DEVELOPMENTAL EXPRESSION OF THE CD15 EPITOPE IN THE HIPPOCAMPUS OF THE MOUSE

The developmental expression of the 3-fucosyl-N-acetyl-lactosamine (CD 15, Le(x), SSEA-1) epitope has been examined immunohistochemically in paraffin sections of the mouse hippocampus. Labelling appeared initial ly at E10, with immunostaining of the ventricular surface of the hippo campal primordium and in the early hippocampal marginal zone. At E12 a nd E13, a group of cells in the marginal zone of the hippocampus was l abelled. From E14 to E15, CD15 immunoreactivity delineated several bou ndaries in the developing hippocampal formation. A band of labelling w as seen at these ages separating the fimbrioglial proliferative compar tment from the primary dentate neuroepithelium. During late fetal and early postnatal life (E19-P5.5), two strong bands of labelling were vi sible in the stratum lacunosum moleculare and stratum oriens of CA3, a nd in the marginal zone and deeper layers of the subiculum. The bands in CA3 corresponded in position to the earliest afferents to the hippo campus from the entorhinal cortex. In later postnatal life (from P5.5) , astrocytic CD15 labelling predominated in a mosaic camouflage patter n, as seen in the adult.