Daxx maintains endogenous retroviral silencing and restricts cellular plasticity in vivo.

Abstract

Tumor sequencing studies have emphasized the role of epigenetics and altered chromatin homeostasis in cancer. Mutations in <i>DAXX</i>, which encodes a chaperone for the histone 3.3 variant, occur in 25% of pancreatic neuroendocrine tumors (PanNETs). To advance our understanding of physiological functions of Daxx, we developed a conditional <i>Daxx</i> allele in mice. We demonstrate that <i>Daxx</i> loss is well tolerated in the pancreas but creates a permissive transcriptional state that cooperates with environmental stress (inflammation) and other genetic lesions (<i>Men1</i> loss) to alter gene expression and cell state, impairing pancreas recovery from inflammatory stress in vivo. The transcriptional changes are associated with dysregulation of endogenous retroviral elements (ERVs), and dysregulation of endogenous genes near ERVs is also observed in human PanNETs with <i>DAXX</i> mutations. Our results reveal a physiologic function of DAXX, provide a mechanism associated with impaired tissue regeneration and tumorigenesis, and expand our understanding of ERV regulation in somatic cells.