LeX is expressed by principle progenitor cells in the embryonic nervous system, is secreted into their environment and binds Wnt-1.

LeX/SSEA1/CD15 is an extracellular matrix-associated carbohydrate expressed by ES cells and by adult neural and bone marrow stem cells. It is important for cell adhesion, compaction and FGF2 responses of early embryonic stem cells; however, its function at later stages is not clear. We now show that LeX is expressed by primary mouse neural progenitor cells, including neural stem cells, neuroblasts and glioblasts, but not by their more differentiated products. LeX distinguishes highly proliferative cells even in the primitive neuroepithelium, demonstrating heterogeneity in cell potential before radial glia arise. At later stages, LeX expressing progenitors are frequently radial in morphology. Surface LeX expression can be used to enrich neural stem and progenitor cells from different CNS regions throughout development by FACS. We found that LeX expression is particularly strong in neural regions with prolonged neurogenesis, e.g., the olfactory epithelium, hippocampus, basal forebrain and cerebellum. These regions also express high levels of the growth factors FGF8 and/or Wnt-1. We show here that LeX-containing molecules in the developing nervous system bind Wnt-1. Our findings suggest that LeX, which is present on the surface of principle neural progenitors and secreted into their extracellular niche, may bind and present growth factors important for their proliferation and self-renewal.