Endomucin is expressed in embryonic dorsal aorta and is able to inhibit cell adhesion

Recent studies have suggested the existence of progenitors common to hemato poietic and endothelial cells, called hemangioblasts, in, for instance, emb ryonic dorsal aorta. To identify a membrane-bound or secretory molecule reg ulating early hematopoiesis, we screened a cDNA library from dorsal aortas of embryonic day (E) 10.5 mice by a signal sequence trap method and obtaine d a clone encoding a sialoprotein, endomucin-1. Immunohistochemistry reveal ed that the endomucin-1 transcript was specifically expressed in the endoth elial cells of dorsal aorta of E10.5 mouse embryo. Overexpression of endomu cin-1 strongly inhibited adhesion and aggregation of cells, including cultu red endothelial cells from E10.5 dorsal aorta. These data suggest that endo mucin-1 may play a role in detachment of hematopoietic cells from endotheli um during early hematopoiesis. (C) 2001 Academic Press.