| Abstrakt: |
Genetic determinants of metabolic cooperation were studied by fusing chick erythrocytes to HGPRT mammalian cells. Heterokaryons were then tested for their ability to incorporate [H]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 [H]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 hetero-karyons 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. [ABSTRACT FROM AUTHOR] |
