Gene expression analysis in Fmr1KO mice identifies an immunological signature in brain tissue and mGluR5-related signaling in primary neuronal cultures.
Gene expression analysis in Fmr1KO mice identifies an immunological signature in brain tissue and mGluR5-related signaling in primary neuronal cultures.
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DOI：
10.1186/s13229-015-0061-9
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发表时间：
2015
期刊：
影响因子：
6.2
通讯作者：
Kohane IS
中科院分区：
文献类型：
--
作者：
Prilutsky D;Kho AT;Palmer NP;Bhakar AL;Smedemark-Margulies N;Kong SW;Margulies DM;Bear MF;Kohane IS
脆性X综合征(FXS)是一种神经发育障碍，其生化表现包括mGluR5依赖的通路调节失调，这是广泛使用培养神经元建模的。用标准的形态、功能和化学方法培养的神经元的体外表型已经显示出相当大的变异性。在这里，我们研究了在FXS小鼠模型的完整脑组织中原位获得的转录本，以了解它们如何反映体外状态。我们使用全基因组mRNA表达谱作为一种强大的表征工具来研究脆性X智力低下1(Fmr1)、敲除(KO)和野生型(WT)小鼠原代神经元培养以及胚胎海马区和皮质组织中的差异表达途径。为了研究发育轨迹并将小鼠模型数据与人类数据联系起来，我们使用人类发育的表达图谱绘制了KO/WT培养和大脑中差异表达的基因。我们发现，细胞培养的转录本比整个组织的转录本显示出更强的Fmr1KO特征。我们观察到在胚胎Fmr1KO皮质和海马组织中免疫信号通路的过度表达，以及在Fmr1KO皮质和海马原代培养中mGluR5下游信号通路的过度表达。在Fmr1KO小鼠培养中表达上调的基因往往在人类发育的早期达到高峰，而在胚胎皮质和海马区组织中差异表达的基因与人类发育后期表达的基因聚集在一起。脑组织的转录图谱主要集中在免疫机制上，而细胞培养的图谱显示神经元活性存在缺陷。我们推测，神经元的分离和培养导致了神经转录组向“幼年”或“去分化”状态的转变。此外，培养的神经元缺乏与神经胶质细胞的紧密偶联，这可能是完整脑内免疫表型的原因。我们的结果表明，培养的细胞可能概括了疾病的早期阶段，这一阶段也较少被随后在胚胎大脑中观察到的“免疫学”表型和体内代偿机制所掩盖。总之，这些结果表明，与整个脑组织相比，培养的原代神经元细胞的转录组更有力地证明了Fmr1KO和WT小鼠之间的差异，并可能揭示了一种分子表型，这种表型通常被体内存在的代偿机制所隐藏。此外，培养可能有助于研究人类早期大脑发育中被扰乱的途径，以及之前与自闭症有关的基因。本文的在线版本(doi：10.1186/s13229-0150061-9)包含补充材料，授权用户可以使用。
Fragile X syndrome (FXS) is a neurodevelopmental disorder whose biochemical manifestations involve dysregulation of mGluR5-dependent pathways, which are widely modeled using cultured neurons. In vitro phenotypes in cultured neurons using standard morphological, functional, and chemical approaches have demonstrated considerable variability. Here, we study transcriptomes obtained in situ in the intact brain tissues of a murine model of FXS to see how they reflect the in vitro state. We used genome-wide mRNA expression profiling as a robust characterization tool for studying differentially expressed pathways in fragile X mental retardation 1 (Fmr1) knockout (KO) and wild-type (WT) murine primary neuronal cultures and in embryonic hippocampal and cortical murine tissue. To study the developmental trajectory and to relate mouse model data to human data, we used an expression map of human development to plot murine differentially expressed genes in KO/WT cultures and brain. We found that transcriptomes from cell cultures showed a stronger signature of Fmr1KO than whole tissue transcriptomes. We observed an over-representation of immunological signaling pathways in embryonic Fmr1KO cortical and hippocampal tissues and over-represented mGluR5-downstream signaling pathways in Fmr1KO cortical and hippocampal primary cultures. Genes whose expression was up-regulated in Fmr1KO murine cultures tended to peak early in human development, whereas differentially expressed genes in embryonic cortical and hippocampal tissues clustered with genes expressed later in human development. The transcriptional profile in brain tissues primarily centered on immunological mechanisms, whereas the profiles from cell cultures showed defects in neuronal activity. We speculate that the isolation and culturing of neurons caused a shift in neurological transcriptome towards a “juvenile” or “de-differentiated” state. Moreover, cultured neurons lack the close coupling with glia that might be responsible for the immunological phenotype in the intact brain. Our results suggest that cultured cells may recapitulate an early phase of the disease, which is also less obscured with a consequent “immunological” phenotype and in vivo compensatory mechanisms observed in the embryonic brain. Together, these results suggest that the transcriptome of cultured primary neuronal cells, in comparison to whole brain tissue, more robustly demonstrated the difference between Fmr1KO and WT mice and might reveal a molecular phenotype, which is typically hidden by compensatory mechanisms present in vivo. Moreover, cultures might be useful for investigating the perturbed pathways in early human brain development and genes previously implicated in autism. The online version of this article (doi:10.1186/s13229-015-0061-9) contains supplementary material, which is available to authorized users.