Department of Biochemistry and Molecular Biology, Cumming School of Medicine, Alberta Children's Hospital Research Institute, University of Calgary, 3330 Hospital Drive, Calgary, AB, T2N 4N1, Canada.
Department of Biochemistry and Molecular Biology, Cumming School of Medicine, Alberta Children's Hospital Research Institute, University of Calgary, 3330 Hospital Drive, Calgary, AB, T2N 4N1, Canada.
Dev Biol. 2022 Sep;489:1-13. doi: 10.1016/j.ydbio.2022.05.010. Epub 2022 May 24.
During neural development, progenitor cells generate different types of neurons in specific time windows. Despite the characterisation of many of the transcription factor networks involved in these differentiation events, the mechanism behind their temporal regulation is poorly understood. To address this question, we studied the temporal differentiation of the simple lateral floor plate (LFP) domain in the zebrafish spinal cord. LFP progenitors generate both early-born Kolmer-Agduhr" (KA") interneuron and late-born V3 interneuron populations. Analysis using a Notch signalling reporter demonstrates that these cell populations have distinct Notch signalling profiles. Not only do V3 progenitors receive higher total levels of Notch response, but they collect this response over a longer duration compared to KA" progenitors. To test whether the duration of Notch signalling determines the temporal cell fate specification, we combined a transgene that constitutively activates Notch signalling in the ventral spinal cord with a heat shock inducible Notch signalling terminator to switch off Notch response at any given time. Sustained Notch signalling results in expanded LFP progenitors while KA" and V3 interneurons fail to specify. Early termination of Notch signalling leads to exclusively KA" cell fate, despite the high level of Notch signalling, whereas late attenuation of Notch signalling drives only V3 cell fate. This suggests that the duration of Notch signalling, not simply the level, mediates cell fate specification. Interestingly, knockdown experiments reveal a role for the Notch ligand Jag2b in maintaining LFP progenitors and limiting their differentiation into KA" and V3 interneurons. Our results indicate that Notch signalling is required for neural progenitor maintenance while a specific attenuation timetable defines the fate of the postmitotic progeny.
在神经发育过程中，祖细胞在特定的时间窗口中产生不同类型的神经元。尽管已经鉴定出许多参与这些分化事件的转录因子网络，但它们的时间调节机制仍知之甚少。为了解决这个问题，我们研究了斑马鱼脊髓中简单的侧基板（LFP）区域的时间分化。LFP 祖细胞产生早期出生的 Kolmer-Agduhr“（KA”）中间神经元和晚期出生的 V3 中间神经元群体。使用 Notch 信号报告基因的分析表明，这些细胞群体具有不同的 Notch 信号特征。不仅 V3 祖细胞接收更高水平的总 Notch 反应，而且与 KA“祖细胞相比，它们在更长的时间内收集这种反应。为了测试 Notch 信号的持续时间是否决定了时间细胞命运指定，我们将一种在腹侧脊髓中组成型激活 Notch 信号的转基因与热休克诱导的 Notch 信号终止子结合使用，以在任何给定时间关闭 Notch 反应。持续的 Notch 信号导致 LFP 祖细胞扩张，而 KA“和 V3 中间神经元无法指定。 Notch 信号的早期终止导致仅 KA“细胞命运，尽管 Notch 信号水平很高，但 Notch 信号的晚期衰减仅驱动 V3 细胞命运。这表明 Notch 信号的持续时间，而不仅仅是水平，介导细胞命运指定。有趣的是， knockdown 实验表明 Notch 配体 Jag2b 在维持 LFP 祖细胞和限制其分化为 KA“和 V3 中间神经元方面起作用。我们的结果表明 Notch 信号对于神经祖细胞的维持是必需的，而特定的衰减时间表定义了有丝分裂后祖细胞的命运。
