DPP9 enzymatic activity in hematopoietic cells is dispensable for mouse hematopoiesis

Abstract Dipeptidyl peptidase9 (DPP9) is a ubiquitously expressed intracellular prolyl peptidase implicated in immunoregulation. However, its physiological relevance in the immune systemremains largely unknown. We investigated the role of DPP9 enzyme in immune systemby characterizing DPP9 knock-in mice expressing a catalytically inactive S729A mutant of DPP9 enzyme (DPP9 ki/ki mice). DPP9 ki/ki mice show reduced number of lymphoid and myeloidcells in fetal liver and postnatal blood but their hematopoietic cells are fully functional and able to reconstitute lymphoid and myeloidlineages even in competitive mixed chimeras. These studies demonstrate that inactivation of DPP9 enzymatic activity does not lead to any perturbations in mouse hematopoiesis.