Helix-Loop-Helix Proteins and Vertebrate Neurogenesis

描述（由申请人提供）：转录因子的碱性-螺旋-环-螺旋（bHLH）家族是脊椎动物神经元形成和分化的关键调节因子。神经bHLH蛋白是小鼠神经元形成所必需的，并且这些蛋白的强制表达可以启动神经祖细胞或未定型胚胎癌细胞中的细胞周期退出和神经元分化。我们的数据表明，bHLH蛋白增加至少一种细胞周期蛋白依赖性激酶抑制剂（CDKi）的表达，这可能有助于神经元细胞周期退出。在这里，我建议进一步分析CDKi蛋白在神经元细胞周期退出中的作用，在响应强制表达的bHLH蛋白和在分化神经元从小鼠大脑皮层。此外，我们将表征神经bHLH蛋白调节CDKi表达的机制。 在神经元分化过程中，神经bHLH蛋白以连续级联方式表达，其中一些bHLH蛋白在神经祖细胞中表达，而另一些在分化过程中表达。目前尚不清楚在神经元分化过程中表达的bHLH蛋白是否具有与在神经前体中表达的那些bHLH蛋白不同的功能。为了解决这个问题，我们将确定是否neuroD家族的bHLH蛋白，这是在神经元分化过程中表达的成员，是功能上需要的神经前体bHLH蛋白，如neurogenin 1下游介导细胞周期退出和神经元分化。这些研究，以及我们对CDKi功能的研究，将有助于我们最近开发的基于哺乳动物表达载体的RNA干扰方法。 这项研究将有助于更好地了解哺乳动物（包括人类）神经发生和神经元分化的调节机制。从长远来看，这些信息应该有助于制定替代因损伤或神经退行性疾病而丢失的神经元的策略。

DESCRIPTION (provided by applicant): The basic-helix-loop-helix (bHLH) family of transcription factors are key regulators of neuron formation and differentiation in vertebrates. Neural bHLH proteins are required for neuron formation in the mouse, and forced expression of these proteins can initiate cell cycle withdrawal and neuronal differentiation in neural progenitors or uncommitted embryonic carcinoma cells. Our data indicates that the bHLH proteins increase expression of at least one cyclin-dependent-kinase inhibitor (CDKi), and this is likely to contribute to neuronal cell cycle exit. Here I propose to further analyze the role of CDKi proteins in neuronal cell cycle exit, in response to forced expression of bHLH proteins and in differentiating neurons from the mouse cerebral cortex. In addition, we will characterize the mechanism(s) by which CDKi expression is regulated by the neural bHLH proteins. During neuronal differentiation, neural bHLH proteins are expressed in a sequential cascade, with some bHLH proteins expressed in neural progenitors and others expressed during differentiation. It is not known if the bHLH proteins expressed during neuronal differentiation have functions distinct from those bHLH proteins expressed in neural precursors. To address this question, we will determine whether members of the neuroD family of bHLH proteins, which are expressed during neuronal differentiation, are functionally required downstream of neural precursor bHLH proteins such as neurogenin 1 to mediate cell cycle exit and neuronal differentiation. These studies, as well as our studies on CDKi function, will be facilitated by a mammalian expression vector-based method for RNA interference that we have recently developed. This research should lead to a better understanding of the mechanisms that regulate neurogenesis and neuronal differentiation in mammals, including humans. In the long term, such information should contribute to developing strategies for replacement of neurons lost due to injury or neurodegenerative diseases.