Self-renewal of human embryonic stem cells is supported by a shortened G1 cell cycle phase
Biochemistry & Molecular Pharmacology
Graduate School of Biomedical Sciences; Department of Cell Biology
Medical Subject Headings
Animals; Biological Markers; Cell Differentiation; Cell Line; *Cell Proliferation; Cyclin-Dependent Kinase 4; Cyclins; Embryonic Stem Cells; G1 Phase; Humans; Karyotyping; RNA, Messenger; Time Factors
Life Sciences | Medicine and Health Sciences
Competency for self-renewal of human embryonic stem (ES) cells is linked to pluripotency. However, there is a critical paucity of fundamental parameters of human ES cell division. In this study we show that human ES cells (H1 and H9; NIH-designated WA01 and WA09) rapidly proliferate due to a very short overall cell cycle (15-16 h) compared to somatic cells (e.g., normal diploid IMR90 fibroblasts and NT-2 teratocarcinoma cells). The human ES cell cycle maintains the four canonical cell cycle stages G1, S, G2, and M, but the duration of G1 is dramatically shortened. Bromodeoxyuridine (BrdU) incorporation and FACS analysis demonstrated that 65% of asynchronously growing human ES cells are in S phase. Immunofluorescence microscopy studies detecting BrdU labeled mitotic chromosomes, Ki67 domains, and p220(NPAT) containing Cajal bodies revealed that the durations of the S ( approximately 8 h), G2 ( approximately 4 h), and M phases ( approximately 1 h) are similar in ES and somatic cells. We determined that human ES cells remain viable after synchronization with either nocodazole or the anti-tumor drug Paclitaxel (taxol) and have an abbreviated G1 phase of only 2.5-3 h that is significantly shorter than in somatic cells. Molecular analyses using quantitative RT-PCR demonstrate that human ES cells and somatic cells express similar cell cycle markers. However, among cyclins and cyclin-dependent kinases (CDKs), we observed high mRNA levels for the G1-related CDK4 and cyclin D2 genes. We conclude that human ES cells exhibit unique G1 cell cycle kinetics and use CDK4/cyclin D2 related mechanisms to attain competency for DNA replication.
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Citation: J Cell Physiol. 2006 Dec;209(3):883-93. Link to article on publisher's site
Becker, Klaus A.; Ghule, Prachi N.; Therrien, Jaclyn A.; Lian, Jane B.; Stein, Janet L.; Van Wijnen, Andre J.; and Stein, Gary S., "Self-renewal of human embryonic stem cells is supported by a shortened G1 cell cycle phase" (2006). GSBS Student Publications. 91.