Sp4 pathway in hippocampus modulates sensorimotor gating

描述（由申请方提供）：海马异常是几种人类精神疾病的重要易感因素。通过惊吓的前脉冲抑制评估的感觉运动门控在一组精神门控障碍中减少，并为一组精神门控障碍提供了跨物种的内在表型，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突变小鼠显示海马齿状回空泡化，海马和皮质中Grk4基因表达减少，感觉运动门控和背景记忆的严重缺陷，以及对新环境的探索减少。Sp4突变小鼠的分子、海马和行为异常模拟了神经精神门控障碍的几种表型。具体目标1将评估Sp4基因在齿状回空泡化中的细胞自主作用，以及感觉运动门控和背景记忆中的相关缺陷。将产生具有通过内部核糖体进入位点融合在内源性桥粒斑蛋白（Dsp）基因的3'UTR内的诱导型cre-ERT2基因而不敲除Dsp表达的小鼠系。他莫昔芬将用于激活ere，这反过来将重新激活或消除齿状颗粒细胞中的Sp4表达。将在这些挽救或条件性敲除小鼠中评估海马结构和功能异常。具体目标2将确定Sp4介导的遗传通路在海马体中，有利于新的对象探索。研究将（a）进一步分析在已建立的范例中的亚纯型Sp4小鼠的有缺陷的新颖性探索;（B）检查齿状颗粒细胞中Sp4表达的恢复或消除（Aim 1）是否可以挽救或引起有缺陷的新颖性反应。具体目标3将研究Grk 4介导的信号通路在Sp4亚纯型小鼠感觉运动门控调制中的作用，使用药理学和遗传学方法。细胞培养实验将检测Sp4突变海马细胞中Grk4介导的多巴胺D1和mGluRI受体脱敏。将多巴胺D1和mGluRI受体拮抗剂给予低形态Sp4突变小鼠，以测试前脉冲抑制缺陷的逆转。为了评估Grk4介导的GPCR信号传导途径在感觉运动门控和海马空泡化的调节中的破坏，将产生将Sp4缺失与多巴胺D1或mGluRI受体基因组合的双敲除小鼠。这些实验将产生新的见解海马体内的遗传途径，行为异常相关的几种精神疾病的基础。

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.