Unveiling a novel role for p19Arf (alternative reading frame) in mESC differentiation toward the pancreatic lineage

: The tumor suppressor ARF (p14 in human, p19 in mouse), has traditionally been characterized by its pivotal role in tumor surveillance. However, its involvement in an expanding range of cellular processes reveals that its functions are broader and more complex than initially appreciated. Here, we uncover a previously unrecognized role of p19ARF in endodermal differentiation, specifically in pancreatic lineage specification using an in vitro differentiation model of mouse embryonic stem cells (mESCs). Using CRISPR/Cas9-mediated mutagenesis, we show that mESCs with mutations in p19Arf are unable to efficiently differentiate towards pancreatic endoderm. Transcriptomic profiling reveals substantial alterations in gene networks associated not only with lineage commitment but also with cytoskeletal organization and cell morphology. These changes correlate with a disruption in stem cell architecture and suggest the persistence of pluripotency feature when only one copy of functional p19Arf is present. Taken together, our findings highlight a role for p19Arf in modulating endodermal differentiation while maintaining the essential cellular properties of stem cells, thus expanding its relevance beyond tumor suppression.