Reprogramming Factor Stoichiometry Influences the Epigenetic State and Biological Properties of Induced Pluripotent Stem Cells

SummaryWe compared two genetically highly defined transgenic systems to identify parameters affecting reprogramming of somatic cells to a pluripotent state. Our results demonstrate that the level and stoichiometry of reprogramming factors during the reprogramming process strongly influence the resulting pluripotency of iPS cells. High expression of Oct4 and Klf4 combined with lower expression of c-Myc and Sox2 produced iPS cells that efficiently generated “all-iPSC mice” by tetraploid (4n) complementation, maintained normal imprinting at the Dlk1-Dio3 locus, and did not create mice with tumors. Loss of imprinting (LOI) at the Dlk1-Dio3 locus did not strictly correlate with reduced pluripotency though the efficiency of generating “all-iPSC mice” was diminished. Our data indicate that stoichiometry of reprogramming factors can influence epigenetic and biological properties of iPS cells. This concept complicates efforts to define a “generic” epigenetic state of iPSCs and ESCs and should be considered when comparing different iPS and ES cell lines.

Graphical AbstractFigure optionsDownload full-size imageDownload high-quality image (201 K)Download as PowerPoint slideHighlights► Optimal reprogramming factor stoichiometry yields high-quality iPSCs ► Infrequent loss of imprinting (LOI) of Dlk1-Dio3 iPSCs seen in Col1a-OSKM mice ► Adult mice from Col1a1-OSKM iPSCs do not develop tumors ► Dlk1-Dio3 LOI is not an absolute marker for reduced pluripotency