Retinoblastoma-binding proteins 4 and 9 are important for human pluripotent stem cell maintenance.
OBJECTIVE: The molecular mechanisms that maintain human pluripotent stem (PS) cells are not completely understood. Here we sought to identify new candidate PS cell regulators to facilitate future improvements in their generation, expansion, and differentiation. MATERIALS AND METHODS: We used bioinformatic analyses of multiple serial-analysis-of-gene-expression libraries (generated from human PS cells and their differentiated derivatives), together with small interfering RNA (siRNA) screening to identify candidate pluripotency regulators. Validation of candidate regulators involved promoter analyses, Affymetrix profiling, real-time PCR, and immunoprecipitation. RESULTS: Promoter analysis of genes differentially expressed across multiple serial-analysis-of-gene-expression libraries identified E2F motifs in the promoters of many PS cell-specific genes (e.g., POU5F1, NANOG, SOX2, FOXD3). siRNA analyses identified two retinoblastoma binding proteins (RBBP4, RBBP9) as required for maintenance of multiple human PS cell types. Both RBBPs were bound to RB in human PS cells, and E2F motifs were present in the promoters of genes whose expression was altered by decreasing RBBP4 and RBBP9 expression. Affymetrix and real-time PCR studies of siRNA-treated human PS cells showed that reduced RBBP4 or RBBP9 expression concomitantly decreased expression of POU5F1, NANOG, SOX2, and/or FOXD3 plus certain cell cycle genes (e.g., CCNA2, CCNB1), while increasing expression of genes involved in organogenesis (particularly neurogenesis). CONCLUSIONS: These results reveal new candidate positive regulators of human PS cells, providing evidence of their ability to regulate expression of pluripotency, cell cycle, and differentiation genes in human PS cells. These data provide valuable new leads for further elucidating mechanisms of human pluripotency.
DMEM/F-12 with 15 mM HEPES
Dulbecco's Phosphate Buffered Saline with 2% Fetal Bovine Serum
Human Recombinant bFGF
Venu P et al. (APR 2010)
In vitro cellular & developmental biology. Animal 46 3-4 200--5
Analysis of long-term culture properties and pluripotent character of two sibling human embryonic stem cell lines derived from discarded embryos
We had earlier reported the derivation and characterization of two new sibling human embryonic stem cell lines BJNhem19 and BJNhem20, from discarded grade III embryos of Indian origin. We report here the characteristics of the two sibling cell lines after long-term continuous culture for over 2 yr during which they have been passaged over 200 times. We show that both cell lines adapt well to culture on various mouse and human feeders as well as in feeder-free conditions. The cells show normal diploid karyotype and continue to express all pluripotency markers. Both cell lines differentiate to derivatives of all three germ layers in vitro. However as reported earlier, BJNhem19 is unable to generate teratomas in nude or SCID mice or differentiate to beating cardiomyocytes when tested over several passages during long-term stable culture. On the other hand, the cardiac differentiation capacity of BJNhem20 is greatly increased, and it can generate beating cardiomyocytes that proliferate when isolated and cultured further. In conclusion, the two cell lines have maintained a stable phenotype for over 2 yr and are indeed immortal. Their derivation from grade III embryos does not seem to have any adverse effect on their long-term phenotype. The cells can be obtained for research purposes from the UK Stem Cell Bank and from the authors.