Department of Biological Sciences, University of South Carolina, Columbia, SC 29208.
Quantshine Asset Mgmt. Co. Ltd, Shanghai 200082, China.
eNeuro. 2018 Feb 2;5(1). doi: 10.1523/ENEURO.0350-17.2018. eCollection 2018 Jan-Feb.
mutations cause lissencephaly (LIS), a severe developmental brain malformation. Much less is known about its role in the mature nervous system. LIS1 regulates the microtubule motor cytoplasmic dynein 1 (dynein), and as LIS1 and dynein are both expressed in the adult nervous system, Lis1 could potentially regulate dynein-dependent processes such as axonal transport. We therefore knocked out Lis1 in adult mice using tamoxifen-induced, Cre-ER-mediated recombination. When an actin promoter was used to drive Cre-ER expression (Act-Cre-ER), heterozygous Lis1 knockout (KO) caused no obvious change in viability or behavior, despite evidence of widespread recombination by a Cre reporter three weeks after tamoxifen exposure. In contrast, homozygous Lis1 KO caused the rapid onset of neurological symptoms in both male and female mice. One tamoxifen-dosing regimen caused prominent recombination in the midbrain/hindbrain, PNS, and cardiac/skeletal muscle within a week; these mice developed severe symptoms in that time frame and were killed. A different tamoxifen regimen resulted in delayed recombination in midbrain/hindbrain, but not in other tissues, and also delayed the onset of symptoms. This indicates that Lis1 loss in the midbrain/hindbrain causes the severe phenotype. In support of this, brainstem regions known to house cardiorespiratory centers showed signs of axonal dysfunction in KO animals. Transport defects, neurofilament (NF) alterations, and varicosities were observed in axons in cultured DRG neurons from KO animals. Because no symptoms were observed when a cardiac specific Cre-ER promoter was used, we propose a vital role for Lis1 in autonomic neurons and implicate defective axonal transport in the KO phenotype.
突变导致无脑回畸形（LIS），这是一种严重的发育性脑畸形。然而，关于其在成熟神经系统中的作用却知之甚少。LIS1 调节微管动力细胞质动力蛋白 1（dynein），并且由于 LIS1 和 dynein 都在成年神经系统中表达，因此 Lis1 可能潜在调节依赖 dynein 的过程，例如轴突运输。因此，我们使用他莫昔芬诱导的 Cre-ER 介导的重组在成年小鼠中敲除 Lis1。当使用肌动蛋白启动子驱动 Cre-ER 表达（Act-Cre-ER）时，杂合 Lis1 敲除（KO）尽管在他莫昔芬暴露后三周通过 Cre 报告基因证实广泛重组，但对存活率或行为没有明显影响。相比之下，纯合 Lis1 KO 导致雄性和雌性小鼠均迅速出现神经症状。一种他莫昔芬给药方案在一周内导致中脑/后脑、PNS 和心脏/骨骼肌肉中的明显重组；这些小鼠在那段时间内出现严重症状并被杀死。另一种不同的他莫昔芬方案导致中脑/后脑的重组延迟，但其他组织没有延迟，并且症状的发作也延迟。这表明 Lis1 在中脑/后脑中的缺失导致了严重的表型。支持这一观点的是，已知包含心肺中枢的脑干区域在 KO 动物中显示出轴突功能障碍的迹象。在从 KO 动物培养的 DRG 神经元的轴突中观察到运输缺陷、神经丝（NF）改变和静脉曲张。由于当使用心脏特异性 Cre-ER 启动子时没有观察到症状，因此我们提出 Lis1 在自主神经元中具有重要作用，并暗示轴突运输缺陷在 KO 表型中起作用。
