Project description:Embryonic stem (ES) cells are isolated from the inner cell mass (ICM) of developing blastocysts, whereas epiblast stem cells (EpiSCs) are derived from the post-implantation epiblast and are characterized by a restricted developmental potential. Although certain mouse strains, such as the non-obese diabetic (NOD) mice, are considered “non-permissive” for ES cell derivation, they retain the capacity to generate EpiSCs. Using the NOD strain as a model, we characterized the stability of pluripotent states in cells generated by ICM explantation or direct in vitro reprogramming. We find that ES-like NOD stem cells can be captured in both approaches by providing exogenous constitutive expression of Klf4 or c-Myc transcription factors or small molecules that can replace these factors during in vitro reprogramming. The fully pluripotent NOD ES and iPS cells appear “metastable”, as the cells acquire an alternative EpiSC-like identity after removal of the exogenous factors, while reintroduction of these factors converts the cells back to ICM-like pluripotency. Our findings suggest that stem cells from different genetic backgrounds can assume distinct states of pluripotency in vitro, the stability of which is regulated by endogenous genetic determinants and can be modified by the continuous presence of defined exogenous factors. Gene expression profiling was performed in mouse ES, EpiSC and EpiSC-like cell lines.
Project description:Embryonic stem (ES) cells are isolated from the inner cell mass (ICM) of developing blastocysts, whereas epiblast stem cells (EpiSCs) are derived from the post-implantation epiblast and are characterized by a restricted developmental potential. Although certain mouse strains, such as the non-obese diabetic (NOD) mice, are considered “non-permissive” for ES cell derivation, they retain the capacity to generate EpiSCs. Using the NOD strain as a model, we characterized the stability of pluripotent states in cells generated by ICM explantation or direct in vitro reprogramming. We find that ES-like NOD stem cells can be captured in both approaches by providing exogenous constitutive expression of Klf4 or c-Myc transcription factors or small molecules that can replace these factors during in vitro reprogramming. The fully pluripotent NOD ES and iPS cells appear “metastable”, as the cells acquire an alternative EpiSC-like identity after removal of the exogenous factors, while reintroduction of these factors converts the cells back to ICM-like pluripotency. Our findings suggest that stem cells from different genetic backgrounds can assume distinct states of pluripotency in vitro, the stability of which is regulated by endogenous genetic determinants and can be modified by the continuous presence of defined exogenous factors.
Project description:Pluripotent stem cells provide a platform to interrogate control elements that function to generate all cell types of the body. Despite their utility for modeling development and disease, the relationship of mouse and human pluripotent stem cell states to one another remains largely undefined. We have shown that mouse embryonic stem (ES) cells and epiblast stem cells (EpiSCs) are distinct, pluripotent states isolated from pre- and post-implantation embryos respectively. Human ES cells are different than mouse ES cells and share defining features with EpiSCs, yet are derived from pre-implantation human embryos. Here we show that EpiSCs can be routinely derived from pre-implantation mouse embryos. The pre-implantation-derived EpiSCs exhibit molecular features and functional properties consistent with bona fide EpiSCs. These results provide a simple method for isolating EpiSCs and offer direct insight into the intrinsic and extrinsic mechanisms that regulate the acquisition of distinct pluripotent states. 6 total samples were analyzed. Three pluripotent cell types (mES cells, E3.5 EpiSCs, and E5.5 EpiSCs) were compared with and without treatment of SB431542 for 4 days.
Project description:Pluripotent stem cells provide a platform to interrogate control elements that function to generate all cell types of the body. Despite their utility for modeling development and disease, the relationship of mouse and human pluripotent stem cell states to one another remains largely undefined. We have shown that mouse embryonic stem (ES) cells and epiblast stem cells (EpiSCs) are distinct, pluripotent states isolated from pre- and post-implantation embryos respectively. Human ES cells are different than mouse ES cells and share defining features with EpiSCs, yet are derived from pre-implantation human embryos. Here we show that EpiSCs can be routinely derived from pre-implantation mouse embryos. The pre-implantation-derived EpiSCs exhibit molecular features and functional properties consistent with bona fide EpiSCs. These results provide a simple method for isolating EpiSCs and offer direct insight into the intrinsic and extrinsic mechanisms that regulate the acquisition of distinct pluripotent states.
Project description:Specification to primordial germ cells (PGCs) occurs under the mesoderm induction signals during gastrulation. Here, we found that Akt activation in embryonic stem (ES) cells generated self-renewing spheres during mesodermal differentiation induction and that the differentiation status of the sphere cells was in between ES cells and PGCs. Essential regulators for PGC specification and their downstream germ cell-specific genes were expressed in the spheres, showing that the cells of the sphere commenced the differentiation to germ lineage. However, the spheres could not proceed to spermatogenesis after transplantation to testes. Meanwhile, the transfer of the spheres to the original feeder-free ES cell culture conditions induced chaotic differentiation. In contrast, when the spheres were cultured on mouse embryonic fibroblasts or in the presence of ERK-cascade and GSK3 inhibitors, the reversion to the ES cell-like cell states was induced. These results indicate that the Akt signaling brings about a novel metastable and pluripotent state between ES cells and PGCs. Five samples were analyzed, which included the Akt-Mer-expressing ES cell (ESC) line #21 treated with or without 4OHT (4-hydroxytamoxifen), the #21 ESC-derived primordial germ cell (PGC)-like sphere cells and the ESC-like cells reverted from #21 PGC-like sphere cells. The PGC-like sphere cells derived from another Akt-Mer ESC line #42 was also examined.
Project description:Heterogeneity in pluripotent cells marks a metastable state where cells may drift between native and lineage-primed populations. While the role for these heterogeneities are unclear, they may reflect the dynamic equilibriums of signaling networks and have a direct effect on differentiation potentialities. Here, we report the role of the cell cycle in establishing heterogeneity of human pluripotent stem cells. By utilizing the FUCCI cell cycle indicator system coupled to fluorescent activated cell sorting (FACS), we have uncovered that the cell cycle drives heterogeneity at the epigenetic, transcriptional and post-transcriptional levels. Our data show widespread dynamics in 5-hydroxymethylcytosine (5hmC) during the cell cycle. Furthermore, transcript profiling by RNA-sequencing identified >500 genes that were cell cycle-regulated, of which the largest cohort of genes were transcriptional regulators. In sum, we demonstrate the role of the cell cycle in coordinating cellular transitions between metastable states in pluripotent stem cells. mRNA sequencing of the cell cycle phases; early & late G1, S and G2/S from human ES cells in triplicate.
Project description:Specification to primordial germ cells (PGCs) occurs under the mesoderm induction signals during gastrulation. Here, we found that Akt activation in embryonic stem (ES) cells generated self-renewing spheres during mesodermal differentiation induction and that the differentiation status of the sphere cells was in between ES cells and PGCs. Essential regulators for PGC specification and their downstream germ cell-specific genes were expressed in the spheres, showing that the cells of the sphere commenced the differentiation to germ lineage. However, the spheres could not proceed to spermatogenesis after transplantation to testes. Meanwhile, the transfer of the spheres to the original feeder-free ES cell culture conditions induced chaotic differentiation. In contrast, when the spheres were cultured on mouse embryonic fibroblasts or in the presence of ERK-cascade and GSK3 inhibitors, the reversion to the ES cell-like cell states was induced. These results indicate that the Akt signaling brings about a novel metastable and pluripotent state between ES cells and PGCs.
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.