Cerebellar gene expression profiles of mouse models for Rett syndrome reveal novel MeCP2 targets
Cerebellar gene expression profiles of mouse models for Rett syndrome reveal novel MeCP2 targets
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DOI：
10.1186/1471-2350-8-36
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发表时间：
2007-06-20
影响因子：
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通讯作者：
Francke, Uta
中科院分区：
文献类型：
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作者：
Jordan, ChaRandle;Li, Hong Hua;Francke, Uta
背景：MeCP2（甲基CpG结合蛋白2）与CpG二核苷酸中的甲基化胞嘧啶以及未甲基化的DNA结合，并影响染色质浓缩。女性中的MECP2突变会导致瑞特综合征，这是一种神经系统疾病，其特征为发育停滞和倒退、有目的的手部动作和语言丧失、刻板的手部动作、脑生长减速、自主神经功能障碍和癫痫发作。大多数突变在精子发生过程中从头发生。MECP2位于Xq28，受X染色体失活影响，患病女性呈嵌合体。罕见的半合子男性患有严重的先天性脑病。
方法：为了确定因MeCP2缺乏而失调的通路，在Mecp2突变小鼠的小脑中进行了基于微阵列的全基因表达研究。我们比较了两种不同的MeCP2缺陷小鼠模型在2、4和8周龄时突变型/野生型雄性同窝小鼠的转录水平。通过实时定量RT - PCR评估转录水平的升高。染色质免疫沉淀试验用于证明体内MeCP2与候选靶基因启动子区域的结合。
结果：在突变体中表达水平改变的数百个基因中，升高的基因数量是降低的基因数量的两倍，且只有27个基因在多个时间点有差异表达。外显子3缺失的小鼠（Mecp2(tm1.1Jae)）中失调基因的数量比缺失较大的小鼠（Mecp2(tm1.1Bird)）低30%。在突变体之间，每个时间点只有少数基因重叠。实时定量RT - PCR试验验证了四个基因转录水平的升高：Irak1（白细胞介素 - 1受体相关激酶1）；Fxyd1（磷酸受纳蛋白，与钠钾ATP酶相关）；Reln（编码一种对神经元分层和突触可塑性至关重要的细胞外信号分子）；以及Gtl2/Meg3（一种母源印记的非翻译RNA，作为C/D盒小核仁RNA和微小RNA的宿主基因）。染色质免疫沉淀试验证明了体内MeCP2与Fxyd1、Reln和Gtl2启动子区域的结合。
结论：小脑的转录谱分析未能在Mecp2突变小鼠中检测到显著的全局变化。Irak1、Fxyd1、Reln和Gtl2转录水平的升高可能导致MeCP2缺陷小鼠和瑞特综合征患者的神经元功能障碍。我们的数据为这些基因所作用的调节或信号通路的未来研究提供了可检验的假设。
Background: MeCP2, methyl-CpG-binding protein 2, binds to methylated cytosines at CpG dinucleotides, as well as to unmethylated DNA, and affects chromatin condensation. MECP2 mutations in females lead to Rett syndrome, a neurological disorder characterized by developmental stagnation and regression, loss of purposeful hand movements and speech, stereotypic hand movements, deceleration of brain growth, autonomic dysfunction and seizures. Most mutations occur de novo during spermatogenesis. Located at Xq28, MECP2 is subject to X inactivation, and affected females are mosaic. Rare hemizygous males suffer from a severe congenital encephalopathy.Methods: To identify the pathways mis-regulated by MeCP2 deficiency, microarray-based global gene expression studies were carried out in cerebellum of Mecp2 mutant mice. We compared transcript levels in mutant/wildtype male sibs of two different MeCP2-deficient mouse models at 2, 4 and 8 weeks of age. Increased transcript levels were evaluated by real-time quantitative RT-PCR. Chromatin immunoprecipitation assays were used to document in vivo MeCP2 binding to promoter regions of candidate target genes.Results: Of several hundred genes with altered expression levels in the mutants, twice as many were increased than decreased, and only 27 were differentially expressed at more than one time point. The number of misregulated genes was 30% lower in mice with the exon 3 deletion (Mecp2(tm1.1Jae)) than in mice with the larger deletion (Mecp2(tm1.1Bird)). Between the mutants, few genes overlapped at each time point. Real- time quantitative RT-PCR assays validated increased transcript levels for four genes: Irak1, interleukin-1 receptor-associated kinase 1; Fxyd1, phospholemman, associated with Na, K-ATPase; Reln, encoding an extracellular signaling molecule essential for neuronal lamination and synaptic plasticity; and Gtl2/Meg3, an imprinted maternally expressed non-translated RNA that serves as a host gene for C/D box snoRNAs and microRNAs. Chromatin immunoprecipitation assays documented in vivo MeCP2 binding to promoter regions of Fxyd1, Reln, and Gtl2.Conclusion: Transcriptional profiling of cerebellum failed to detect significant global changes in Mecp2-mutant mice. Increased transcript levels of Irak1, Fxyd1, Reln, and Gtl2 may contribute to the neuronal dysfunction in MeCP2- deficient mice and individuals with Rett syndrome. Our data provide testable hypotheses for future studies of the regulatory or signaling pathways that these genes act on.