Project description:Progenitor cells maintain self-renewing tissues throughout life by sustaining their capacity for proliferation while suppressing cell cycle exit and terminal differentiation. DNA methylation provides a potential epigenetic mechanism for the cellular memory needed to preserve the somatic progenitor state through repeated cell divisions. DNA methyltransferase 1 (DNMT1) maintains DNA methylation patterns after cellular replication. Although dispensable for embryonic stem cell maintenance, a clear role for DNMT1 in maintaining the progenitor state in constantly replenished somatic tissues, such as mammalian epidermis, is uncharacterized. Here we show that DNMT1 is essential for supporting epidermal progenitor cell function. DNMT1 protein was found enriched in undifferentiated cells, where it was required to retain proliferative stamina and suppress differentiation. In tissue, DNMT1 depletion led to exit from the progenitor cell compartment, premature differentiation and eventual tissue loss. These effects correlated with DNA methylation as genome-wide analysis revealed that a significant portion of epidermal differentiation gene promoters were methylated in self-renewing conditions but were subsequently demethylated during differentiation.
Project description:Progenitor cells maintain self-renewing tissues throughout life by sustaining their capacity for proliferation while suppressing cell cycle exit and terminal differentiation. DNA methylation provides a potential epigenetic mechanism for the cellular memory needed to preserve the somatic progenitor state through repeated cell divisions. DNA methyltransferase 1 (DNMT1) maintains DNA methylation patterns after cellular replication. Although dispensable for embryonic stem cell maintenance, a clear role for DNMT1 in maintaining the progenitor state in constantly replenished somatic tissues, such as mammalian epidermis, is uncharacterized. Here we show that DNMT1 is essential for supporting epidermal progenitor cell function. DNMT1 protein was found enriched in undifferentiated cells, where it was required to retain proliferative stamina and suppress differentiation. In tissue, DNMT1 depletion led to exit from the progenitor cell compartment, premature differentiation and eventual tissue loss. These effects correlated with DNA methylation as genome-wide analysis revealed that a significant portion of epidermal differentiation gene promoters were methylated in self-renewing conditions but were subsequently demethylated during differentiation. Gene expression analysis: To establish a differentiation signature for primary human keratinocytes, total RNA was isolated in biologic duplicate from cells cultured in growth conditions and high calcium differentiation conditions and hybridized to Affymetrix HG-U133 2.0 Plus arrays. This gene signature was also compared to DNMT1 deficient cells cultured in growth conditions. Methylated DNA profiling: To globally characterize DNA methylation in primary human keratinocytes, genomic DNA was immunoprecipitated using a 5-methylcytidine antibody, amplified, and hybridized to NimbleGen HG18 promoter tiling arrays. Profiling was done using DNA isolated in growth conditions as well as differentiation conditions.
Project description:Skeletal muscle is a highly organized and regenerative tissue that maintains its homeostasis primarily by activation and differentiation of muscle stem cells. Mimicking an in vitro skeletal muscle differentiation program that contains self-renewing adult muscle stem cells and aligned myotubes has been challenging. Here, we set out to engineer a biomimetic skeletal muscle construct that can self-regenerate and produce aligned myotubes using induced myogenic progenitor cells (iMPCs), a heterogeneous culture consisting of skeletal muscle stem, progenitor and differentiated cells. Utilizing electrospinning, we fabricated polycaprolactone (PCL) substrates that enabled iMPC-differentiation into aligned myotubes by controlling PCL fiber orientation. Newly-conceived constructs contained highly organized multinucleated myotubes in conjunction with self-renewing muscle stem cells, whose differentiation capacity was augmented by Matrigel supplementation. Additionally, we demonstrate using single cell RNA sequencing (scRNA-seq) that iMPC-derived constructs faithfully recapitulate a step-wise myogenic differentiation program. Notably, when the constructs were subjected to a damaging myonecrotic agent, self-renewing muscle stem cells rapidly differentiated into aligned myotubes, akin to skeletal muscle repair in vivo. Taken together, we report on a novel in vitro system that mirrors myogenic regeneration and muscle fiber alignment, and can serve as a platform to study myogenesis, model muscular dystrophies or perform drug screens.
