Cyclin A₁ Is Essential for Setting the Pluripotent State and Reducing Tumorigenicity of Induced Pluripotent Stem Cells

Abstract

The proper differentiation and threat of cancer rising from the application of induced pluripotent stem (iPS) cells are major bottlenecks in the field and are thought to be inherently linked to the pluripotent nature of iPS cells. To address this question, we have compared iPS cells to embryonic stem cells (ESCs), the gold standard of ground state pluripotency, in search for proteins that may improve pluripotency of iPS cells. We have found that when reprogramming somatic cells toward pluripotency, 1%-5% of proteins of 5 important cell functions are not set to the correct expression levels compared to ESCs, including mainly cell cycle proteins. We have shown that resetting cyclin A 1 protein expression of early-passage iPS cells closer to the ground state pluripotent state of mouse ESCs improves the pluripotency and reduces the threat of cancer of iPS cells. This work is a proof of principle that reveals that setting expression of certain proteins correctly during reprogramming is essential for achieving ESC-state pluripotency. This finding would be of immediate help to those researchers in different fields of iPS cell work that specializes in cell cycle, apoptosis, cell adhesion, cell signaling, and cytoskeleton.

Runx2 Regulates Endochondral Ossification Through Control of Chondrocyte Proliferation and Differentiation

“…Cyclin A1‐deficient mice show no skeletal phenotype, but cyclin A2 null mice die in utero long before the initiation of skeletogenesis . Interestingly, cyclin A1 reduction in conjuction with c‐Myb is associated with decreased proliferation and maintenance of pluripotency of iPS cells . Thus, proliferative defects in Runx2 null chondrocytes reflect combined changes in multiple cell cycle regulatory genes.…”

Crosstalk between stem cell and cell cycle machineries

“…However, the effects of Rb loss on reprogramming involves a direct repression of the core pluripotency network, rather than perturbations of the cell cycle, indicating that at least this critical tumor suppressor may possess separate functions to both regulate proliferation and pluripotency [37]. Along with CDK regulation, modulating the proper levels of CDK partner Cyclins is fundamental to proper reprogramming [59,60]. As in ES cells, Myc activity increases the rate of proliferation and reprogramming by helping to establish a pluripotent cell cycle in reprogrammed cells [10–12,61].…”

Plant Hormones Increase Efficiency of Reprogramming Mouse Somatic Cells to Induced Pluripotent Stem Cells and Reduce Tumorigenicity

“…The generation of iPS cells using mouse embryonic fibroblasts (MEFs) from C57BL/6 mice has been previously described [17]. MEFs were engineered to express an Oct4-promoter-driven GFP tag (Oct4-GFP MEFs) and used at passage 1 to 3 for the reprogramming experiments.…”

“…The use of previously characterized and established mouse iPS cells using MEFs from C57BL/6 mice has been previously described [17]. Mouse iPS cells were maintained in G4 media, which was changed every day.…”