Stress-inducible phosphoprotein 1 (STIP1) is a critical stemness regulator in mouse embryonic stem cells and early mammalian development.

Proteostasis, maintained by a network of molecular chaperones, plays a central role in cell biology, and has emerged as a critical mechanism underlying pluripotency and development. The stress-inducible phosphoprotein 1 (STIP1) is a co-chaperone essential for proteostasis. STIP1 knockout causes embryonic lethality in mice, but its precise function during embryogenesis remains poorly understood. Here, we investigate the role of STIP1 in early development using in silico and cell-based approaches. Single-cell RNA sequencing data reveals that Stip1 is co-expressed with pluripotency genes in mouse embryos, suggesting a role in stem cell maintenance. To test this, we generated mouse embryonic stem cells (mESCs) from genetically modified mice with altered Stip1/STIP1 expression. STIP1 depletion in mESCs decreases the expression of pluripotency markers, reduces proliferation, and induces apoptosis and genomic instability, whereas its overexpression enhances pluripotency markers expression, promotes proliferation, and confers protection against cellular stress. Moreover, proteins involved in cell cycle progression and DNA damage response are differentially regulated in mESCs, depending on STIP1 levels. Our findings highlight STIP1 as a pivotal regulator of the pluripotent phenotype, early embryogenesis, and cellular resilience, advancing our understanding of proteostasis in stem cell biology and organismal development, with potential implications for disease modeling and regenerative medicine.