The transcription factor HHEX as a novel regulator of CNS axon regeneration

 描述(申请人提供)：在这里，我们试图阐明一种称为HHEX的转录因子限制神经元延长轴突能力的分子机制，并探索干扰HHEX功能促进中枢神经系统轴突生长的可能性。这项工作意义重大，因为中枢神经系统神经元再生能力低，阻碍了中风、神经退行性疾病或脑或脊髓损伤的完全恢复。一个主要的治疗目标是增强中枢神经系统神经元的再生能力，但限制生长的分子机制仍不完全清楚。HHEX与神经系统外细胞的细胞生长有关，但在大脑中基本上没有研究，它出人意料地出现在一项大规模的筛选实验中，该实验考察了各种转录因子对皮质神经元形态的影响。HHEX的表达强烈抑制轴突生长。此外，HHEX在再生不良的成年中枢神经系统神经元中表达，但在周围神经系统中再生能力强的神经元中不表达。最后，结构-功能分析显示，HHEX通过抑制靶基因来阻止轴突生长，并且激活HHEX靶基因的人工构建逆转了正常的活动，即促进轴突生长。综上所述，这些数据表明，HHEX是一种抑制中枢神经系统神经元轴突生长能力的新因子，而操纵HHEX功能可以促进轴突生长。在这项资助中，我们将1)阐明HHEX调控的一组基因，以阐明生长抑制的机制；2)测试基于HHEX的操作在脊髓损伤动物模型中促进轴突萌发和再生的能力。最终，这些研究将通过识别调控中枢神经系统再生的新转录成分来填补该领域知识的关键空白，并探索这一新靶点提高再生能力的潜力。

 DESCRIPTION (provided by applicant): Here we seek to clarify the molecular mechanisms by which a transcription factor called HHEX restricts the ability of neurons to extend axons, and explore the potential of interfering with HHEX function to promote axon growth in the central nervous system. This work is significant because the low regenerative ability of neurons in the central nervous system prevents full recovery from stroke, neurodegenerative disease, or injury to the brain or spinal cord. A major therapeutic goal is to enhance regenerative ability in CNS neurons, but the molecular mechanisms that restrict growth remain incompletely understood. HHEX, which has been linked to cellular growth in cells outside the nervous system but is largely unstudied in the brain, emerged unexpectedly from a large-scale screening experiment that examined the effect of various transcription factors on the morphology of cortical neurons. Expression of HHEX strongly decreases axon growth. Furthermore, HHEX is expressed in adult CNS neurons that regenerate poorly, but not in regeneration-competent neurons in the peripheral nervous system. Finally, a structure-function analysis revealed that HHEX blocks axon growth by suppressing target genes, and that an artificial construct that activates HHEX target genes reverses the normal activity, that is, enhances axon growth. Combined, these data suggest that HHEX acts as a novel factor that suppresses axon growth ability in CNS neurons, and that manipulating HHEX function can promote axon growth. In this grant we will 1) clarify the set of genes that are regulated by HHEX in order to clarify the mechanism of growth suppression and 2) test the ability of HHEX-based manipulations to promote axonal sprouting and regeneration in an animal model of spinal cord injury. Ultimately, these studies will fill a critical gap in knowledge in the field through the identification of novel transcriptional components that regulate CNS regeneration, and explore the potential of this new target to improve regenerative capacity.