Project description:Many studies have already shown the reprogramming of somatic cells into other cell types such as neural stem cells, blood progenitor cells, and hepatocytes by inducing combinations of transcription factors. One of the recent development in cellular reprogramming is the direct reprogramming, that can change cell fate towards different lineages. This strategy provides an alternative to the use of pluripotent stem cells ruling out the concerns of tumorigenicity caused by undifferentiated cell populations. Here, we generated induced oligodendrocyte progenitor cells (iOPCs) from mouse fibroblasts by direct reprogramming. The generated iOPCs are homogenous, self-renewing, and multipotent. Once differentiated, the somatic stem cells exhibit morphological and molecular characteristics of oligodendrocyte progenitor cells (OPCs). Thus, we demonstrated that terminally differentiated somatic cells can be converted into functional iOPCs by induction of transcription factors offering a new strategies to cure myelin disorders. To identify the global gene expression profiles of iOPCs, we analyzed total 6 samples.
Project description:DNA methylation is an important epigenetic modification that is thought to contribute to the maintenance of genomic integrity in somatic cells, in part through the silencing of transposable elements (TEs). In this study we used CRISPR/Cas9 mediated gene editing to disrupt DNMT1, the key maintenance methyltransferase in somatic human cells. Surprisingly, and in contrast to findings in mouse, inactivation of DNMT1 in human neural progenitor cells (hNPCs) resulted in viable proliferating cells that maintained the expression of appropriate marker genes. Removal of DNA methylation in hNPCs resulted in a specific activation of hominid-specific LINE-1 elements (L1s), while other classes of TEs remained silent. We also found that the transcriptionally activated L1s acted as alternative promoters for many protein-coding genes involved in neuronal functions, uncovering an L1-based transcriptional network influencing neuronal protein-coding genes. Our results prove novel mechanistic insight into the role of DNA methylation in somatic human cells.
Project description:Many studies have already shown the reprogramming of somatic cells into other cell types such as neural stem cells, blood progenitor cells, and hepatocytes by inducing combinations of transcription factors. One of the recent development in cellular reprogramming is the direct reprogramming, that can change cell fate towards different lineages. This strategy provides an alternative to the use of pluripotent stem cells ruling out the concerns of tumorigenicity caused by undifferentiated cell populations. Here, we generated induced oligodendrocyte progenitor cells (iOPCs) from mouse fibroblasts by direct reprogramming. The generated iOPCs are homogenous, self-renewing, and multipotent. Once differentiated, the somatic stem cells exhibit morphological and molecular characteristics of oligodendrocyte progenitor cells (OPCs). Thus, we demonstrated that terminally differentiated somatic cells can be converted into functional iOPCs by induction of transcription factors offering a new strategies to cure myelin disorders.
Project description:Testicular development and function relies on interactions between somatic cells and the germline, but similar to other organs, regenerative capacity decline in aging and disease. Whether the adult testis maintains a reserve progenitor population with repair or regenerative capacity remains uncertain. Here, we characterized a recently identified mouse testis interstitial population expressing the transcription factor Tcf21. We found that Tcf21+ cells are bipotential somatic progenitors present in fetal testis and ovary, maintain adult testis homeostasis during aging, and act as reserve somatic progenitors following injury. In vitro, Tcf21+ cells are multipotent mesenchymal progenitors which form multiple somatic lineages including Leydig and myoid cells. Additionally, Tcf21+ cells resemble resident fibroblast populations reported in other organs having roles in tissue homeostasis, fibrosis, and regeneration. Our findings reveal that the testis, like other organs, maintains multipotent mesenchymal progenitors that can be leveraged in development of future therapies for hypoandrogenism and/or infertility.
Project description:Understanding the mechanism by which embryonic stem (ES) cells self-renew is critical for the realization of their therapeutic potential. Previously it had been shown that in combination with LIF, Id proteins were sufficient to maintain mouse ES cells in a self-renewing state. Here we investigate the requirement for Id1 in maintaing ES cell self-renewal and blocking differentiation. We find that Id1-/- ES cells have a propensity to differentiate and a decreased capacity to self-renew. Chronic or acute loss of Id1 leads to a down-regulation of Nanog, a critical regulator of self-renewal. In addition, in the absence of Id1, ES cells express elevated levels of Brachyury, a marker of mesendoderm differentiation. We find that loss of both Nanog and Id1 is required for the up-regulation of Brachyury, and Id1 maintains Nanog expression by blocking the expression of Zeb1, a repressor of Nanog transcription. These results identify Id1 as an important factor in the maintenance of ES cell self-renewal and suggest a plausible mechanism for its control of lineage commitment. Wild type and Id1-/- ES cells were grown on gelatin under normal self-renewing conditions (in the presence of serum and LIF).