Conclusions
Our study identifies previously unrecognized heterogeneity due to KLF3 protein expression in mESCs.
Methods
Klf3 mRNA and protein were analysed by RT-qPCR, Western blotting or immunofluorescence in mESCs, C2C12 cells, early mouse embryos and various mouse tissues. An ESC reporter line expressing KLF3-GFP fusion protein was made to study heterogeneity of KLF3 protein expression in ESCs. GFP-positive mESCs were sorted for further analysis including RT-qPCR and RNA-seq.
Results
In the majority of mESCs, KLF3 protein is actively degraded due to its proline-rich sequence and highly disordered structure. Interestingly, KLF3 protein is stabilized in a small subset of mESCs. Transcriptome analysis indicates that KLF3-positive mESCs upregulate genes that are initially activated in 8-cell embryos. Consistently, KLF3 protein but not mRNA is dramatically increased in 8-cell embryos. Forced expression of KLF3 protein in mESCs promotes the expression of 8-cell-embryo activated genes. Conclusions: Our study identifies previously unrecognized heterogeneity due to KLF3 protein expression in mESCs.