Silverman T, Rein A, Orrison B, Langloss J, Bratthauer G, Miyazaki J, Ozato K
Laboratory of Developmental and Molecular Immunity, Institute of Child Health and Human Development, Bethesda, MD 20892.
J Immunol. 1988 Jun 15;140(12):4378-87.
To study the regulation of MHC class I gene expression during embryonic development, we have characterized a number of clonal cell lines derived from somite stage mouse embryos that were established with or without infection by several transforming retroviruses in combination with murine leukemia viruses. Unlike embryonal carcinoma (EC) cells that have been used as a model for early embryos, the cell lines derived from somite stage embryos are negative for stage specific embryonic Ag-1 and do not appear to differentiate after retinoic acid treatment. Morphology varies from clone to clone and is distinct from that of F9 and other EC cells. In agreement with previous findings in in vivo embryos, expression of surface MHC class I antigen in 57 new clones is either undetectable or low (with variability). All of the clones respond to the addition of interferons and express MHC class I antigens at high levels, but the kinetics of mRNA accumulation vary considerably. To examine the basis of the generally low or absent MHC class I gene expression in these cells, we tested promoter activity of a MHC class I gene by CAT assay after transient DNA transfection. Regardless of the basal levels of mRNA or surface Ag, CAT activity directed by various portions of the 5' flanking region of the MHC class I gene was uniformly low. The cells showed neither the negative nor the positive regulation of MHC class I genes that had been noted respectively for EC cells and for cells expressing the Ag constitutively. The pattern seen in the new cell lines suggests that there is an intermediate stage in the developmental regulation of MHC class I gene expression that may operate during the middle to late stage of fetal development.
为研究胚胎发育过程中MHC I类基因表达的调控机制，我们对一些源自体节期小鼠胚胎的克隆细胞系进行了特性分析。这些细胞系是在有或无几种转化逆转录病毒与鼠白血病病毒联合感染的情况下建立的。与被用作早期胚胎模型的胚胎癌细胞（EC）不同，源自体节期胚胎的细胞系对阶段特异性胚胎抗原-1呈阴性，并且在视黄酸处理后似乎不会分化。各克隆的形态各不相同，且与F9及其他EC细胞的形态不同。与先前在体内胚胎中的研究结果一致，57个新克隆中表面MHC I类抗原的表达要么无法检测到，要么水平较低（存在变异性）。所有克隆均对干扰素的添加有反应，并高水平表达MHC I类抗原，但mRNA积累的动力学差异很大。为研究这些细胞中MHC I类基因表达普遍较低或缺失的原因，我们在瞬时DNA转染后通过CAT分析测试了MHC I类基因的启动子活性。无论mRNA或表面抗原的基础水平如何，MHC I类基因5'侧翼区域不同部分所指导的CAT活性均一致较低。这些细胞既未表现出在EC细胞中分别观察到的MHC I类基因的负调控，也未表现出在组成性表达该抗原的细胞中观察到的正调控。在新细胞系中观察到的模式表明，MHC I类基因表达的发育调控存在一个中间阶段，该阶段可能在胎儿发育的中后期起作用。
