Metabolic and transcriptional crosstalk at the onset of pluripotent stem cell differentiation
File(s)
Author(s)
de Souza, Roshni
Type
Thesis
Abstract
The peri-implantation stage of embryonic development is associated with remodelling of the transcriptome, epigenome, and metabolome of the pluripotent compartment. Metabolic remodelling has long been regarded as a consequence of the changing environment of the implanting embryo. However, mounting evidence suggests a crucial role for metabolic pathways in maintaining the balance between stem cell potency and differentiation.
Our lab has previously reported that pre-implantation mouse embryos can accumulate lipids in the form of lipid droplets (LDs), which are subsequently mobilised during implantation for epithelialisation of the epiblast. In this study, we investigated the mechanisms underlying this build-up of neutral lipids in the epiblast using mouse embryonic stem cells (ESCs). We uncovered that ESCs grown in the presence of animal-derived serum and Leukemia Inhibitory Factor (LIF) exhibit a high degree of heterogeneity in LD size and number. Isolation of ESC clones harbouring differential LD content highlighted the existence of metabolic heterogeneity in ESCs. Here we established that these differences in lipid storage underlie distinct metabolic and pluripotent states. Notably, we showed that lipid-rich ESCs represent a more advanced differentiation state. Using these lipid ESC clones as a model for discrete steps at the onset of differentiation, we identified enhanced oxidative activity concomitant with increased citrate production and lipogenesis, at the exit of naive pluripotency.
To identify putative factors that may drive this transitional pluripotent and metabolic state, we profiled the landscape of chromatin-bound proteins in lipid-rich and lipid-poor ESCs, using chromatin enrichment for proteomics (ChEP). Our results underscored a link between the metabolic and pluripotent state of ESCs and a distinct epigenetic axis, regulated by 2-cell factor Zinc finger and SCAN domain containing 4 (ZSCAN4). Mechanistically, we demonstrated that ZSCAN4 is induced within a specific metabolic and pluripotent state in ESCs, associated with the shortening of telomeres. Given the previously described role of ZSCAN4 in telomere maintenance, we propose a metabolism-driven ZSCAN4 induction at the onset of pluripotent stem cell differentiation. This represents an important check-point for genomic integrity as cells transition from a naive to primed state of pluripotency, with potential impact on the survival and developmental capacity of these cells.
Our lab has previously reported that pre-implantation mouse embryos can accumulate lipids in the form of lipid droplets (LDs), which are subsequently mobilised during implantation for epithelialisation of the epiblast. In this study, we investigated the mechanisms underlying this build-up of neutral lipids in the epiblast using mouse embryonic stem cells (ESCs). We uncovered that ESCs grown in the presence of animal-derived serum and Leukemia Inhibitory Factor (LIF) exhibit a high degree of heterogeneity in LD size and number. Isolation of ESC clones harbouring differential LD content highlighted the existence of metabolic heterogeneity in ESCs. Here we established that these differences in lipid storage underlie distinct metabolic and pluripotent states. Notably, we showed that lipid-rich ESCs represent a more advanced differentiation state. Using these lipid ESC clones as a model for discrete steps at the onset of differentiation, we identified enhanced oxidative activity concomitant with increased citrate production and lipogenesis, at the exit of naive pluripotency.
To identify putative factors that may drive this transitional pluripotent and metabolic state, we profiled the landscape of chromatin-bound proteins in lipid-rich and lipid-poor ESCs, using chromatin enrichment for proteomics (ChEP). Our results underscored a link between the metabolic and pluripotent state of ESCs and a distinct epigenetic axis, regulated by 2-cell factor Zinc finger and SCAN domain containing 4 (ZSCAN4). Mechanistically, we demonstrated that ZSCAN4 is induced within a specific metabolic and pluripotent state in ESCs, associated with the shortening of telomeres. Given the previously described role of ZSCAN4 in telomere maintenance, we propose a metabolism-driven ZSCAN4 induction at the onset of pluripotent stem cell differentiation. This represents an important check-point for genomic integrity as cells transition from a naive to primed state of pluripotency, with potential impact on the survival and developmental capacity of these cells.
Version
Open Access
Date Issued
2023-02-02
Date Awarded
2023-06-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Azuara, Veronique
Sponsor
Imperial College London
Biotechnology and Biological Sciences Research Council (Great Britain)
Publisher Department
Department of Metabolism, Digestion and Reproduction
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)