Expression of S.S.E.A.-1 in the developing dorsal spinal cord of the rat

The trisaccharide 3 (α) fucosyl N-acetyl lactosamine (FAL, also known as stage-specific embryonic antigen; S.S.E.A.-1) is implicated as a regulating cell surface structure in developmental processes such as neuronal recognition and adhesion. An immunocytochemical study, using a monoclonal antibody directed against S.S.E.A.-1 (3B9 or CLB gr/2: see Tetteroo et al., 1984), was carried out on the developing (dorsal) spinal cord of the rat. In the embryonic period FAL was located in the ectoderm (at E10) and in the ventricular zone of the matrix layer (at E11), suggesting an involvement of S.S.E.A.-1 with proliferating, premigratory cells of the rat spinal cord. Between E12 and E16, S.S.E.A.-1 could be discerned in the dorsal aspect of the matrix layer. In addition, FAL was located in the dorsal aspect of the lateral funiculus; the dorsal root entrance zone, at E14. This localization implies a restriction of S.S.E.A.-1 for developing dorsal horn neurons (see Nornes and Das, 1974) as well as for ingrowing primary afferents. From E18 on, FAL could be discerned in the dorsal mantle layer. First, at E18, as three vaguely bounded 'areas' in the developing dorsal horn. Later on, S.S.E.A.-1 could be found in the ventral aspect of the substantia gelatinosa. This localization persisted in the mature spinal cord. S.S.E.A.-1 seems to be involved in the establishment and maintenance of a subset of primary afferents (Dodd and Jessel, 1986).