C/EBP[alpha] creates elite cells for iPSC reprogramming by upregulating Klf4 and increasing the levels of Lsd1 and Brd4

Reprogramming somatic cells into induced pluripotent stem cells (iPSCs) is typically inefficient and has been explained by elite-cell and stochastic models. We recently reported that B cells exposed to a pulse of C/EBP alpha (B alpha' cells) behave as elite cells, in that they can be rapidly and efficiently reprogrammed into iPSCs by the Yamanaka factors OSKM. Here we show that C/EBP alpha post-transcriptionally increases the abundance of several hundred proteins, including Lsd1, Hdac1, Brd4, Med1 and Cdk9, components of chromatin-modifying complexes present at super-enhancers. Lsd1 was found to be required for B cell gene silencing and Brd4 for the activation of the pluripotency program. C/EBP alpha also promotes chromatin accessibility in pluripotent cells and upregulates Klf4 by binding to two haematopoietic enhancers. B alpha' cells share many properties with granulocyte/macrophage progenitors, naturally occurring elite cells that are obligate targets for leukaemic transformation, whose formation strictly requires C/EBP alpha.