Reeve-Irvine Research Center, University of California, Irvine, United States; Department of Anatomy and Neurobiology, University of California, Irvine, United States; School of Medicine, University of California, Irvine, United States.
Reeve-Irvine Research Center, University of California, Irvine, United States; Department of Anatomy and Neurobiology, University of California, Irvine, United States; Department of Neurobiology and Behavior, University of California, Irvine, United States; Department of Neurosurgery, University of California, Irvine, United States; School of Medicine, University of California, Irvine, United States.
Exp Neurol. 2018 May;303:12-28. doi: 10.1016/j.expneurol.2018.01.005. Epub 2018 Jan 11.
Deletion of the phosphatase and tensin (PTEN) gene in neonatal mice leads to enlargement of the cell bodies of cortical motoneurons (CMNs) in adulthood (Gutilla et al., 2016). Here, we assessed whether PTEN deletion in adult mice would trigger growth of mature neurons. PTEN was deleted by injecting AAV-Cre into the sensorimotor cortex of adult transgenic mice with a lox-P flanked exon 5 of the PTEN gene and Cre-dependent reporter gene tdTomato. PTEN-deleted CMN's identified by tdT expression and retrograde labeling with fluorogold (FG) were significantly enlarged four months following PTEN deletion, and continued to increase in size through the latest time intervals examined (12-15 months post-deletion). Sholl analyses of tdT-positive pyramidal neurons revealed increases in dendritic branches at 6 months following adult PTEN deletion, and greater increases at 12 months. 12 months after adult PTEN deletion, axons in the medullary pyramids were significantly larger and G-ratios were higher. Mice with PTEN deletion exhibited no overt neurological symptoms and no seizures. Assessment of motor function on the rotarod and cylinder test revealed slight impairment of coordination with unilateral deletion; however, mice with bilateral PTEN deletion in the motor cortex performed better than controls on the rotarod at 8 and 10 months post-deletion. Our findings demonstrate that robust neuronal growth can be induced in fully mature cortical neurons long after the developmental period has ended and that this continuous growth occurs without obvious functional impairments.
在新生小鼠中删除磷酸酶和张力蛋白（PTEN）基因会导致成年皮质运动神经元（CMNs）的细胞体增大（Gutilla 等人，2016）。在这里，我们评估了成年小鼠中 PTEN 的缺失是否会触发成熟神经元的生长。通过将 AAV-Cre 注射到带有 PTEN 基因的lox-P 侧翼外显子 5和 Cre 依赖性报告基因 tdTomato 的成年转基因小鼠的感觉运动皮层中，从而删除 PTEN。通过 tdT 表达和逆行标记物氟金（FG）鉴定的 PTEN 缺失的 CMN 在 PTEN 缺失后四个月显着增大，并且通过检查的最新时间间隔继续增大（缺失后 12-15 个月）。 tdT 阳性锥体神经元的 Sholl 分析显示，成年 PTEN 缺失后 6 个月分支树突增加，12 个月时增加更多。成年 PTEN 缺失 12 个月后，延髓锥体中的轴突明显增大，G 比值更高。具有 PTEN 缺失的小鼠没有明显的神经症状和癫痫发作。在旋转棒和圆筒测试上评估运动功能发现，单侧缺失时协调能力略有受损；然而，在运动皮层中具有双侧 PTEN 缺失的小鼠在旋转棒上的表现优于对照组，在缺失后 8 个月和 10 个月时表现更好。我们的研究结果表明，在发育时期结束后很久，完全成熟的皮质神经元中可以诱导出强烈的神经元生长，并且这种持续的生长不会导致明显的功能障碍。
