The role of AC3 in neuronal activity and depression-related phenotype

 描述(由申请人提供)：尽管重度抑郁障碍(MDD)是异质性的，遗传率非常低，但一项人类全基因组关联研究表明，MDD与III型腺酰环化酶(AC3，adcy3)有关。人类血液AC3的表达水平也被认为是MDD的生物标志物，但缺乏动物研究的支持证据。我的初步数据显示，AC3常规敲除基因表现出类似抑郁的行为和许多其他相关的表型，包括睡眠模式的改变，支持AC3作为候选抑郁基因。AC3主要在中枢神经系统(CNS)的初级纤毛中表达，并被用作大脑初级纤毛的蛋白质标记物。然而，AC3也分布在其他组织中，因此AC3在抑郁症中的病理生理作用尚不清楚。为了克服传统基因敲除的局限性，并清楚地剖析AC3在大脑中的功能，我制造了一种AC3绒毛小鼠品系。这种小鼠品系已经与“EMX1-CRE”小鼠品系杂交，以特异性地消融前脑兴奋性神经元中的AC3。它还与他莫昔芬诱导的Cre系“UBC-Cre/ERT2”育成，以便在成年小鼠中暂时敲除AC3。此外，我还准备了GFP-AC3慢病毒载体，用于AC3救援实验。我将结合分子生物学、形态学、行为学、电生理学和体内成像工具来研究AC3在大脑中的功能。鉴于嗅觉纤毛中的AC3支配 对于嗅觉感觉神经元的兴奋，我将首先确定AC3是否也能类似地调节中枢神经系统神经元的电活动。我将进一步研究AC3是否调节突触密度和树突树枝形成。由于初级纤毛是神经源性Hedgehog信号所必需的，我将测试另一个假设，即AC3基因的敲除会导致成年海马神经发生的改变。此外，该项目还将进一步确定，特定干扰前脑中的AC3或在成年小鼠中暂时敲除AC3是否会导致小鼠出现类似抑郁的行为。总而言之，这项研究可以增加我们对AC3在大脑中的功能的理解，并有可能在实验上巩固AC3作为严重抑郁症的遗传风险因素。

 DESCRIPTION (provided by applicant): Although major depressive disorder (MDD) is heterogeneous and has very low heritability, a genome-wide association study in humans has implicated type III adenylyl cyclase (AC3, adcy3) in MDD. The expression level of human blood AC3 has also been considered as a MDD biomarker, but there is lack of supporting evidence from animal studies. My preliminary data demonstrate that AC3 conventional knockouts exhibit depression-like behaviors and many other related phenotypes including an altered sleeping pattern, supporting AC3 as a candidate depression gene. AC3 is predominantly expressed in primary cilia in the central nervous system (CNS) and is used as a protein marker for primary cilia throughout the brain. However, it is also distributed in other tissues so the pathophysiological role of AC3 in depression is unclear. To overcome the limitation of conventional knockouts and clearly dissect the functions of AC3 in the brain, I have generated an AC3 floxed mouse strain. This mouse strain has been crossed with the "EMX1-Cre" mouse strain to specifically ablate AC3 in excitatory neurons in the forebrain. It has also been bred wit a tamoxifen-inducible Cre line "UBC-Cre/ERT2" in order to knockdown AC3 temporally in adult mice. Moreover, I have prepared a GFP-AC3 lentiviral construct for an AC3-rescue experiment. I will combine molecular biological, morphological, behavioral, electrophysiological and in vivo imaging tools to study the functions of AC3 in the brain. Given that AC3 in olfactory cilia governs the excitation of olfactory sensory neurons, I will first determine if AC3 can similarly regulate neuronal electrical activity in CNS neurons. I will further investigate if AC3 modulates synaptic density and dendritic arborization. Since primary cilia are required for neurogenic Hedgehog signaling, I will test an alternative hypothesis that knockdown of AC3 leads to altered adult hippocampal neurogenesis. In addition, this project will further determine if specifically disrupting AC3 in the forebrain or temporally knockdown of AC3 in adult mice leads to depression-like behaviors in mice. Together, this study could increase our understanding of the functions of AC3 in the brain and has the potential to experimentally consolidate AC3 as a genetic risk factor for major depression.