ABSTRACT
Nuclear transplantations from several differentiated somatic cell types into amphibian oocytes and eggs revealed that their genome contains the genes required for the development of prefeeding tadpoles. In addition, erythrocyte nuclei directed the formation of feeding tadpoles (independent organisms) that advanced to larval stages with hind limb buds. Thus, the genome of several differentiated somatic cell types can undergo widespread activation and specify a multiplicity of cell types. Although evidence for the genetic totipotency of differentiated somatic cells is lacking, we speculate that the genetic totipotency of at least some differentiated somatic cell types still remains a tenable hypothesis.
Subject(s)
Gene Expression Regulation , Nuclear Transfer Techniques , Oocytes/metabolism , Amphibians , Animals , Cell Differentiation , PhenotypeABSTRACT
Diploid frog nuclei from differentiated somatic cells, transplanted into enucleated eggs to determine whether cell specialization generally involves irreversible genetic changes, have shown that nuclei from specialized somatic cells still contain the genes specifying the cell types and organ systems of swimming tadpoles. However, those tadpoles failed to feed and did not survive beyond the initial tadpole stages. Here we report that, after incubation in oocytes, triploid erythrocyte nuclei from juvenile frogs of Rana pipiens directed the formation of feeding tadpoles that survived up to a month and had differentiated hind limb buds. These tadpoles occurred at a high yield and showed the most extensive development so far obtained from documented differentiated somatic nuclei.
Subject(s)
Cell Differentiation , Cell Nucleus/physiology , Erythrocytes/physiology , Rana pipiens/genetics , Animals , Clone Cells , Genes , Larva , Nuclear Transfer Techniques , Rana pipiens/embryologyABSTRACT
Seven nuclear lines derived from erythrocyte nuclei of Rana pipiens were produced by serial nuclear transplantation into oocytes and eggs. Even at the termination of the experiments, embryos and tadpoles developed in the eighth transplant generations. Thus, there was no evidence that the mitotic progeny of the erythrocyte nuclei lost their ability to replicate their genomes and continue cell cycling. We conclude that the genome of noncycling and terminally differentiated erythrocytes maintains its potential for widespread replication and extensive reversal of gene function in excess of a hundred (centuplicate) cell cycles.
Subject(s)
DNA Replication , Erythrocytes/physiology , Oocytes/physiology , Rana pipiens/genetics , Animals , Blastocyst/ultrastructure , Gene Expression Regulation , Larva , Nuclear Transfer Techniques , Rana pipiens/blood , Rana pipiens/embryologyABSTRACT
In several experimental systems the genomic capacity in specialized cells can be assessed by examining the activation of dormant genes. Since some of these specialized cells can be induced to change cell phenotype, all cell specializations do not necessarily involve irreversible genetic changes.
Subject(s)
Cell Differentiation , Gene Expression Regulation , Animals , Anura , Cell Fusion , Cell Transformation, Neoplastic/metabolism , Chickens , Chromatin/physiology , DNA/genetics , DNA/metabolism , Drosophila , Embryo, Mammalian/physiology , Embryo, Nonmammalian , Extremities/growth & development , Humans , Hybrid Cells , Iris/growth & development , Methylation , Mice , Nuclear Transfer Techniques , Phenotype , Rats , XenopusABSTRACT
Adult erythrocyte nuclei of Rana, transplanted and incubated in the cytoplasm of maturing oocytes, direct matured oocytes to form swimming tadpoles. These results demonstrate that nuclei of noncycling and terminally differentiated erythrocytes contain the genes to specify tadpole development, and conditioning these nuclei in the cytoplasm of oocytes leads to a widespread reactivation of dormant genes.
Subject(s)
Erythrocytes/physiology , Gene Expression Regulation , Oocytes/physiology , Ovum/physiology , Animals , Cell Nucleus/physiology , Female , Nuclear Transfer Techniques , Rana pipiens/embryologySubject(s)
Adenocarcinoma/genetics , Embryo, Nonmammalian/cytology , Genes , Kidney Neoplasms/genetics , Nuclear Transfer Techniques , Adenocarcinoma/ultrastructure , Animals , Blastocyst/cytology , Cells, Cultured , Gastrula/cytology , Kidney Neoplasms/ultrastructure , Morphogenesis , Neoplasms, Experimental/genetics , Rana pipiensABSTRACT
Somatic nuclei, when transplanted into oocytes at the stage of first meiotic metaphase, were induced to undergo chromosome condensation and alignment on spindles. When the oocytes completed maturity in vitro and were activated, the somatic nuclei transformed into "fertilization" nuclei and promoted development through embryogenesis. Thus somatic nuclei can reversibly respond to cytoplasms directing either meiotic or mitotic events, and somatic nuclei from differentiated cells may be reversed by conditioning in oocytes.
