Molecular identification of genes critical for vertebrate startle modulation

描述（由申请人提供）：神经系统的一个显著特征是其以依赖于环境的方式调节定型行为反应的能力。例如，突然和强烈的声音刺激会引起进化上保守的惊吓反应。虽然执行的声学惊吓反应是非常刻板，响应启动调制的上下文相关的方式。例如，重复呈现令人吃惊的刺激会抑制惊吓反应，这代表了一种简单的学习形式，称为习惯化。类似地，反应阈值以及因此惊吓敏感性也以情境依赖性方式调节，使得对于恐惧条件化动物，否则亚阈值刺激现在足以引起惊吓反应。在人类中，惊吓调节-如通过习惯化或惊吓敏感性测量的-在几种神经精神障碍中受损，包括精神分裂症、注意力缺陷障碍、亨廷顿病、强迫症（OCD）以及患有创伤后应激障碍（PTSD）的患者。尽管它的重要性，声学惊吓调制的分子机制知之甚少。斑马鱼表现出显着的行为可塑性，我们以前已经表明，幼虫表现出调制的声音惊吓反应-包括敏感性和习惯-具有里程碑式的行为和药理学特征。此外，执行斑马鱼惊吓反应的神经回路元件已经被定义，并且由于其透明性，幼虫适合于遗传和光遗传操纵。使用自动化系统，我们进行了第一个前向遗传筛选脊椎动物，以确定所需的基因声惊吓调制。我们确定了24个突变体的缺陷，在惊吓反应阈下的声音刺激，缺陷，在短期的习惯，或在这两个缺陷。这24个突变体中没有一个表现出任何总体形态缺陷或惊吓性能缺陷。通过对其中两个突变体进行全基因组测序，我们分别鉴定了接头相关蛋白复合物2 σ 1亚基（ap 2s 1）和脊椎动物特异性妊娠相关血浆蛋白-a（papp-a）的基因突变。重要的是，这两个基因以前都没有涉及调节习惯或惊吓敏感性，这表明许多剩余的（未克隆的）22突变体可能编码的基因与惊吓调制以前没有涉及这个过程中的关键作用。在这里，我们建议将全基因组测序应用于剩余的22个突变体，以遗传图谱和识别潜在的致病突变。结合我们的研究结果将增加这些突变体对整个神经科学界的科学影响，为综合研究创造一个无与伦比的平台，以破译“正常”惊吓调制的分子和神经机制，并提供与受损惊吓调制相关的神经精神疾病的见解，如精神分裂症，强迫症和创伤后应激障碍。

DESCRIPTION (provided by applicant): A remarkable feature of the nervous system is its ability to adjust stereotyped behavioral responses in a context dependent manner. For example, sudden and intense acoustic stimuli evoke the evolutionarily conserved startle response. While the execution of the acoustic startle response is extremely stereotyped, response initiation is modulated in a context-dependent manner. For example, repeated presentation of a startling stimulus suppresses the startle response, representing a simple form of learning known as habituation. Similarly, response threshold and thus startle sensitivity are also modulated in a context- dependent manner, such that for fear-conditioned animals otherwise sub-threshold stimuli are now sufficient to evoke a startle response. In humans, startle modulation -as measured by habituation or startle sensitivity- is impaired in several neuropsychiatric disorders, including schizophrenia, attention deficit disorder, Huntington's disease, obsessive-compulsive disorder (OCD) as well as in patients suffering from post-traumatic stress disorders (PTSD). Despite its importance, the molecular mechanisms underlying acoustic startle modulation are poorly understood. Zebrafish show a remarkable behavioral plasticity, and we have previously shown that larvae exhibit modulation of the acoustic startle response- including sensitivity and habituation- with landmark behavioral and pharmacological characteristics. Moreover, the neural circuit elements executing the zebrafish startle response have been defined, and due to its transparency larvae are amenable to genetic and opto-genetic manipulations. Using an automated system, we conducted the first forward genetic screen in vertebrates to identify genes required for acoustic startle modulation. We identified 24 mutants with defects in startle responsiveness to sub-threshold acoustic stimuli, defects in short-term habituation, or defects in both. None of these 24 mutants exhibit any gross morphological defects or defects in startle performance. By applying whole genome sequencing to two of these mutants, we identified gene mutations in the adaptor-related protein complex 2 sigma 1 subunit (ap2s1), and in the vertebrate specific pregnancy associated plasma protein-a (papp-a), respectively. Importantly, neither of these genes has previously been implicated in regulating habituation or startle sensitivity, suggesting that many of the remaining (un-cloned) 22 mutants may encode genes with critical roles in startle modulation previously not implicated in this process. Here, we propose to apply whole genome sequencing to the remaining 22 mutants to genetically map and identify the underlying causative mutations. Combined our results will increase the scientific impact of these mutants for the entire neuroscience community by creating an unparalleled platform for integrative studies to decipher the molecular and neural mechanisms underlying 'normal' startle modulation, and provide insights into neuropsychiatric disorders associated with impaired startle modulation, such as schizophrenia, OCD and PTSD.