Differentiation of Human Pluripotent Stem Cells into Mesodermal and Ectodermal Derivatives Is Independent of the Type of Isogenic Reprogrammed Somatic Cells.

Induced pluripotent stem cells (iPSCs) have the capacity to unlimitedly proliferate and differentiate into all types of somatic cells. This capacity makes them a valuable source of cells for research and clinical use. However, the type of cells to be reprogrammed, the selection of clones, and the various genetic manipulations during reprogramming may have an impact both on the properties of iPSCs and their differentiated derivatives. To assess this influence, we used isogenic lines of iPSCs obtained by reprogramming of three types of somatic cells differentiated from human embryonic stem cells. We showed that technical manipulations in vitro, such as cell sorting and selection of clones, did not lead to the bottleneck effect, and that isogenic iPSCs derived from different types of somatic cells did not differ in their ability to differentiate into the hematopoietic and neural directions. Thus, the type of somatic cells used for the generation of fully reprogrammed iPSCs is not important for the practical and scientific application of iPSCs.

[Genetic Cell Reprogramming: A New Technology for Basic Research and Applied Usage].

Gene function disclosure and the development of modern technologies of genetic manipulations offered the possibility of genetic reprogramming application to alter cell specialization. With the involvement of a gene set that encodes the transcription factors responsible for the pluripotent state, any cell of an adult body could be reprogrammed into the embryonal.state and pluripotency could be induced in this cell. Such reprogrammed cells were called induced pluripotent stem cells (iPSCs), and they are capable of again passing through all developmental stages. This provides new possibilities for studies of the basic mechanisms of developmental biology, the formation of specific cell types, and the whole body. In culture, iPSCs could be maintained permanently in a nontransformed state and permit genetic manipulations while maintaining their pluripotent properties. Such a unique combination of their properties makes them an attractive tool for studies of various pathologies and for the delineation of treatment approaches. This review discusses the basic and applied aspects of iPSCs biology.

In embryonic chicken erythrocytes actively transcribed alpha globin genes are not associated with the nuclear matrix.

The spatial organization of a 250 Kb region of chicken chromosome 14, which includes the alpha globin gene cluster, was studied using in situ hybridization of a corresponding BAC probe with nuclear halos. It was found that in non-erythroid cells (DT40) and cultured erythroid cells of definite lineage (HD3) the genomic region under study was partially (DT40 cells) or fully (HD3 cells) associated with the nuclear matrix. In contrast, in embryonic red blood cells (10-day RBC) the same area was located in the crown of DNA loops surrounding the nuclear matrix, although both globin genes and surrounding house-keeping genes were actively transcribed in these cells. This spatial organization was associated with the virtual absence of RNA polymerase II in nuclear matrices prepared from 10-day RBC. In contrast, in HD3 cells a significant portion of RNA polymerase II was present in nuclear matrices. Taken together, these observations suggest that in embryonic erythroid cells transcription does not occur in association with the nuclear matrix.

The organization in micro-loops of an extended fragment of chicken chromosome 14, including the alpha globin gene cluster in the erythroid cells.

It has been shown that the activation of tissue-specific gene transcription during the course of cell differentiation is associated with a spatial reorganization of the genomic domains harboring those specific genes. This reorganization consists of the relocation to the nuclear matrix of the whole genomic domain containing one or more of the genes being transcribed. However, it remains unclear whether, during this process, extended areas of the genome also become attached to the nuclear matrix. We studied the genome´s pattern of interaction with the nuclear matrix in both erythroid and non-erythroid cells of chickens, using a 220Kb region of chromosome #14, which contains the alpha-globin gene cluster and some surrounding house-keeping genes. The results show that in erythroid cells, the fragment of the genome containing the alpha-globin gene domain became spatially arranged into micro-loops which could not be detected by mapping experiments.