Drosophila neuroblasts (NBs) are neural stem cells whose maintenance relies on Notch activity. NBs proliferate throughout larval stages to generate a large number of adult neurons. Their proliferation is protected under conditions of nutrition restriction but the mechanisms responsible are not fully understood. As amino acid transporters (Solute Carrier transporters, SLCs), such as SLC36, have important roles in coupling nutrition inputs to growth pathways, they may have a role in this process. For example, an SLC36 family transporter Pathetic (Path) that supports body size and neural dendrite growth in Drosophila, was identified as a putative Notch target in genome-wide studies. However, its role in sustaining stem cell proliferation and maintenance has not been investigated. This study aimed to investigate the function of Path in the larval NBs and to determine whether it is involved in protecting them from nutrient deprivation. The expression and regulation of Path in the Drosophila larval brain was analysed using a GFP knock-in allele and reporter genes containing putative Notch regulated enhancers. Path function in NB proliferation and overall brain growth was investigated under different nutrition conditions by depleting it from specific cell types in the CNS, using mitotic recombination to generate mutant clones or by directed RNA-interference. Path is expressed in both NBs and glial cells in the Drosophila CNS. In NBs, path is directly targeted by Notch signalling via Su(H) binding at an intronic enhancer, PathNRE. This enhancer is responsive to Notch regulation both in cell lines and in vivo. Loss of path in neural stem cells delayed proliferation, consistent with it having a role in NB maintenance. Expression from pathNRE was compromised in conditions of amino acid deprivation although other Notch regulated enhancers are unaffected. However, NB-expressed Path was not required for brain sparing under amino acid deprivation. Instead, it appears that Path is important in glial cells to help protect brain growth under conditions of nutrient restriction. We identify a novel Notch target gene path that is required in NBs for neural stem cell proliferation, while in glia it protects brain growth under nutrition restriction.

中文翻译：

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SLC36 转运蛋白 Pathetic 是神经干细胞增殖和营养限制下大脑生长所必需的。

果蝇成神经细胞 (NBs) 是神经干细胞，其维持依赖于 Notch 活性。NB 在整个幼虫阶段增殖以产生大量的成体神经元。它们的增殖在营养限制条件下受到保护，但相关机制尚不完全清楚。由于氨基酸转运蛋白（Solute Carrier transporters，SLCs），如 SLC36，在将营养输入耦合到生长途径中具有重要作用，因此它们可能在该过程中发挥作用。例如，支持果蝇体型和神经树突生长的 SLC36 家族转运蛋白 Pathetic (Path) 在全基因组研究中被确定为假定的 Notch 靶标。然而，其在维持干细胞增殖和维持方面的作用尚未得到研究。本研究旨在调查 Path 在幼虫 NBs 中的功能，并确定它是否参与保护它们免受营养剥夺。使用 GFP 敲入等位基因和含有推定的 Notch 调节增强子的报告基因，分析了果蝇幼虫大脑中 Path 的表达和调节。通过从中枢神经系统中的特定细胞类型中耗尽它，使用有丝分裂重组产生突变克隆或通过定向 RNA 干扰，在不同营养条​​件下研究了 NB 增殖和整体脑生长的路径功能。Path 在果蝇 CNS 的 NB 和神经胶质细胞中均有表达。在 NBs 中，Notch 信号通过在内含子增强子 PathNRE 上的 Su(H) 结合直接靶向路径。该增强子对细胞系和体内的 Notch 调节均有反应。神经干细胞中路径的丢失延迟了增殖，与其在 NB 维持中的作用一致。来自 pathNRE 的表达在氨基酸剥夺的条件下受到损害，尽管其他 Notch 调节增强子不受影响。然而，在氨基酸剥夺下，NB 表达的 Path 并不是大脑保留所必需的。相反，Path 在神经胶质细胞中似乎很重要，有助于在营养限制条件下保护大脑生长。我们确定了 NBs 中神经干细胞增殖所需的新型 Notch 靶基因路径，而在神经胶质细胞中，它在营养限制下保护大脑生长。来自 pathNRE 的表达在氨基酸剥夺的条件下受到损害，尽管其他 Notch 调节增强子不受影响。然而，在氨基酸剥夺下，NB 表达的 Path 并不是大脑保留所必需的。相反，Path 在神经胶质细胞中似乎很重要，有助于在营养限制条件下保护大脑生长。我们确定了 NBs 中神经干细胞增殖所需的新型 Notch 靶基因路径，而在神经胶质细胞中，它在营养限制下保护大脑生长。来自 pathNRE 的表达在氨基酸剥夺的条件下受到损害，尽管其他 Notch 调节增强子不受影响。然而，在氨基酸剥夺下，NB 表达的 Path 并不是大脑保留所必需的。相反，Path 在神经胶质细胞中似乎很重要，有助于在营养限制条件下保护大脑生长。我们确定了 NBs 中神经干细胞增殖所需的新型 Notch 靶基因路径，而在神经胶质细胞中，它在营养限制下保护大脑生长。