Morphological domains of Lewis-X/FORSE-1 immunolabeling in the embryonic neural tube are due to developmental regulation of cell surface carbohydrateexpression

The Lewis-X (LeX) carbohydrate epitope, recognized by the FORSE-1 monoclona l antibody (mAb), shares expression boundaries with neural regulatory genes and may be involved in patterning the neural tube by creating domains of d ifferential cell adhesion. The present experiments focus on the question of what determines the expression pattern of LeX in embryonic rat brain. Comp arisons of FORSE-1-positive glycolipid and protein antigens in embryonic, e arly postnatal, and adult tissues show that the LeX epitope is carried prim arily by glycolipids during embryonic development and by a proteoglycan and glycoproteins in postnatal and adult tissue. Immunohistochemistry using FO RSE-1 and an antibody to the proteoglycan phosphacan, which carries LeX, sh ows that the distribution of LeX is more restricted than phosphacan. These observations suggest that the precise spatial regulation of FORSE-1 binding in the embryonic forebrain is due to the expression pattern of the LeX car bohydrate on glycolipids, rather than to the transcriptional regulation of a carrier protein, (C) 1999 Academic Press.