The gene network underlying neural stem cell identity

描述（由申请人提供）：在发育中的果蝇和脊椎动物的大脑中，神经干细胞增殖，产生排列在柱状上皮中的干细胞群。在某个时间点，分化波穿过上皮，由此细胞离开上皮片并不对称地分裂成自我更新细胞和将产生神经元的更分化的神经元前体。如果没有在适当的时间触发从增殖性对称分裂到不对称分裂的转变，就不能获得正确的神经元数量和阵列。因此，有必要了解控制增殖与分化状态的潜在分子机制。在这里，我们专注于调节果蝇幼虫大脑中神经干细胞维持的基因网络。尽管已知涉及几种信号传导途径，其中之一Notch已知在哺乳动物中是保守的，但对于维持干细胞身份的调控基因网络以及这种网络在分化时如何变化并没有全局观点。 我们最近发现转录因子Zelda是神经干细胞维持和抑制分化所必需的。我们先前已经确定塞尔达作为“合子基因组激活剂”，因为它的结合先于并预测了胚盘胚胎中几乎所有的转录活性。它组织子网络并建立许多前馈回路。Zelda还与模式化转录因子一起工作，以建立其下游靶标的稳健和精确表达，从而在早期基因网络中发挥全面作用。Zelda就像一个先锋因子，早期结合靶增强子，并促进其他因子的结合 介导阶段和组织特异性激活。在这里，我们假设塞尔达在神经干细胞基因网络中起着类似的作用。除了基因检测来确定塞尔达如何与已知的信号通路相互作用，我们建议使用全基因组方法来识别神经干细胞中的所有塞尔达靶基因。这种基于发现的方法将产生一组全面的基因，用于建立全球基因网络。这项初步研究是在R03机制的范围内，因为它将为未来的研究提供基础，以进一步描绘网络中的功能连接，首先在果蝇模型系统中，然后在哺乳动物中，因为重要的相互作用可能是保守的。该提案中概述的研究有可能显着推进我们对神经干细胞分化的理解，在发育神经生物学领域具有很高的影响。

DESCRIPTION (provided by applicant): In the developing brain of flies and vertebrates alike, neural stem cells proliferate giving rise to a stem cell population arranged in a columnar epithelium. At some point in time, a wave of differentiation moves across the epithelium, whereby cells leave the epithelial sheet and split asymmetrically into a self-renewing cell and a more differentiated neuronal precursor that will produce neurons. If the transition from proliferative symmetric division to asymmetric division is not triggered at the proper time, the correct number and array of neurons is not achieved. It is therefore essential to understand the underlying molecular mechanisms controlling the proliferative versus differentiated states. Here we focus on the gene network that regulates neural stem cell maintenance in the Drosophila larval brain. Although several signaling pathways are known to be involved, one of which, Notch, is known to be conserved with mammals, there is no global view of the regulatory gene network that maintains stem cell identity, and how this changes upon differentiation. We recently found that the transcription factor Zelda is required for neural stem cell maintenance and inhibits differentiation. We had previously identified Zelda as the "zygotic-genome activator" as its binding precedes and predicts nearly all transcriptional activity in the blastoderm embryo. It organizes sub-networks and establishes many feed forward loops. Zelda also works together with the patterning transcription factors to establish robust and precise expression of their downstream targets, thus playing a comprehensive role in the early gene network. Zelda acts like a pioneer factor, binding target enhancers early and facilitating the binding of other factors that mediate stage and tissue specific activation. Here we hypothesize that Zelda plays a similar role in the neural stem cell gene network. In addition to genetic assays to determine how Zelda interacts with the known signaling pathways, we propose to use genome-wide approaches to identify all Zelda target genes in neural stem cells. This discovery-based approach will yield a comprehensive set of genes with which to build a global gene network. This pilot study is within the scope of the R03 mechanism as it will provide the basis for future studies to further delineate functional connections in the network, first in the Drosophila model system, and then in mammals, since important interactions are likely conserved. The studies outlined in this proposal have the potential to significantly advance our understanding of neural stem cell differentiation, with high impact in the field of developmental neurobiology.