Molecular-genetic analysis of habituation learning

 描述(申请人提供)：学习反映了动物不断地用从环境中获得的新信息来更新它们的行为反应的能力。习惯化是一种简单的学习形式，允许动物停止对重复的、非威胁性的视觉、触觉或声音刺激的反应。在人类中，习惯性学习在精神分裂症和注意力缺陷障碍中受到干扰。然而，尽管它很重要，但基因 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。斑马鱼幼体表现出许多与神经精神障碍研究相关的复杂行为，包括脉冲前抑制和惊吓习惯化。格拉纳托实验室已经开发出一种自动化的高通量测试，可以测量惊吓习服，并进行了小分子筛查，揭示了惊吓习服的神经药理底物在斑马鱼和人类之间是保守的。此外，格拉纳托实验室还对脊椎动物惊吓习惯化的关键基因进行了第一次正向基因筛查。这项筛查已经确定了八个在习惯性学习方面存在缺陷的突变体，实验室已经确定了其中三个突变体的分子损伤。其中一个突变表型是由妊娠相关血浆蛋白a(PAPP-a)的假定零突变引起的，PAPP-a是一种脊椎动物特有的基因，以前与习惯性学习无关。虽然PAPP-a在哺乳动物的大脑中表达，但它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何时何地起调节习惯性的作用(目标1)。由于PAPP-a在胰岛素样生长因子(IGF)信号转导中的作用已得到充分证实，我将确定PAPP-a对习惯性的调节是通过典型的IGF信号通路还是通过一种新的IGF信号非依赖通路(AIM 2)执行的。为了确定对惊吓习服至关重要的其他调节因子，我将应用全基因组测序来鉴定在屏幕上分离的另外两个习服突变体中突变的基因。结合这些实验，这些实验将表征PAPP-a基因在调节习服行为中的功能，并识别脊椎动物环境中调节习服行为所需的新基因。这些研究将阐明细胞发育和功能所需的细胞和分子机制，这些细胞和功能调节惊吓习惯化。鉴于惊吓习惯化和学习过程在健康和疾病状态下对神经系统功能的重要性，拟议的研究对基础科学和人类健康都具有很高的相关性。

 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.