元的整合，通过提供到神经祖细胞三种不同的结构，以改变内在的兴奋性和新生成的灯泡神经元的突触特性。该提案将研究不同类别的神经元如何生存并与成年和新生动物大脑中的其他神经元连接。从我们描述的实验中获得的见解将指导未来的努力，将神经元的替代作为人类大脑修复的策略。

DESCRIPTION (provided by applicant): The human brain has a limited ability for repair, and thus, diseases or injuries to the nervous system are usually irreversible. The addition of new neurons into the olfactory bulb and hippocampus of the adult mammalian brain suggests that cell replacement may be a promising strategy for brain repair. However, developing successful strategies for cell-replacement based brain repair requires an understanding of how newly generated neurons integrate into pre-existing, functioning neural circuits in the adult brain. Previous observations suggest that the incorporation of new neurons into the olfactory bulb of newborn animals is more efficient than in adult animals. The goal of this proposal is to understand the mechanisms that may regulate the increased ability of new neurons generated in the newborn brain to integrate into the olfactory bulb, compared to adult-born neurons, with the long-term objective of applying this understanding towards improving strategies for brain repair. An important clue comes from our recent discovery that new neurons added to the olfactory bulb in newborn rodents integrate into the bulb circuit with a pattern of connectivity distinct from that of the adult animal. This difference offers an ideal experimental opportunity with which to uncover the mechanisms that regulate how new neurons integrate into functioning brain circuits. In this proposal we will concentrate our efforts on three aims. First, we will investigate the differences in the connectivity of interneurons generated in the adult versus the newborn olfactory bulb by labeling neuronal progenitors with retroviruses to analyze their morphology, and will use a genetic marker to reveal their synaptic input. Second, we will assay the contribution of cell-autonomous or target-dependent mechanisms in the establishment of the different patterns of connectivity of new neurons born in postnatal olfactory bulb by analyzing the morphology of granule neurons derived from neuronal progenitors after transplantation into isochronic or heterochronic hosts. Third, we will characterize how genetic manipulations of activity affect the integration of new neurons born in the bulb of newborns or adults by delivering into neural progenitors three different constructs to alter the intrinsic excitability and the synaptic properties of newly generated bulb neurons. This proposal will investigate how different classes of neurons survive and connect to other neurons in the brain of adult and newborn animals. The insights gained from the experiments that we describe will guide future efforts towards harnessing replacement of neurons as a strategy for brain repair in humans.