Circadian Clock Genes Are Essential for Normal Adult Neurogenesis, Differentiation, and Fate Determination.
Circadian Clock Genes Are Essential for Normal Adult Neurogenesis, Differentiation, and Fate Determination.
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DOI：
10.1371/journal.pone.0139655
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Geusz ME
中科院分区：
文献类型：
--
作者：
Malik A;Kondratov RV;Jamasbi RJ;Geusz ME
成人神经发生终生由人类大脑中的干细胞产生新的神经元和神经胶质细胞。它在海马齿状回(DG)和脑室下区(SVZ)中被最好地理解。在海马区已经发现了昼夜节律，但任何内源性昼夜节律振荡器细胞在海马神经发生中的作用及其在学习或记忆中的重要性仍不清楚。任何通过DG内固有的昼夜节律调节干细胞的研究都因大脑其他地方的昼夜节律的调制而变得复杂。为了在更孤立的情况下检验昼夜节律振荡器，从两个缺乏功能昼夜节律钟的敲除小鼠品系的DG和mPer1：：Luc小鼠的DG中制备神经球培养物，以鉴定基因表达的昼夜节律振荡。MPer1基因的昼夜节律被记录在神经球中，维持在诱导神经发生的培养液中，而不是在维持干细胞状态的培养液中。尽管球体分化的神经干细胞前体细胞是有节律性的，但任何成熟神经元的证据都非常稀少。昼夜节律信号起源于神经球内的未分化细胞。这一结论得到了mPER1蛋白免疫细胞化学的支持，mPER1蛋白定位于内部更像干细胞的神经球核心。为了测试生物钟对神经发生的影响，改变培养条件以诱导BMAL1基因敲除小鼠的神经球分化。根据GFAP和NeuN的表达，这些培养物显示出异常高的分化为胶质细胞，而不是神经元，很少观察到BetaIII微管蛋白阳性的未成熟神经元。基因敲除的神经球也显示出明显的无细胞区域，细胞死亡率总体较高。缺乏另外两个核心时钟基因的心律失常小鼠的神经球在分化过程中显示出显著的生长抑制和星形胶质细胞增殖，但它们产生了正常百分比的神经细胞。因此，神经元的命运承诺似乎是通过BMAL1的非时钟功能来控制的。这项研究为细胞自主生物钟和时钟基因如何调节成人神经干细胞提供了洞察力，并对通过操纵神经发生来治疗神经退行性疾病和受损的大脑功能具有启示意义。
Adult neurogenesis creates new neurons and glia from stem cells in the human brain throughout life. It is best understood in the dentate gyrus (DG) of the hippocampus and the subventricular zone (SVZ). Circadian rhythms have been identified in the hippocampus, but the role of any endogenous circadian oscillator cells in hippocampal neurogenesis and their importance in learning or memory remains unclear. Any study of stem cell regulation by intrinsic circadian timing within the DG is complicated by modulation from circadian clocks elsewhere in the brain. To examine circadian oscillators in greater isolation, neurosphere cultures were prepared from the DG of two knockout mouse lines that lack a functional circadian clock and from mPer1::luc mice to identify circadian oscillations in gene expression. Circadian mPer1 gene activity rhythms were recorded in neurospheres maintained in a culture medium that induces neurogenesis but not in one that maintains the stem cell state. Although the differentiating neural stem progenitor cells of spheres were rhythmic, evidence of any mature neurons was extremely sparse. The circadian timing signal originated in undifferentiated cells within the neurosphere. This conclusion was supported by immunocytochemistry for mPER1 protein that was localized to the inner, more stem cell-like neurosphere core. To test for effects of the circadian clock on neurogenesis, media conditions were altered to induce neurospheres from BMAL1 knockout mice to differentiate. These cultures displayed unusually high differentiation into glia rather than neurons according to GFAP and NeuN expression, respectively, and very few BetaIII tubulin-positive, immature neurons were observed. The knockout neurospheres also displayed areas visibly devoid of cells and had overall higher cell death. Neurospheres from arrhythmic mice lacking two other core clock genes, Cry1 and Cry2, showed significantly reduced growth and increased astrocyte proliferation during differentiation, but they generated normal percentages of neuronal cells. Neuronal fate commitment therefore appears to be controlled through a non-clock function of BMAL1. This study provides insight into how cell autonomous circadian clocks and clock genes regulate adult neural stem cells with implications for treating neurodegenerative disorders and impaired brain functions by manipulating neurogenesis.