title: Differentiation of human embryonic stem cells induces condensation of chromosome territories and formation of heterochromatin protein 1 foci.
abstract: Human embryonic stem cells (hES) are unique in their pluripotency and capacity for self-renewal. Therefore, we have studied the differences in the level of chromatin condensation in pluripotent and all-trans retinoic acid-differentiated hES cells. Nuclear patterns of the Oct4 (6p21.33) gene, responsible for hES cell pluripotency, the C-myc (8q24.21) gene, which controls cell cycle progression, and HP1 protein (heterochromatin protein 1) were investigated in these cells. Unlike differentiated hES cells, pluripotent hES cell populations were characterized by a high level of decondensation for the territories of both chromosomes 6 (HSA6) and 8 (HSA8). The Oct4 genes were located on greatly extended chromatin loops in pluripotent hES cell nuclei, outside their respective chromosome territories. However, this phenomenon was not observed for the Oct4 gene in differentiated hES cells, for the C-myc gene in the cell types studied. The high level of chromatin decondensation in hES cells also influenced the nuclear distribution of all the variants of HP1 protein, particularly HP1 alpha, which did not form distinct foci, as usually observed in most other cell types. Our experiments showed that unlike C-myc, the Oct4 gene and HP1 proteins undergo a high level of decondensation in hES cells. Therefore, these structures seem to be primarily responsible for hES cell pluripotency due to their accessibility to regulatory molecules. Differentiated hES cells were characterized by a significantly different nuclear arrangement of the structures studied.
authors.affiliation: Laboratory of Molecular Cytology, Cytometry Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 612 65, Brno, Czech Republic.
authors.forename: Eva
authors.initials: E
authors.lastname: Bártová
authors.forename: Jana
authors.initials: J
authors.lastname: Krejcí
authors.forename: Andrea
authors.initials: A
authors.lastname: Harnicarová
authors.forename: Stanislav
authors.initials: S
authors.lastname: Kozubek
mesh_terms: D001665:Binding Sites / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics*; D002460:Cell Line; D002467:Cell Nucleus / Q000235:genetics / Q000648:ultrastructure; D042002:Chromatin Assembly and Disassembly; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D053595:Embryonic Stem Cells / Q000378:metabolism / Q000648:ultrastructure*; D006801:Humans; D039904:Pluripotent Stem Cells / Q000378:metabolism / Q000648:ultrastructure*; D015398:Signal Transduction / Q000235:genetics; D015534:Trans-Activators / Q000187:drug effects / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D015534:Trans-Activators; D000090266:Chromobox Protein Homolog 5; D014212:Tretinoin