Pathogenic mutations in the solute carrier family 7 member 5 (SLC7A5) gene which encodes an amino acid transporter cause microcephaly and seizures, yet the mechanisms responsible for these phenotypes are unclear. Models have demonstrated that Slc7a5 deletion is embryonic lethal and that these embryos lack a fully formed telencephalon. This phenotype is similar to that of mammalian Target of Rapamycin (mTOR) protein kinase deletion or mTOR inhibition. Notably, in many cells, Slc7a5 import of amino acids is required to maintain mTOR activity. Slc7a5 is present within neurogenic regions during embryogenesis, is found in cultured neurons, and can modulate neuronal electrophysiological properties. However, Slc7a5 is also highly expressed within endothelial cells of the blood brain barrier where removal in conditional mice leads to severe behavioral defects and non-cell autonomous changes in neurons. Therefore, the extent that neural Slc7a5 is required for development is unclear. Here, subventricular zone neural stem cells that generate olfactory bulb granule cell (GC) neurons were electroporated with SLC7A5 or Slc7a5 shRNA encoding plasmids. Although early phases of neural development were unaltered, Slc7a5 knockdown effected late phases of GC dendrite maturation and survival. Slc7a5 knockdown also decreased mTOR pathway activity. Rheb, an mTOR activator, rescued the effect of Slc7a5 knockdown on mTOR pathway activity and dendrite arbors. The data presented here demonstrate that Slc7a5 is required for GC mTOR pathway activity, maturation, and survival which may help explain why Slc7a5 mutations prevent normal brain development and function.

中文翻译：

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氨基酸转运蛋白 Slc7a5 调节 mTOR 通路，是颗粒细胞发育所必需的。

编码氨基酸转运蛋白的溶质载体家族 7 成员 5 ( SLC7A5 ) 基因的致病性突变会导致小头畸形和癫痫发作，但导致这些表型的机制尚不清楚。模型已证明Slc7a5缺失会导致胚胎死亡，并且这些胚胎缺乏完全形成的端脑。这种表型与哺乳动物雷帕霉素靶点 ( mTOR ) 蛋白激酶缺失或 mTOR 抑制相似。值得注意的是，在许多细胞中，需要 Slc7a5 输入氨基酸来维持 mTOR 活性。Slc7a5 在胚胎发生过程中存在于神经发生区域内，存在于培养的神经元中，并且可以调节神经元的电生理特性。然而，Slc7a5 在血脑屏障的内皮细胞内也高度表达，在有条件的小鼠中去除该内皮细胞会导致严重的行为缺陷和神经元的非细胞自主变化。因此，神经Slc7a5对于发育的需要程度尚不清楚。在这里，用 SLC7A5 或 Slc7a5 shRNA 编码质粒电穿孔产生嗅球颗粒细胞 (GC) 神经元的室下区神经干细胞。尽管神经发育的早期阶段没有改变，但 Slc7a5 敲低影响了 GC 树突成熟和存活的后期阶段。Slc7a5 敲低也降低了 mTOR 通路活性。Rheb 是一种 mTOR 激活剂，可挽救 Slc7a5 敲低对 mTOR 通路活性和树突乔木的影响。这里提供的数据表明，Slc7a5 是 GC mTOR 通路活性、成熟和存活所必需的，这可能有助于解释为什么 Slc7a5 突变会阻止正常的大脑发育和功能。