THE ANALYSIS OF PATHOGENESIS OF AMYOTROPHIC LATERAL SCLEROSIS BASED ON THE ESTABLISHMENT OF IN VITRO MOTOR NEURONAL CELL LINES

先前关于神经元多样化问题的研究表明，中枢神经系统内神经元身份的规范是由几种环境信号的局部作用控制的。这些信号分子通过诱导细胞内在信号分子的表达来确定邻近细胞的身份，其中许多是转录因子。而这些转录因子，反过来，调节下游基因的表达以获得单个神经元的身份。众所周知，Sonic hedgehog （Shh）是一种触发运动神经元分化的信号分子，但人们对Shh的作用与运动神经元身份规范之间的干预步骤知之甚少。我对来自单个早期指定运动神经元的cDNA文库进行了差异筛选，并鉴定了一种新的同源盒基因MNR2，该基因由运动神经元祖细胞表达，并在有丝分裂后运动神经元中短暂表达。在体内发育中的脊髓中，MNR2的异位表达被证明启动了运动神经元分化程序。以运动神经元转录因子的表达、神经递质表型和轴突轨迹为特征。这些结果表明，sh介导的单一转录因子MNR2的诱导足以指导运动神经元的分化。

Previous works concerning the issues of neuronal diversification were able to show that the specification of neuronal identity within the CNS is controlled by the localized action of several environmental signals. These signaling molecules specify the identity of neighboring cells by inducing the expression of cell intrinsic signaling molecules, many of which are transcription factors. And these transcription factors, in turn, regulate expression of the downstream genes for the acquisition of the individual neuronal identities.Sonic hedgehog (Shh) is known to be a signaling molecule that trigger the differentiation of motor neurons, but the intervening steps between the actions of Shh and the specification of motor neuron identity were poorly understood. I have employed a differential screen of a cDNA library derived from a single early-specified motor neuron, and have identified a novel homeobox gene, MNR2, expressed by motor neuron progenitor cells and transiently by postmitotic motor neurons. The ectopic expression of MNR2 in the developing spinal cord in vivo was shown to initiate a program of motor neuron differentiation. characterized by the expression of motor neuron transcription factors, by neurotransmitter phenotype, and by axonal trajectory. These results indicate that the Shh-mediated induction of a single transcription factor, MNR2, is sufficient to direct the motor neuron differentiation.