[Cytogenetic studies of X-chromosome replication patterns in cell hybrids between murine embryonal carcinoma cells and female rat thymocytes].
By means of a 5-bromodeoxyuridine incorporation and acridine orange fluorescence staining method together with 3H-thymidine autoradiography, I studied the chronology of X chromosome replication in newly formed cell hybrids between the hypoxanthine phosphoribosyl transferase-deficient OTF9-63 murine embryonal carcinoma cell and the female rat thymocyte. Most near-tetraploid hybrid cells retained all chromosomes from both parents including one mouse X and two rat X chromosomes throughout the period of this study. Data showing changes in the chronology of X chromosome replication obtained here were indicative of reactivation of the inactive X chromosome from the rat thymocyte, and de novo X-inactivation of one or two X chromosomes. The extinction of lymphocyte phenotypes from the hybrids and their subsequent differentiation to the cell type resembling endoderm found in the peri-implantation mouse embryo were apparently in parallel with the above changes. These data thus demonstrated that there is a close causal correlation between the X-inactivation process and the cell differentiation.
D000818:Animals; D002453:Cell Cycle; D002454:Cell Differentiation; D005260:Female; D006822:Hybrid Cells; D008938:Mitosis; D051381:Rats; D013601:T-Lymphocytes / Q000648:ultrastructure*; D013724:Teratoma / Q000235:genetics*; D014960:X Chromosome