Restoration of metabolic cooperation in heterokaryons between HGPRT-deficient mouse A9 fibroblasts and chick embryo erythrocytes.
Genetic determinants of metabolic cooperation were studied by fusing chick erythrocytes to HGPRT- mammalian cells. Heterokaryons were then tested for their ability to incorporate [3H]hypoxanthine and to transfer radioactive material to HGPRT- recipient cells. Chick erythrocytes (CE) have nuclei which are inactive but contain the HGPRT gene and some cytoplasmic HGPRT enzyme activity. They are unable, however, to cooperate with HGPRT- cells. Of the two mammalian cell lines used, the human GM29 line is HGPRT- and capable of functioning as a receptor cell in cooperation experiments with HGPRT+ cells. The HGPRT- mouse A9 line on the other hand is unable to cooperate. Immediately after fusion, both types of heterokaryons incorporated [3H]hypoxanthine, indicating the presence of some chick HGPRT enzyme contributed by the erythrocyte partner at the time of fusion. While the CE-GM29 heterokaryons participated in metabolic cooperation shortly after fusion, the CE-A9 heterokaryons did not. However, four days after fusion, i.e., at a time when the erythrocyte nucleus had been reactivated, the CE-A9 heterokaryons did cooperate. This suggests that in CE-A9 heterokaryons the genes required for metabolic cooperation are expressed by the previously dormant chick erythrocyte nucleus.
D000818:Animals; D001345:Autoradiography; D002460:Cell Line; D002642:Chick Embryo; D004912:Erythrocytes / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D006822:Hybrid Cells / Q000378:metabolism*; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics*; D007042:Hypoxanthines / Q000378:metabolism; D007926:Lesch-Nyhan Syndrome / Q000235:genetics*; D014316:Tritium
D007042:Hypoxanthines; D014316:Tritium; D007041:Hypoxanthine Phosphoribosyltransferase