β-catenin and Hoxa9 preserve DNA replication dynamics, genomic integrity and stem cell functionality in a Prmt1-dependent manner [CUT&RUN]

Replication stress is a main driver of functional decline of hematopoietic stem cells (HSCs), which carry the highest burden of maintaining genomic integrity and functionality within the hematopoietic system. Here, we identify a novel signaling axis in which β-catenin and Hoxa9 function in a compensatory manner to preserve HSC functionality by protecting DNA replication dynamics and genomic integrity, in part via regulation of Prmt1 activity. Co-inactivation of β-catenin and Hoxa9 induces severe hematopoietic defects accompanied by accumulating replication stress and DNA damage resulting in functional HSC decline. Furthermore, we illustrate how β-catenin and Hoxa9 pathways converge on the pivotal downstream target, Prmt1, which functions to maintain an adequate supply of DNA replication and repair factors. Prmt1 aids in alleviating replication stress and DNA damage accumulation thereby preserving HSC integrity and functionality. CUT&RUN was performed using 0.5 million HSPCs from WT BL6 mice or Ctnnb1-Biotin-3xFLAG knockin mice (JAX:029511) according to Epicypher CUT&RUN Protocol V2.0.