Expression of Human and Suppression of Mouse Nucleolus Organizer Activity in Mouse-Human Somatic Cell Hybrids

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 73; no. 12; pp. 4531 - 4535
• Main Authors: Miller, Orlando J., Miller, Dorothy A., Dev, Vaithilingam G., Tantravahi, Ramana, Croce, Carlo M.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 01-12-1976; National Acad Sciences
• Subjects: Acrocentric chromosomes; Animals; Cell Line; Cell lines; Cell nucleolus; Cell Nucleolus - metabolism; Chromosomes; Chromosomes - metabolism; Diploidy; Human chromosomes; Humans; Hybrid cells; Hybrid Cells - metabolism; Hybrid Cells - ultrastructure; Hybridity; Karyotyping; Macrophages; Mice; Nucleolus organizer region; Ploidies; Somatic cells
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.73.12.4531

Most mouse-human somatic cell hybrids show preferential loss of human chromosomes, absence of human 28S ribosomal RNA, and suppression of human nucleolus organizer activity, as visualized by the Ag-AS silver histochemical stain. In contrast, the mouse-human hybrids studied here show preferential loss of mouse chromosomes. The hybrids were made by fusion of HT-1080-6TG human fibrosarcoma cells with BALB/c mouse peritoneal macrophages or strain 129 mouse teratocarcinoma cells. The Ag-AS staining method shows nucleolus organizer activity of chromosomes 13, 14, 15, 21 (rarely), and 22 in the human parent and chromosomes 12, 15, 16 (rarely), and 18 in the BALB/c mouse parent. In the hybrid cells the human nucleolus organizer regions are active, as shown by Ag-AS staining and involvement in ``satellite association.'' The mouse nucleolus organizer regions are not stained by the Ag-AS method even though mouse chromosomes 12, 15, and 18 are present in the BALB/c hybrids and at least one copy of each mouse chromosome is present in the teratocarcinoma-derived hybrids. Thus, in these mouse-human hybrids, unlike those that lose human chromosomes, only human nucleolus organizer activity is expressed, and mouse nucleolus organizer activity is suppressed.