Gene Regulation in the Cell Commitment and Differentiation

基于1991年至1992年的研究结果，我们利用老年鸡胚色素上皮细胞(PECs)的晶状体转分化系统，分析了被认为是决定多潜能未分化细胞分化的基因的调控机制。此外，我们还合作找出了哺乳动物中枢神经系统发育和分化的调节机制。结果表明，在允许条件下，老年鸡胚的PECs可以通过多能去分化细胞(DePECs)向晶状体细胞转分化。PP344和pP64两个基因被发现是维持PECs稳定分化状态和晶状体转分化所必需的。对这两个基因的结构和功能的分析表明，pP344基因的产物具有蛋白酶抑制活性，是特异表达的…更多地由视网膜PECs发挥作用，并通过与PECs本身的细胞外基质成分的协同作用而发挥调节分化状态的重要作用。PP64基因被发现编码TGFbeta结合蛋白，通过其mRNAs的选择性剪接产生5.0kb和6.0kb的转录本。分化良好的PECs除表达6.0kb的mRNAs外，还表达5.0kb的mRNAs。5.0kb的mRNAs产生的蛋白质由PECS原位分泌，而6.0kb的mRNAs产生的蛋白质被PECS细胞外基质捕获。此外，在多能的dePECs和转分化的晶状体细胞中，pP344完全失活，仅表达6.0kb的pP64基因产物。此外，由PECs、dePECs和晶状体细胞产生的bFGF和TGFbeta被发现负责调节PEC的分化状态。除了这一发现表明小鼠中枢神经系统发育过程中发生基因重排的可能性很大之外，这些发现还必须为前瞻性研究提供必要的信息，以了解决定多潜能未分化细胞在发育过程中分化的分子机制。较少

Based on the findings established through studies from 1991 to 1992, we have analyzed the regulatory mechanisms of genes which are thought to be responsible for determination of differentiation in multipotent undifferentiated cells, using the system of lens transdifferentiation of pigmented epithelial cells (PECs) of older chick embryos. In addition, we have collaborated to find out the mechanism regulating development and differentiation of the central nervous system in mammals. The following results were obtained.PECs from older chick embryos can readily transdifferentiate to lens cells via multipotent dedifferentiated cells (dePECs) under the permissive condition. Two genes, designated as pP344 and pP64, were found to be required for stable maintenance of differentiated states and lens transdifferentiation of PECs. Analyses of structure and function of these two genes have revealed that the product of pP344 gene exhibited the activity as a protease inhibitor, was expressed specifica … More lly by the retinal PECs, and play an essential role to regulate the differentiated state through cooperative functions with extracellular matrix components of PECs themselves. The pP64 gene, which was found to encodes TGFbeta-binding proteins, produced 5.0kb and 6.0kb transcripts by alternative splicing of its mRNAs. The well-differentiated PECs express 5.0kb mRNAs as major product in addition to 6.0kb mRNAs. The protein produced by 5.0kb mRNAs is secreted by PECs in situ but that produced by 6.0kb mRNAs is trapped by the extracellular matrix of PECs. In addition, in the multipotent dePECs and transdifferentiated lens cells the pP344 is completely inactivated and 6.0kb product of the pP64 gene is only expressed. Moreover, bFGF and TGFbeta, which is produced by PECs, dePECs and also lens cells, were found to be responsible for regulation of the differentiated state of PECs.In addition to the finding to suggest the strong possibility of occurrence of gene rearrangement during development of the central nervous system in mice, the findings avobe described must provide the essential information required for the prospective studies to understand the molecular mechanism which rules determination of differentiation of multipotent undifferentiated cells during development. Less