Temporal Patterning of Neural Progenitors to Generate Neural Diversity

脊椎动物和无脊椎动物的神经前体细胞在时间上形成模式，以产生巨大的 神经类型的多样性与出生顺序有关。时间转录系列 果蝇神经母细胞中的因子(TTF)被发现是按顺序表达的，它们是 建议形成转录级联来控制不同神经元的顺序生成 类型。然而，从突变表型推断的交叉调节是否是直接的 转录调控尚未得到证实。此外，交叉法规 TTF之间的差异对于时间转换来说通常是不够的，这表明还有其他机制 起着调节时间进程的作用。我们利用果蝇的延髓神经母细胞 研究这些问题。在之前的R01时期，我们确定了分子机制 控制向SLP和EY时间阶段的过渡，并确定了一个全面的 通过单细胞RNA测序获得新的时间转录因子列表。在这次更新中 应用，我们给出了我们的单核ATAC序列的初步数据，它揭示了 在延髓神经母细胞的时间模式过程中染色质的动态可及性。穿过 分析差异可及区域，我们确定了可能的增强子控制 TTF基因的时间表达模式。通过整合scRNA-seq和 SnATACseq和报告分析、基因分析和Dam-ID实验的组合， 我们建议阐明控制序列的转录调控网络。 非常详细的时间转换。此外，我们发现不同的表观遗传因素是 在时间图案化的不同步骤中需要。我们建议进一步研究它们如何 调节动态染色质的可及性以及它们如何被招募到特定的靶基因 在时间模式形成过程中。最后，我们建议研究基本分子。 协调生长/增殖与TTF级联过程的机制，并将测试 我们的假设：早期的TTF在控制生长/增殖方面的作用与晚期不同 通过多种方法进行的专题信托基金。

Vertebrate and invertebrate neural progenitors are temporally patterned to generate a great diversity of neural types in a birth-order dependent manner. Series of temporal transcription factors (TTF) were found to be sequentially expressed in Drosophila neuroblasts, and they are proposed to form transcriptional cascades to control the sequential generation of different neural types. However, whether the cross-regulations inferred from mutant phenotypes are direct transcriptional regulations haven't been demonstrated. Furthermore, the cross-regulations among TTFs are often not sufficient for the temporal transitions, suggesting other mechanisms are at play to regulate the temporal progression. We use the Drosophila medulla neuroblasts to study these questions. In the previous R01 period, we identified molecular mechanisms controlling transitions to the Slp and Ey temporal stages, and also identified a comprehensive list of novel temporal transcription factors through single-cell RNA sequencing. In this renewal application, we present our preliminary data of single-nuclear ATAC seq, which revealed the dynamic chromatin accessibility during temporal patterning of medulla neuroblasts. Through analyzing the differentially accessible regions, we identified the possible enhancers controlling the temporal expression patterns of TTF genes. Through integration of scRNA-seq and snATACseq and a combination of reporter assays, genetic analysis and Dam-ID experiments, we propose to elucidate the transcriptional regulatory networks controlling the sequential temporal transitions in great detail. Furthermore, we found that different epigenetic factors are required at different steps of temporal patterning. We propose to further examine how they regulate the dynamic chromatin accessibility and how they are recruited to specific target genes during temporal patterning. Finally, we propose to examine the fundamental molecular mechanisms that coordinate the growth/proliferation with TTF cascade progression, and will test our hypothesis that early TTFs have different roles in controlling growth/proliferation than late TTFs through a combination of approaches.