['Modification of Notch receptors by O-linked fucose and its further elongation by the Fringe family of glycosyltransferase has been shown to be important for Notch signaling activation. Our recent studies disclose a myeloproliferative phenotype, hematopoietic stem cell (HSC) dysfunction, and abnormal Notch signaling in mice deficient in FX, which is required for fucosylation of a number of proteins including Notch. The purpose of this study was to assess the self-renewal and stem cell niche features of fucose-deficient HSCs.', 'Homeostasis and maintenance of HSCs derived from FX(-/-) mice were studied by serial bone marrow transplantation, homing assay, and cell cycle analysis. Two-photon intravital microscopy was performed to visualize and compare the in vivo marrow niche occupancy by fucose-deficient and wild-type (WT) HSCs.', 'Marrow progenitors from FX(-/-) mice had mild homing defects that could be partially prevented by exogenous fucose supplementation. Fucose-deficient HSCs from FX(-/-) mice displayed decreased self-renewal capability compared with the WT controls. This is accompanied with their increased cell cycling activity and suppressed Notch ligand binding. When tracked in vivo by two-photon intravital imaging, the fucose-deficient HSCs were found localized farther from the endosteum of the calvarium marrow than the WT HSCs.'] Do fucose-deficient hematopoietic stem cells have decreased self-renewal and aberrant marrow niche occupancy?