Network of proneural basic helix-loop-helix transcription factors for regualtion of pulmonary neuroendocrine cells.

在本研究中，我们利用缺失哺乳动物Ahaete scute Complex(Mash1)和Hes1(Hes1)的哺乳动物同源基因的突变小鼠，研究了原生碱性螺旋-环-螺旋转录因子对肺神经内分泌细胞(PNEC)分化的意义，并评价了Notch信号系统在决定肺上皮细胞分化中的作用。免疫组织化学研究显示，PNEC Mash1阳性，而Hes1不阳性。相反，非神经内分泌细胞(NPNEC)Mash1阴性，Hes1阳性。Mash1基因敲除小鼠肺组织中未检测到PNEC，而Hes1基因敲除小鼠肺组织中可见PNEC增殖。将Mash1基因导入小鼠胎肺原代上皮细胞，可诱导出具有神经内分泌表型的细胞。此外，免疫组织化学研究显示，PNEC表达Notch配体Delta-like 1(Dll1)，但不表达Notch受体和配体(Jagged1和Jagged2)。NPNEC D111阴性，Notch1-3、Jagged1、Jagged2阳性。在Mash1基因缺失的小鼠肺组织中未检测到Dll1基因的表达，而在Hes1基因缺失的小鼠肺组织中，Notch1和Jagged1mRNAs的表达减少，因此，小鼠呼吸道上皮细胞的分化受基本螺旋-环-螺旋因子网络的调节，而Notch信号通路可能在肺上皮细胞的命运决定中发挥作用。

In the present study, we investigated the significance of pronueral basic helix-loop-helix transcription factors for the differentiation of pulmonary neuroendocrine cells (PNEC) using the mutant mice difcient of the genes of mammalian homolog of achaete scute complex (Mash1) and hairy and Enhancer of split (Hes1), and evaluated involvement of Notch signalling system in the determiantion of pulmonary epithelial cell differentiation.Immunohistochemical studies revealed that PNEC were positive for Mash1, but not for Hes1. In the contrary, non-neuroendocrine cells (NPNEC) were negative for Mash1, but positive for Hes1. In the mouse lungs from Mash1 null mice, PNEC were not detected, while in the mice lungs from Hes1 null mice, hyperplasia of PNEC was observed. When primary epithelial culture cells obtained from mouse fetal lungs were trasfected with Mash1 gene, cells with neuroendocrine phenotypes were induced. Moreover, immunohistochemical studies revealed that PNEC were positive for Delta-like 1 (Dll1), a Notch ligand, but not for Notch receptors and ligands (Jagged1 and Jagged2). In the contrary, NPNEC were negative for Dll1, but positive for Notch1-3, Jagged1 and Jagged2. In the mouse lungs from Mash1 null mice, Dll1 mRNA was not detected, while in the mice lungs from Hes1 null mice, expression of Notch1 and Jagged1 mRNAs was reduced.Thus, differentiation of mouse airway epithelial cells is regulated by a network of basic helix-loop-helix factors, and Notch signalling pathway could work in the cell fate determination of lung epithelial cells.