SAMHD1 as a metabolic and genomic gatekeeper in human naïve pluripotent stem cells

Human pluripotent stem cells (hPSCs) are characterised by specific transcriptional, epigenetic and functional features, which result in their extended capacity to give rise to all embryonic and extraembryonic cell types in vitro and in vivo. Despite their fundamental importance in the initial phase of human development, the regulation of deoxyribonucleotide triphosphate (dNTP) metabolism to sustain DNA replication and maintain genome integrity in hPSCs remains unexplored. In this study, we investigated the role of the dNTPase SAMHD1 using transcriptional analyses, biochemical quantification of dNTP pools and telomere length determination. To enable controlled modulation of gene expression in hPSCs, we employed an inducible CRISPR interference (CRISPRi) system targeting SAMHD1. This experimental framework made it possible to delineate the contribution of SAMHD1 to dNTP homeostasis within the pluripotent state and to explore the broader cellular consequences associated with its perturbation, including effects on cell proliferation and genome stability. Altogether, the findings of this thesis establish SAMHD1 as both a metabolic and genomic gatekeeper, highlighting its critical role as a central regulator of nucleotide metabolism in hPSCs, and the implemented approach provides a versatile platform to further explore SAMHD1-related phenotypes in development and disease, including the Aicardi–Goutières syndrome.