Whole-genome chromosome distribution during nuclear fragmentation of giant trophoblast cells of Microtus rossiaemeridionalis studied with the use of gonosomal chromatin arrangement

Abstract

Gonosomal chromatin bodies (GCBs), i.e. blocks of condensed chromatin consisting of heterochromatized region of the sex chromosomes of the field vole M. rossiaemeridionalis, were used as a natural interphase chromosome marker in order to clarify the regularities of GCB rearrangement during nuclear fragmentation of secondary giant trophoblast cells (SGTCs) at the end of their differentiation. Cytophotometrical measurements of DNA content in the nuclei, nuclear fragments and simultaneously in the GCBs were made in the secondary giant SGTCs of field vole M. rossiaemeridionalis. In most cases 1 to 2 GCBs get into the nuclear fragments at different ploidy levels. In the nuclear fragments, GCB DNA content decreased mostly proportionally to DNA content in the whole fragments corresponding to 2c, 4c and 8c. The data obtained demonstrate a regular whole-genome chromosome distribution into nuclear fragments. A possible mechanism of nuclear fragmentation that largely ensures a balanced genome in nuclear fragments is discussed.

Activation of Meiosis-Specific Genes Is Associated with Depolyploidization of Human Tumor Cells following Radiation-Induced Mitotic Catastrophe

“…These earlier studies have raised questions as to the fate of polyploid tumor cells produced during anti-cancer treatment, the ability of these cells to undergo depolyploidization, and the role of these processes in tumor progression. That normal mammalian cells are able to undergo depolyploidization was reported by Zybina and Zybina in 2005 (11) who showed that whole genome segregation occurs in the giant nuclei (more than 100N) of the trophoblasts (the cells that form the outer layer of the blastocyst and mediate the implantation of the embryo into the endometrium) originating cells containing 2N, 4N and 8N chromosome complements. These results suggest that depolyploidization might be a common phenomenon and that cells may possess an internal control for segregation of entire genomes.…”

Multinucleated giant cells from fibroblast cultures

“…Both multinucleation and polyploidy (nuclear replication without nuclear division) have been seen in senescent fibroblasts [18, 19]. Multinucleation and polyploidy are also well-known in trophoblasts [46, 47] and cancerous tissue [20, 43]. Though senescence has been proposed as a mechanism to prevent cells from oncogenesis [48], the nuclear material in senescent multinucleate fibroblasts is considered highly unstable, and on occasion cells can escape senescence by a nuclear budding process known as neosis [20, 21, 49].…”

Genome reversion process of endopolyploidy confers chromosome instability on the descendent diploid cells

“…This idea stems from the fact that the peculiar ‘endo‐divison’ sequence is genetic‐based with its complete occurrence (mitotic—meiosis) in vegetative/sexual reproduction of the primitive unicellular radiolarian, Aulachanta (Grell and Ruthmann, 1964; Hunding, 1981; Raikov, 1982, 1994). Its evolutionary preservation in mammalian cells is supported by co‐segregation of whole complements in the absence of normal spindle activity in a rodent trophoblasts (Zybina et al, 2005), and from nuclear fragmentation (endomitosis) of high endopolyploidy (>8 n ) into genome‐reduced euploid products with mitotic capacity (Walen, 2010). In short, the hypothesis is that inheritance of ‘endo‐division traits’ (e.g.…”