Aim: To identify differences between primed mouse embryonic stem cells (ESCs) and fully functional naive ESCs; to manipulate primed cells into a naive state.
Methods: We have cultured 3 lines of cells from different mouse strains that have been shown to be naive or primed as determined by generating germline-transmitting chimeras. Cells were put through a battery of tests to measure the different features. RNA from cells was analyzed using microarrays, to determine a priority list of the differentially expressed genes. These were later validated by quantificational real-time polymerase chain reaction. Viral cassettes were created to induce expression of differentially expressed genes in the primed cells through lentiviral transduction. Primed reprogrammed cells were subjected to in-vivo incorporation studies.
Results: Most results show that both primed and naive cells have similar features (morphology, proliferation rates, stem cell genes expressed). However, there were some genes that were differentially expressed in the naïve cells relative to the primed cells. Key upregulated genes in naïve cells include ESRRB, ERAS, ATRX, RNF17, KLF-5, and MYC. After over-expressing some of these genes the primed cells were able to incorporate into embryos in-vivo, re-acquiring a feature previously absent in these cells.
Conclusion: Although there are no notable phenotypic differences, there are key differences in gene expression between these naïve and primed stem cells. These differences can be overcome through overexpression.
Keywords: C-myc; ERAS; ESRRB; Induced stem cells; Overexpression.