Molecular insights into somatic cell reprogramming to induced pluripotent stem cells (iPS) would aid regenerative medicine, but are difficult to elucidate in iPS because of their heterogeneity, as relatively few cells undergo reprogramming (0.1–1%; refs 1, 2). To identify early acting regulators, we capitalized on non-dividing heterokaryons (mouse embryonic stem cells fused to human fibroblasts), in which reprogramming towards pluripotency is efficient and rapid3, enabling the identification of transient regulators required at the onset. We used bi-species transcriptome-wide RNA-seq to quantify transcriptional changes in the human somatic nucleus during reprogramming towards pluripotency in heterokaryons. During heterokaryon reprogramming, the cytokine interleukin 6 (IL6), which is not detectable at significant levels in embryonic stem cells, was induced 50-fold. A 4-day culture with IL6 at the onset of iPS reprogramming replaced stably transduced oncogenic c-Myc such that transduction of only Oct4, Klf4 and Sox2 was required. IL6 also activated another Jak/Stat target, the serine/threonine kinase gene Pim1, which accounted for the IL6-mediated twofold increase in iPS frequency. In contrast, LIF, another induced GP130 ligand, failed to increase iPS frequency or activate c-Myc or Pim1, thereby revealing a differential role for the two Jak/Stat inducers in iPS generation. These findings demonstrate the power of heterokaryon bi-species global RNA-seq to identify early acting regulators of reprogramming, for example, extrinsic replacements for stably transduced transcription factors such as the potent oncogene c-Myc.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $18.75 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Gene Expression Omnibus
We thank M. Wernig and S. Marro for providing expert guidance with iPS protocols and for the STEMCAA 4F lentiviral construct and R. Tran-Bussat for isolating MEFs. We thank S. L. Oliver, S. Corbel and D. Burns for their insightful comments on the manuscript, the ENCODE Project, in particular Barbara Wold who was very helpful in the initiation of this work, and the Stanford FACS Facility, PAN Facility, and Stem Cell Institute Genome Facility. This work was supported by NSF and Bio-X Graduate Research Fellowships to J.J.B., by NIH grant R01 HG005717 and HG006018 to W.H.W., and by CIRM grant RB1-01292, NIH U01 HL100397, NIH R01 AG009521 and the Baxter Foundation to H.M.B.
Integrated supplementary information
About this article
Frontiers in Pharmacology (2019)