Hamon-Benais C, Delagebeaudeuf C, Jeremiah S, Lecoq O, Cassio D
Centre National de la Recherche Scientifique, URA 1343, Institute Curie, Université de Paris-Sud, Orsay, France.
Exp Cell Res. 1994 Jul;213(1):295-304. doi: 10.1006/excr.1994.1201.
Fusion of hepatoma cells with cells of similar ploidy (1s) from different histogenetic origin results in the systematic and stable extinction of hepatic traits. However, doubling the ploidy of the hepatoma parent (2s) leads to the formation of hybrids in which extinction is not observed. To establish if these dosage effects reflect, as generally thought, the ineffectiveness of the extinguishers in 2s hepatoma-derived hybrids, the efficiency of a specific extinguisher was improved. Rat hepatoma cells (1s) stably and selectively extinguished for albumin, owing to the presence of a single mouse fibroblast chromosome marker M1, were fused with the original albumin producing hepatoma cells. In the dozen independent hybrid clones isolated, the M1 chromosome was retained and the rat albumin gene silenced. This proves that the albumin extinguisher is still efficient when the number of its targets is doubled. However the extinction promoted by this extinguisher was not immediate after fusion. A detailed analysis of the time course of extinction revealed that a precise number of cell divisions, seven, is required for the monochromosomal 2s hybrid cells to become extinguished. This phenotype was stable but reversible, loss of M1 chromosome leading to albumin expression. Moreover, the M1 part carrying the specific albumin extinguisher locus, Tse a, was identified as mouse chromosome 3.
将肝癌细胞与来自不同组织发生起源、具有相似倍性（1s）的细胞融合，会导致肝脏特征系统性且稳定地消失。然而，将肝癌亲代细胞的倍性加倍（2s）会导致杂种细胞的形成，在这些杂种细胞中未观察到特征消失。为了确定这些剂量效应是否如通常所认为的那样，反映了2s肝癌衍生杂种细胞中消除因子的无效性，提高了一种特定消除因子的效率。由于存在单个小鼠成纤维细胞染色体标记M1而稳定且选择性地消除白蛋白的大鼠肝癌细胞（1s），与产生白蛋白的原始肝癌细胞融合。在分离出的十几个独立杂种克隆中，M1染色体得以保留，而大鼠白蛋白基因沉默。这证明当消除因子的靶标数量加倍时，白蛋白消除因子仍然有效。然而，这种消除因子促进的特征消失在融合后并非立即发生。对特征消失时间进程的详细分析表明，单染色体2s杂种细胞要实现特征消失需要精确的细胞分裂次数，即七次。这种表型是稳定的但可逆，M1染色体的丢失会导致白蛋白表达。此外，携带特定白蛋白消除因子基因座Tse a的M1部分被确定为小鼠3号染色体。
