Sp4 Pathway in the Modulation of Sensorimotor Gating and Memory

描述(申请人提供)：基于基因操作的动物模型可以极大地帮助我们理解大脑疾病。SP4转录因子表达降低的突变小鼠表现出感觉运动门控和上下文学习方面的缺陷，这些缺陷类似于精神分裂症的假定内表型。SP4基因与精神分裂症和双相情感障碍显著相关。在小鼠的研究中，SP4基因的表达减少损害了海马CA1区的长时程增强(LTP)，损害了空间学习，并显著降低了NMDAR1的表达，NMDAR1是NMDA谷氨酸受体的核心亚单位。NMDA功能受损在精神分裂症的病理生理学中起着核心作用。这一新的SP4-NMDAR1通路的发现为与人类精神疾病相关的跨物种研究提供了基础。这一新的应用研究了SP4如何调节NMDAR1蛋白的表达，以调节涉及感觉运动、门控和认知功能的神经通路。核心假设是SP4转录后调节NMDAR1的表达，在特定脑区恢复SP4-NMDAR1的表达将逆转SP4基因缺陷小鼠的感觉运动门控和认知缺陷。四个特定的目标将检验这些假说：目的1：阐明野生型和SP4亚型小鼠NMDAR1蛋白差异表达的分子机制。NMDAR1mRNA的定位将通过原位杂交进行检测。NMDAR1蛋白的差异翻译和周转将使用TimeSTAMP2.2-Venus标签进行检测。目的：通过恢复兴奋性神经元和抑制性神经元SP4-NMDAR1的表达，逆转感觉运动门缺陷。SP4-NMDAR1在新皮质和海马区的兴奋性和抑制性神经元中的表达将恢复，以逆转SP4缺陷性小鼠的脉冲前抑制门控缺陷。分子和药理学研究将进一步确定有条件获救的小鼠的特征。目的3：确定SP4基因缺陷小鼠是否存在额叶皮质调节的认知缺陷，以及恢复额叶皮质SP4-NR1的表达是否能逆转这些缺陷。注意集转移任务和气味广度任务都将被用来检验SP4亚型和条件性获救小鼠的认知功能。目的：检测恢复海马CA1区SP4的表达是否足以逆转SP4亚型的LTP和空间学习障碍。通过将CamK2a-Cre与SP4亚型小鼠杂交，可恢复CA1中SP4-NMDAR1的表达。空间和背景记忆的形成和巩固将在携带CamK2a-CRE的SP4亚型小鼠中进行研究。这些研究将有助于阐明感觉运动门控和学习调节的分子机制，并有助于临床干预措施的发展，以防止SP4-NMDAR1途径在人类精神疾病中下调。 公共卫生相关性：SP4基因最近被认为与精神分裂症和双相情感障碍有关，它编码脑细胞中的一种重要转录因子，调节参与精神障碍认知障碍的谷氨酸能受体的功能。本项目旨在利用动物模型阐明与精神分裂症特定认知异常相关的分子机制，以帮助临床干预措施的发展，以防止人类精神疾病中SP4-谷氨酸途径的失调。

DESCRIPTION (provided by applicant): Animal models based on genetic manipulations can contribute enormously to our understanding of diseases of the brain. Mutant mice with reduced expression of the Sp4 transcription factor display deficits in sensorimotor gating and contextual learning that resemble putative endophenotypes for schizophrenia. The Sp4 gene is significantly associated with schizophrenia and bipolar disorder. In mouse studies, reduced expression of the Sp4 gene impaired long-term potentiation (LTP) in hippocampal CA1, impaired spatial learning, and markedly decreased the expression of NMDAR1, the core subunit for NMDA glutamate receptors. Impaired NMDA function plays a central role in the pathophysiology of schizophrenia. This identification of a novel Sp4-NMDAR1 pathway provides a basis for cross-species studies related to human psychiatric disorders. This renewal application investigates how Sp4 regulates expression of NMDAR1 proteins to modulate neural pathways involved in sensorimotor gating and cognitive functions. The central hypotheses are that Sp4 post-transcriptionally regulates the expression of NMDAR1 and that restoration of Sp4-NMDAR1 expression in specific brain regions will reverse both sensorimotor gating and cognitive deficits in Sp4 hypomorphic mice. Four Specific Aims will test these hypotheses: Aim 1: To elucidate molecular mechanisms for differential expression of NMDAR1 proteins between wildtype and Sp4 hypomorphic mice. The localization of NMDAR1 mRNA will be examined by in situ hybridization. The differential translation and turnover of NMDAR1 proteins will be examined using TimeSTAMP2.2-Venus tag. Aim 2: To reverse deficient sensorimotor gating by restoring Sp4-NMDAR1 expression in excitatory and inhibitory neurons respectively. The expression of Sp4-NMDAR1 will be restored in excitatory and inhibitory neurons of both neocortex and hippocampus, to reverse prepulse inhibition gating deficits in Sp4 hypomorphic mice. Molecular and pharmacological studies will further characterize the conditional rescued mice. Aim 3: To determine whether Sp4 hypomorphic mice exhibit cognitive deficits modulated by the frontal cortex, and whether restoration of Sp4-NR1 expression in frontal cortex will reverse these deficits. Both the Attentional-Set-Shifting Task and the Odor Span Task will be used to examine cognitive functions in Sp4 hypomorphic and conditional rescued mice. Aim 4: To test whether restoration of Sp4 expression in hippocampal CA1 is sufficient to reverse the LTP and spatial learning deficits in Sp4 hypomorphs. Sp4- NMDAR1 expression will be restored in CA1 by crossing CamK2a-Cre and Sp4 hypomorphic mice. The formation and consolidation of spatial and contextual memories will be examined in the Sp4 hypomorphic mice harboring CamK2a-Cre. The proposed studies will help elucidate molecular mechanisms underlying the modulation of sensorimotor gating and learning, and aid the development of clinical interventions to prevent the down-regulation of Sp4-NMDAR1 pathway in human psychiatric disorders. PUBLIC HEALTH RELEVANCE: The Sp4 gene, which has recently been associated with both schizophrenia and bipolar disorder, codes for an important transcription factor in brain cells that regulates the function of glutamatergic receptors involved in the cognitive impairments in psychiatric disorders. This project seeks to use animal models to elucidate molecular mechanisms related to specific cognitive abnormalities in schizophrenia, in order to aid the development of clinical interventions to prevent the dysregulation of the Sp4-glutamate pathway in human psychiatric disorders.