Role of Small RNAs in Depression Disorder

描述（由申请人提供）：小的非编码RNA，包括microRNA（miRNA）、小干扰RNA（siRNA）、重复相关小干扰RNA和piwi相关RNA，长度为21至30个核苷酸，可以形成多种细胞通路。miRNA是转录后基因表达的序列特异性调节因子，并且被认为调节数千种靶mRNA的表达，其中每种mRNA由多个miRNA靶向。尽管据估计，miRNAs可以调节多达三分之一的人类基因，但高通量测序数据表明，基因组中只有一部分小RNA被鉴定出来，其余小RNA的鉴定对于理解小RNA介导的基因调控至关重要。因此，研究小RNA在抑郁症中的作用可能是一个富有成果的研究领域，尽管目前研究不足。甲基化CpG结合蛋白1（Methyl-CpG binding protein 1，MBD 1）是表观遗传学中的一个重要分子，对基因表达调控、染色质结构建立和基因组稳定性的维持起重要作用。我们发现Mbd 1-/-小鼠表现出成年神经发生减少，学习障碍，脑5-羟色胺活性增加，焦虑和抑郁增加，以及下丘脑-垂体-肾上腺（HPA）轴缺陷。鉴于成人神经发生、5-羟色胺和HPA轴在抑郁症中的重要作用，MBD 1可能在抑郁症的发病机制中发挥重要作用。利用我们建立的小RNA分析技术，包括miRNA阵列，miRNA的定量RT-PCR和小RNA文库的高通量测序，我们发现MBD 1的缺失改变了成体神经干/祖细胞（aNSCs）和内侧额叶皮层（MFC）中特定miRNA的表达。此外，我们已经鉴定了几种已知的对aNSC中的增殖和分化至关重要的miRNA以及野生型aNSC中超过2000种先前未鉴定的小RNA。表观遗传调节和小RNA通路之间的功能串扰已经在其他物种中得到了明确的证明，我们的初步数据促使我们研究这种串扰是否是哺乳动物大脑复杂功能和相关疾病的关键调控机制。这两个相关的-R 01应用将检验由DNA甲基化介导的表观遗传机制调节的小RNA表达在抑郁症的病因学中起关键作用的假设。我们提出了一个多学科的方法，将应用我们的综合专业知识，首先确定在aNSCs中对成人神经发生至关重要的小RNA及其mRNA靶点（目标1）;然后测试MBD 1调节小RNA表达的假设，该小RNA调节5-羟色胺和HPA轴的关键因子的表达（目标2）;并最终确定小RNA介导的基因调控是否参与抗抑郁药的作用（目的3）。这项工作的成功将促进我们对小RNA在抑郁症病因学中作用的理解，并为进一步的研究和治疗开发提供新的靶点。

DESCRIPTION (provided by applicant): Small noncoding RNAs, including microRNAs (miRNAs), small interfering RNAs (siRNAs), repeat-associated small interfering RNAs and piwi-associated RNAs, 21 to 30 nucleotides in length, could shape diverse cellular pathways. MiRNAs are sequence-specific regulators of post-transcriptional gene expression, and are believed to regulate the expression of thousands of target mRNAs, with each mRNA targeted by multiple miRNAs. Although it has been estimated that miRNAs could regulate as many as one-third of human genes, high-throughput sequencing data indicates that only a portion of small RNAs in the genome have been identified, and the identification of the remaining small RNAs is critical for understanding the small-RNA- mediated gene regulation. Therefore investigating the role of small RNA in depression is likely to be a fruitful, albeit currently understudied, area of research. Methyl-CpG binding protein 1 (MBD1) is a central player of epigenetic mechanism that is critical for gene expression regulation, chromatin structure establishment, and genomic stability maintenance. We have found that Mbd1-/- mice exhibit reduced adult neurogenesis, impaired learning, increased brain serotonin activity, increased anxiety and depression, and deficits in hypothalamic-pituitary-adrenal (HPA) axis. Given the important roles of adult neurogenesis, serotonin, and HPA axis in depression, MBD1 could play important roles in the pathogenesis of depression. Using our established technologies for small RNA analyses, including miRNA array, quantitative RT-PCR of miRNAs and high-throughput sequencing of small RNA libraries, we have found that the loss of MBD1 alters the expression of specific miRNAs in both adult neural stem/progenitor cells (aNSCs) and medial frontal cortex (MFC). In addition, we have identified several known miRNAs critical for the proliferation and differentiation in aNSCs as well as more than two thousand previously unidentified small RNAs in wildtype aNSCs. Functional crosstalk between epigenetic modulation and small RNA pathway has been clearly demonstrated in other species, and our preliminary data prompts us to investigate whether such crosstalk is the key regulatory mechanism for complex functions and related disorders in mammalian brains. These two linked- R01 applications will test the hypothesis that the expression of small RNAs modulated by DNA methylation- mediated epigenetic mechanism plays critical roles in the etiology of depression disorder. We propose a multidisciplinary approach that will apply our combined expertise to first identify the small RNAs and their mRNA targets in aNSCs that are critical for adult neurogenesis (Aim 1); then test the hypothesis that MBD1 regulates the expression of small RNAs that modulate the expression of the key factors of serotonin and HPA axis (Aim 2); and finally determine whether small RNA-mediated gene regulation is involved in the effect of antidepressants (Aim 3). The success of the proposed work should advance our understanding of the role of small RNAs in the etiology of depression, and provide new targets for further research and therapeutic development.