Molecular-genetic analysis of habituation learning

 描述（由申请人提供）：学习反映了动物不断更新其行为反应的能力，这些反应来自于从环境中获得的新信息。习惯化是一种简单的学习形式，它允许动物停止对重复的、无威胁的视觉、触觉或听觉刺激做出反应。在人类中，习惯性学习在精神分裂症和注意力缺陷障碍中被破坏。然而，尽管它的重要性，遗传 控制对习惯化至关重要的神经元回路的组装和功能的程序和分子机制还没有被很好地理解。 斑马鱼幼鱼表现出许多与神经精神疾病研究相关的复杂行为，包括前脉冲抑制和惊吓习惯化。Granato实验室开发了一种自动化、高通量测定法来测量惊吓习惯，并进行了一项小分子筛选，揭示了惊吓习惯的神经药理学底物在斑马鱼和人类之间是保守的。此外，Granato实验室已经进行了第一次正向遗传筛选，以寻找对脊椎动物惊吓习惯至关重要的基因。这个筛选已经确定了八个在习惯性学习方面有缺陷的突变体，实验室已经确定了其中三个突变体的分子病变。其中一种突变表型是由妊娠相关血浆蛋白a（papp-a）的假定无效突变引起的，这是一种脊椎动物特异性基因，以前与习惯性学习无关。尽管papp-a在哺乳动物大脑中表达，但其在神经系统发育或功能中的作用尚不清楚。在这里，我建议确定这个基因在哪里以及何时起作用来调节习惯化（目标1）。由于papp-a在胰岛素样生长因子（IGF）信号传导中起着有据可查的作用，我将确定papp-a对习惯化的调节是通过经典的IGF信号传导途径还是通过一种新的IGF信号传导独立途径（目的2）。为了确定对惊吓习惯化至关重要的其他调节因子，我将应用全基因组测序来确定在筛选中分离的另外两个习惯化突变体中突变的基因。 结合这些实验，将表征papp-a基因在调节习惯化行为中的功能，并鉴定脊椎动物环境中调节习惯化行为所需的新基因。这些研究将阐明介导惊吓习惯化的细胞的发育和功能所需的细胞和分子机制。鉴于惊吓习惯和学习过程对健康和疾病状态下神经系统功能的重要性，拟议的研究与基础科学和人类健康都具有高度相关性。

 DESCRIPTION (provided by applicant): Learning reflects the ability of animals to constantly update their behavioral responses with new information obtained from their environments. Habituation is a simple form of learning, and allows animals to cease responding to repeated and non-threatening visual, tactile or acoustic stimuli. In humans, habituation learning is disrupted in schizophrenia and attention deficit disorders. Yet despite its importance, the genetic programs and molecular mechanisms that govern the assembly and function of the neuronal circuits critical for habituation are not well understood. Larval zebrafish exhibit numerous complex behaviors relevant to the study of neuropsychiatric disorders, including prepulse inhibition and startle habituation. The Granato lab has developed an automated, high-throughput assay that measures startle habituation, and has conducted a small molecule screen that revealed that the neuro-pharmacological substrates for startle habituation are conserved between zebrafish and humans. Furthermore, the Granato lab has conducted the first forward genetic screen for genes critical for vertebrate startle habituation. This screen has identified eight mutants with deficits in habituation learning, and the lab has already identified the molecular lesions for three of these mutants. One of the mutant phenotypes is caused by a presumptive null mutation in pregnancy associated plasma protein a (papp-a), a vertebrate specific gene previously not implicated in habituation learning. Although papp-a is expressed in the mammalian brain, its role in nervous system development or function is unknown. Here, I propose to identify where and when this gene acts to regulate habituation (Aim 1). Since papp-a plays a well-documented role in insulin-like growth factor (IGF) signaling, I will determine whether papp-a's regulation of habituation is executed through the canonical IGF signaling pathway or through a novel, IGF signaling independent pathway (Aim 2). To identify additional regulators critical for startle habituation, I will apply whole genome sequencing to identify the genes mutated in two additional habituation mutants isolated in the screen. Combined, these experiments will characterize the function of the papp-a gene in regulating habituation behaviors and identify novel genes required for the regulation of habituation behaviors in a vertebrate context. These studies will illuminate the cellular and molecular mechanisms required for the development and function of cells mediating startle habituation. Given the importance of startle habituation and learning processes for nervous system function in healthy and disease states, the proposed studies are of high relevance to both basic science and human health.