Helix-Loop-Helix Proteins and Vertebrate Neurogenesis

描述（申请人提供）：碱性-螺旋-环-螺旋（bHLH）转录因子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，在神经祖细胞或未分化的胚胎癌细胞中，这些蛋白的强制表达可以启动细胞周期退出和神经元分化。我们的数据表明bHLH蛋白增加了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、bHLH蛋白强制表达以及小鼠大脑皮层神经元分化中的作用。此外，我们将描述CDKi表达受神经bHLH蛋白调节的机制。

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.