Endoplasmic reticulum transmembrane protein involved in vesicle-mediated transport, which is required for neutrophil function. Required for vesicle-mediated transport; it is however unclear whether it is involved in early secretory pathway or intracellular protein transport. Acts as a regulator of neutrophil function, probably via its role in vesicle-mediated transport: required for defense against fungal pathogens and for granulocyte colony-stimulating factor (GM-CSF) signaling pathway; possibly by regulating glycosylation and/or targeting of proteins contributing to the viability and migration of neutrophils. Interacts with COPA, COPB2 and COPG2. Lethality around embryonic day 8.5. Mice carrying a hematopoietic lineage-specific deletion of Jagn1 show defects in neutrophil-dependent immune response to the fungal pathogen Candida albicans. Neutrophils display defects in the glycosylation of proteins involved in cell adhesion and cytotoxicity as well as impaired migration in response to Candida albicans infection and impaired formation of cytotoxic granules. Belongs to the jagunal family. Experiments in human confirm the importance of JAGN1 in neutrophil function with some differences. Defects in JAGN1 cause neutropenia in human, while it is not the case in mice lacking Jagn1. Mutant mice show defects in neutrophil migration and increased susceptibility to fungal infections due to defective killing capacity of neutrophil granulocytes.