Sp4 pathway in hippocampus modulates sensorimotor gating

描述(申请人提供)：海马体异常是几种人类精神疾病的重要易感因素。感觉运动门控，通过对惊吓的脉冲前抑制来评估，在一组精神门控障碍中减少并提供了一种跨物种的内表型，包括精神分裂症、双相情感障碍、自闭症和ADHD。在初步工作中，低形态SP4突变小鼠显示出海马齿状回中的空泡化，海马区和皮质中Grk4基因表达减少，感觉运动门控和上下文记忆方面的严重缺陷，以及对新环境的探索减少。SP4突变小鼠的分子、海马体和行为异常与神经精神门控障碍的几种表型相似。具体目标1将评估SP4基因在齿状回空泡化过程中的细胞自主作用，以及与之相关的感觉运动门控和上下文记忆方面的缺陷。通过内部核糖体进入位点，将可诱导的cre-ERT2基因融合在内源性桥粒蛋白(DSP)基因的3‘非编码区，从而建立小鼠系，而不会敲除DSP的表达。他莫昔芬将被用来激活ERE，而ERE又将重新激活或消除齿状颗粒细胞中SP4的表达。将对这些救援性或条件性基因敲除小鼠的海马体结构和功能异常进行评估。特定目标2将确定海马体中SP4介导的遗传路径，这些路径有助于新的对象探索。研究将(A)在已建立的范式中进一步分析低形态SP4小鼠的缺陷新颖性探索；(B)检验恢复或去除齿状颗粒细胞中SP4的表达(目标1)是否可以挽救或导致缺陷新颖性反应。具体目标3将使用药理学和遗传学方法，研究Grk4介导的信号通路在SP4亚型小鼠感觉运动门调节中的作用。细胞培养实验将检测Grk4介导的多巴胺D1和mGluRI受体在SP4突变的海马细胞中的脱敏作用。多巴胺D1和mGluRI受体的拮抗剂将被应用于低形态SP4突变小鼠，以测试脉冲前抑制缺陷的逆转。为了评价Grk4介导的GPCR信号通路在调节感觉运动门和海马空泡化中的破坏作用，我们将建立SP4缺失与多巴胺D1或mGluRI受体基因相结合的双基因敲除小鼠。这些实验将对海马体内的遗传路径产生新的见解，这些遗传路径是与几种精神障碍相关的行为异常的基础。

DESCRIPTION (provided by applicant): Hippocampal abnormalities are important susceptibility factors for several human psychiatric disorders. Sensorimotor gating, assessed by prepulse inhibition of startle, is reduced in and provides a cross-species endophenotype for a group of psychiatric gating disorders, including schizophrenia, bipolar disorder, autism, and ADHD. In preliminary work, hypomorphic Sp4 mutant mice displayed vacuolization in the hippocampal dentate gyrus, reduced expression of the Grk4 gene in the hippocampus and cortex, robust deficits in sensorimotor gating and contextual memory, and decreased exploration of novel environments. The molecular, hippocampal, and behavioral abnormalities of the Sp4 mutant mice mimic several phenotypes for neuropsychiatric gating disorders. Specific Aim 1 will assess the cell autonomous roles of the Sp4 gene in the vacuolization of dentate gyrus, and the associated deficits in sensorimotor gating and contextual memory. A mouse line will be created with an inducible cre-ERT2 gene fused within the 3' UTR of the endogenous Desmoplakin (Dsp) gene by internal ribosome entry site without knocking-out Dsp expression. Tamoxifen will be used to activate the ere that in turn will reactivate or ablate the Sp4 expression in dentate granule cells. Hippocampal structural and functional abnormalities will be assessed in these rescue or conditional knockout mice. Specific Aim 2 will identify Sp4-mediated genetic pathways in the hippocampus that subserve novel object exploration. Studies will (a) further analyze the defective novelty exploration of the hypomorphic Sp4 mice in established paradigms; (b) examine whether the restoration or ablation of Sp4 expression in the dentate granule cells (Aim 1) can rescue or cause the defective novelty response. Specific Aim 3 will examine the role of the Grk4-mediated signaling pathway in the modulation of sensorimotor gating in Sp4 hypomorphic mice, using both pharmacological and genetic approaches. Cell culture experiments will examine Grk4-mediated desensitization of both dopamine D1 and mGluRI receptors in the Sp4 mutant hippocampal cells. Antagonists of dopamine D1 and mGluRI receptors will be administered to the hypomorphic Sp4 mutant mice to test for reversal of the prepulse inhibition deficit. To evaluate the disruption of Grk4-mediated GPCR signaling pathway in the modulation of sensorimotor gating and hippocampal vacuolization, double knockout mice combining the Sp4 deletion with either dopamine D1 or mGluRI receptor genes will be generated. These experiments will yield novel insights into genetic pathways within the hippocampus that underlie behavioral abnormalities relevant to several psychiatric disorders.