Vikas Malik, Laura V. Glaser, Dennis Zimmer, Sergiy Velychko, Mingxi Weng et al.
Oct4, along with Sox2 and Klf4 (SK), can induce pluripotency but structurally similar factors like Oct6 cannot. To decode why Oct4 has this unique ability, we compare Oct4-binding, accessibility patterns and transcriptional waves with Oct6 and an Oct4 mutant defective in the dimerization with Sox2 (Oct4defSox2). We find that initial silencing of the somatic program proceeds indistinguishably with or without Oct4. Oct6 mitigates the mesenchymal-to-epithelial transition and derails reprogramming. These effects are a consequence of differences in genome-wide binding, as the early binding profile of Oct4defSox2 resembles Oct4, whilst Oct6 does not bind pluripotency enhancers. Nevertheless, in the Oct6-SK condition many otherwise Oct4-bound locations become accessible but chromatin opening is compromised when Oct4defSox2 occupies these sites. We find that Sox2 predominantly facilitates chromatin opening, whilst Oct4 serves an accessory role. Formation of Oct4/Sox2 heterodimers is essential for pluripotency establishment; however, reliance on Oct4/Sox2 heterodimers declines during pluripotency maintenance.
Vikas Malik, Laura V. Glaser, Dennis Zimmer, Sergiy Velychko, Mingxi Weng, Markus Holzner, Marius Arend, Yanpu Chen, Yogesh Srivastava, Veeramohan Veerapandian, Zahir Shah, Miguel A. Esteban, Huating Wang, Jiekai Chen, Hans R. Schöler, Andrew P. Hutchins, Sebastiaan H. Meijsing, Sebastian Pott, Ralf Jauch. Pluripotency reprogramming by competent and incompetent POU factors uncovers temporal dependency for Oct4 and Sox2. 2019-08-02. https://doi.org/10.1038/s41467-019-11054-7
An episomal STARR-reporter/qPCR assay tested two Oct4-bound mouse genomic regions near Sox21 and Spata13, each with a site-directed motif mutant, alongside a CMV positive control and three glucocorticoid-receptor negative controls. E14 mouse embryonic stem cells were transiently transfected with individual constructs, harvested after 24 hours, and GFP reporter expression was measured in four biological replicates.
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