中文摘要：

目的 通过检测神经干细胞分化过程中抑制型和激活型碱性螺旋（bHLH）转录调控因子mRNA的表达，探讨神经干细胞定向分化机制。方法 小鼠胎脑细胞原代培养并鉴定。用全反义维甲酸（RA）诱导神经干细胞分化，通过反转录聚合酶链反应（RT-PCR）检测神经干细胞分化前以及分化后1d、2d、3d、5d和10d时Hesl、Hess、Mashl、Mathl及NeumDmRNA的表达。结果 HeslmRNA在神经干细胞分化前后均表达，无显著差异；HessmRNA随分化时间延长表达下降；NeuroDmRNA和MashlmRNA仅在已分化神经元中表达；MathlmRNA在分化后期表达明显。结论 神经干细胞分化过程中bHLH转录因子mRNA的表达具有明显的时相性，这将为最终揭示神经干细胞分化调控机制提供实验基础。

英文摘要：

Objective To investigate the differentiation nmchanisms of neural stem cells （NSCs） by determining expression of the basic helix-loop-helix （bHLH） genes. Methods The cells from the embryonic mouse brain were primarily cultured and identified. The NSCs were induced to differentiate by retinoic acid （RA）. Reverse Wancrfiptase-polymemse chain reaction（RT-PCR） was used to detect the expression of Hesl, HesS, Mashl, Mathl and NeuroD mRNA in NSCs before differentiation and at 1 d, 2 d, 3 d, 5 d or 10 d after differentiation, respectively. Results Hesl mRNA was present in undifferentiated and differentiated NSCs. Expression of Hess mRNA decreased with time. NeuroD and Mashl mRNA were expressed in differentiated NSCs. Mashl was highly expressed after induction with RA for 1 d. NeuroD was highly expressed after induction with RA for two days. Conclusion The expression pattern of mRNA of bHLH genes is detected, which may contribute to explain the mechanisms of differentiation of NSCs.