THE REGULATORY EFFECT OF XENOPUS OOCYTE CYTOPLASM ON THE FUNCTIONAL ACTIVITY OF INJECTED MAMMALIAN NUCLEI / 解剖学报

ABSTRACT

The present study was designed to investigate the regulatory effect of Xenopus oocyte cytoplasm on the functional activity of the injected mammalian erythroid nuclei taken from different developmental stages and the tumor cell nuclei from human HeLa and mouse plasmocytoma (Sp 2/0) cell lines. Experimental results demonstrated that (1) only 1/3 of the injected erythroid nuclei derived from different physiological status survived and - were induced to become enlarged, accompanied by chromatin dispersion, clear nucleoplasm, and with the ability of incorporation of~3H-uridine for the synthesis of RNA, while most of the injected nuclei in pyknosis or in late differentiated stage were inactivated, stained black and degenerated steadily; (2) almost all the "injected tumor cell nuclei originally in active division of Sp 2/0 and HeLa survived and were activated by showing nuclei enlarged to about 10 to 200 times with fully chromatin dispersion, concomitant clear nucleoplasm and well developed nuclcoli. The state of activation is much more pronounced than that in erythroid nuclei; (3) isoelectrophoretic analysis of the oocytes with transplanted nuclei showed a dark band at pi 6.28 which is corresponding to a homologous component, but other than hemoglobin from rat bone marrow erythrocytes. It is suggested that the gene activities of the injected nuclei were reprogrammed by the oocyte cytoplasm, globin gene originally activated were closed and oocyte selected to open genes that suitable to host genetic state; (4) when injected into Xenopus oocyte with purified rat globin mRNA polyribosomes, it translated efficiently into hemoglobin. The above mentioned results could be concluded that the Xenopus oocyte provided favorable conditions for the translation of purified mRNA polysomes as well as to regulate or reprogram the expression of gones in the injected nuclei. The regulatory effect is closely related to the initial physiological status and the competence of the injected nuclei themselves responsed to oocyte cytoplasm, i.e. the efficiency is much more prominent in originally active proliferative nuclei than those in late or terminal differentiation.