Pluripotency of a polyploid H1 (ES) cell system without leukaemia inhibitory factor

Mouse embryonic stem cells maintain differentiation potency into somatic lineage despite alternation of ploidy

Vertebrates, including mammals, are considered to have evolved by whole genome duplications. Although some fish have been reported to be polyploids that have undergone additional genome duplication, there have been no reports of polyploid mammals due to abnormal development after implantation. Furthermore, as the number of physiologically existing tetraploid somatic cells is small, details of the functions of these ploidy-altered cells are not fully understood. In this present study, we aimed to clarify the details of the differentiation potency of tetraploids using tetraploid embryonic stem cells. To clarify the differentiation potency, we used mouse tetraploid embryonic stem cells derived from tetraploid embryos. We presented tetraploid embryonic stem cells differentiated into neural and osteocyte lineage in vitro and tetraploid cells that contributed to various tissues of chimeric embryos ubiquitously in vivo. These results revealed that mouse embryonic stem cells maintain differentiation potency after altering the ploidy. Our results provide an important basis for the differentiation dynamics of germ layers in mammalian polyploid embryogenesis.

Analysis of centromere signal patterns in breast cancer cells with chromosomal instability using image cytometry combined with centromere fluorescence in situ hybridization

Fluorescence in situ hybridization (FISH) with centromeric probes is a method used to detect chromosomal instability (CIN), a hallmark of most cancers. However, no studies thus far have investigated the relationship between centromeric FISH signals and the cell cycle in cancer cells. In this study, the chromosome content in each cell cycle phase was evaluated with respect to the number of centromeric FISH signals in two breast cancer cell lines and eight surgically resected breast cancer specimens using image cytometry. Variations in chromosome number were detected at each phase of the cell cycle but were not associated with proliferative capacity in the cell lines. Furthermore, the chromosome doubling frequency differed in each cell line and clinical specimen. These results reveal two aspects of centromeric FISH signal variation in breast cancers that exhibit CIN, and suggest that chromosome doubling is a remarkable occurrence that may increase the heterogeneity of tumors.

Dodecaploid H1 embryonic stem cells abolished pluripotency in L15F10 medium both with and without leukemia inhibitory factor

Two lines of dodecaploid H1 embryonic stem cells, 12H1 and 12H1(-) cells (mouse-originated cells), were established through polyploidization of two hexaploid H1 cells, 6H1 and 6H1(-) cells, which were cultured in L15F10 (7:3) medium with and without leukemia inhibitory factor (LIF), respectively. The G1, S, and G2/M phase fractions of 12H1 and 12H1(-) cells were almost the same as those of 6H1 and 6H1(-) cells, respectively, but the doubling time of cell proliferation was prolonged, suggesting that cell death occurred in 12H1 and 12H1(-)cells. The cell volumes of 12H1 and 12H1(-) cells were about double those of 6H1 and 6H1(-) cells, respectively. 12H1 and 12H1(-) cells showed near-negative activity of alkaline phosphatase and no ability to form teratocarcinomas in mouse abdomen, suggesting that 12H1 and 12H1(-) cells lost pluripotency. The DNA contents of 12H1 and 12H1(-) cells decayed in long-term culturing, suggesting that 12H1 and 12H1(-) cells were DNA-unstable. Possible explanations for the lost pluripotency and for the DNA decay in 12H1 and 12H1(-) cells are presented.