Stress-activated protein kinase MKK7 regulates axon elongation in the developing cerebral cortex
Stress-activated protein kinase MKK7 regulates axon elongation in the developing cerebral cortex
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DOI：
10.1523/jneurosci.1111-11.2011
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发表时间：
2011-09
影响因子：
2.9
通讯作者：
Tokiwa Yamasaki;H. Kawasaki;H. Nishina
中科院分区：
文献类型：
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作者：
Tokiwa Yamasaki;H. Kawasaki;H. Nishina
c-Jun氨基末端蛋白激酶（JNK）属于丝裂原活化蛋白激酶家族，在多种生理过程中发挥重要作用。JNK由两个上游调节因子，丝裂原活化蛋白激酶激酶（MKK）7和MKK 4控制。为了阐明MKK 7的生理功能，我们使用Nestin-Cre产生一种新的小鼠模型，其中mkk 7基因在神经系统中特异性缺失（Mkk 7 flox/flox Nestin-Cre小鼠）。这些小鼠在胚胎发育期间的大体外观与其对照同窝小鼠没有区别，但出生后立即死亡，没有呼吸。组织学检查显示，突变体在脑发育方面存在严重缺陷，包括脑室扩大，纹状体减少和轴突束减少。电镜观察发现Mkk 7 flox/flox Nestin-Cre脑内丝状结构和自噬空泡异常聚集。进一步的分析表明，MKK 7缺失减少了大脑中TAG-1表达轴突的数量和延迟的神经元迁移。神经元分化没有改变。子宫内电穿孔研究表明，在MKK 7的情况下，第2/3层神经元的轴突对侧投射受损。此外，MKK 7在体内以细胞自主的方式调节轴突伸长，这一发现在体外得到证实。最后，JNK底物的磷酸化水平，包括c-Jun，神经丝重链，微管相关蛋白1B和doublecortin，在Mkk 7 flox/flox Nestin-Cre脑中降低。我们的研究结果表明，Mkk 7 flox/flox Nestin-Cre小鼠的表型与Mkk 4flox/flox Nestin-Cre小鼠的表型有很大不同，并确定MKK 7介导的JNK调节对于发育中的脑中轴突伸长和径向迁移都是唯一关键的。
The c-Jun NH2-terminal protein kinase (JNK), which belongs to the mitogen-activated protein kinase family, plays important roles in a broad range of physiological processes. JNK is controlled by two upstream regulators, mitogen-activated protein kinase kinase (MKK) 7 and MKK4. To elucidate the physiological functions of MKK7, we used Nestin-Cre to generate a novel mouse model in which the mkk7 gene was specifically deleted in the nervous system (Mkk7flox/flox Nestin-Cre mice). These mice were indistinguishable from their control littermates in gross appearance during embryogenesis but died immediately after birth without breathing. Histological examination showed that the mutants had severe defects in brain development, including enlarged ventricles, reduced striatum, and minimal axon tracts. Electron microscopy revealed abnormal accumulations of filamentous structures and autophagic vacuoles in Mkk7flox/flox Nestin-Cre brain. Further analysis showed that MKK7 deletion decreased numbers of TAG-1-expressing axons and delayed neuronal migration in the cerebrum. Neuronal differentiation was not altered. In utero electroporation studies showed that contralateral projection of axons by layer 2/3 neurons was impaired in the absence of MKK7. Moreover, MKK7 regulated axon elongation in a cell-autonomous manner in vivo, a finding confirmed in vitro. Finally, phosphorylation levels of JNK substrates, including c-Jun, neurofilament heavy chain, microtubule-associated protein 1B, and doublecortin, were reduced in Mkk7flox/flox Nestin-Cre brain. Our findings demonstrate that the phenotype of Mkk7flox/flox Nestin-Cre mice differs substantially from that of Mkk4flox/flox Nestin-Cre mice, and establish that MKK7-mediated regulation of JNK is uniquely critical for both axon elongation and radial migration in the developing brain.