Globin synthesis in hybrid cells constructed by transplantation of dormant avian erythrocyte nuclei into enucleated fibroblasts

Somatic cells, stem cells, and induced pluripotent stem cells: how do they now contribute to conservation?

More than a decade has now passed since the birth of the first endangered species produced from an adult somatic cell reprogrammed by somatic cell nuclear transfer. At that time, advances made in domestic and laboratory animal species provided the necessary foundation for attempting cutting-edge technologies on threatened and endangered species. In addition to nuclear transfer, spermatogonial stem cell transplantation and induction of pluripotent stem cells have also been explored. Although many basic scientific questions have been answered and more than 30 wild species have been investigated, very few successes have been reported. The majority of studies document numerous obstacles that still need to be overcome to produce viable gametes or embryos for healthy offspring production. This chapter provides an overview of somatic cell and stem cell technologies in different taxa (mammals, fishes, birds, reptiles and amphibians) and evaluates the potential and impact of these approaches for animal species conservation.

Nuclear envelope removal/maintenance determines the structural and functional remodelling of embryonic red blood cell nuclei in activated mouse oocytes

Nuclei of embryonic red blood cells (e-RBC) from 12-day mouse fetuses are arrested in G0 phase of the cell cycle and have low transcriptional activity. These nuclei were transferred with help of polyethylene glycol (PEG)-mediated fusion to parthenogenetically activated mouse oocytes and heterokaryons were analysed for nuclear structure and transcriptional activity. If fusion proceeded 25-45 min after oocyte activation, e-RBC nuclei were induced to nuclear envelope breakdown and partial chromatin condensation, followed by formation of nuclei structurally identical with pronuclei. These 'pronuclei', similar to egg (female) pronuclei, remained transcriptionally silent over several hours of in vitro culture. If fusion was performed 1 h or later (up to 7 h) after activation, the nuclear envelope of e-RBC nuclei remained intact and nuclear remodelling was less spectacular (slight chromatin decondensation, formation of nucleolus precursor bodies). These nuclei, however, reinforced polymerase-II-dependent transcription within a few hours of in vitro culture. Our present experiments, together with our previous work, demonstrate that nuclear envelope breakdown/maintenance are critical events for nuclear remodelling in activated mouse oocytes and that somatic dormant nuclei can be stimulated to renew transcription at a time when the female pronucleus remains transcriptionally silent.

Differences in erythropoiesis in normal chicken and quail embryos

Using antibodies against the fetal and adult forms of alpha- and beta-globin, it has been shown that erythropoiesis in the para-aortic foci (PAF) constitutes a major species-specific difference between chicken and quail embryos. In quail embryos, para-aortic foci are rare, small and rather heterogeneous with regard to their erythropoietic and haemopoietic cell composition. In contrast, the PAFs in chicken embryos are abundant and consist of large numbers of erythropoietic cells. In both species a time difference (approximately 1 day) is observed between the first expression of the fetal alpha- and beta-globin and the adult alpha- and beta-globin in erythropoietic cells. Adult erythropoiesis in both species can be detected first in the stalk of the yolk sac; this is similar to the situation in mammalian and amphibian species. From this time onward the number of circulating adult erythrocytes increases steadily. Whereas in chicken, large intraembryonic foci that can serve as sources for these adult cells arise concomitantly, no such foci can be detected in quail embryos, suggesting that the quail yolk sac is a major source for these adult red blood cells.

Cell differentiation features in embryos resulting from interphylum nuclear transplantation: echinoderm nucleus to ascidian zygote cytoplasm

When an echinoderm nucleus was transplanted into an ascidian zygote cytoplast there was developmental cooperation at the cellular level between nucleus and cytoplasm of these normally nonhybridizable species. A blastula stage nucleus from the sand dollar Echinarachnius parma was injected into an activated but nonnucleate egg fragment of the ascidian Ciona intestinalis. During culture, some of the "hybrid" embryos displayed ultrastructural evidence of cellular differentiation. Two recognizable features were (1) extracellular matrix components, and (2) neural cell characteristics, including elaboration of associated cilia. Nonnucleate zygote fragments alone, and such fragments injected with seawater or punctured by glass needle, did not develop organized subcellular structures. Morphologic expressions resulting from nuclear transplantations between these two phyla (Echinodermata and Chordata) seemingly indicate functional interactions at a gene regulatory level. Creation of such nuclear-cytoplasmic hybrids suggests thereby a means of exploring the nature of the egg cytoplasmic agents in ascidian embryos that appear to determine gene expression related to histospecific differentiation products.

Protein synthesis in differentiating normal and leukemic erythroid cells

Erythroleukemic cells transformed by the AEV or S13 strains of avian erythroblastosis virus differentiate in vitro either spontaneously (S13) or following a temperature induction (temperature-sensitive mutants of AEV). To study differentiation in these cells at the molecular level, homogeneous fractions of maturing cells at discrete stages of differentiation were prepared by Percoll density-gradient centrifugation. This method was also used for the fractionation of differentiating normal erythroid cells separated from total bone marrow by an immunological "panning" technique. Total protein synthesis in these cells was then analyzed by two-dimensional gel electrophoresis. The expression of several proteins was altered in differentiating leukemic cells but not in their normal counterparts. However, in general, the normal and leukemic cells from comparable stages of maturity showed closely related protein synthetic patterns. Similar early and late changes in the synthesis of a number of polypeptides were detected during maturation from early erythroid precursors to terminally differentiated erythrocytes. Further, the leukemic as well as the normal cells appeared to undergo a major switch in total protein synthetic pattern during late differentiation. These results demonstrate that normal and erythroleukemic cells differentiate along similar pathways.

Status of the nuclear matrix in mature and embryonic chick erythrocyte nuclei

The adult chicken erythrocyte nucleus was found to lack an internal nuclear matrix: even milder extraction procedures resulted in the production of empty shells of pore complex-lamina together with loose aggregates of core histone. In contrast, rat liver nuclei showed a typical intranuclear salt-resistant skeleton. These results show that an internal matrix is not an obligatory nuclear component, and is not required for the spatial organization of chromatin. 5-day-old embryonic erythrocytes did, however, contain an interchromatinic nuclear matrix, suggesting a correlation between the presence of matrix structures, and nuclear 'activity'.