Developmental expression of the CD15 epitope in the hippocampus of the mouse

The developmental expression of the 3-fucosyl-N-acetyl-lactosamine (CD15, Lex, SSEA-1) epitope has been examined immunohistochemically in paraffin sections of the mouse hippocampus. Labelling appeared initially at E10, with immunostaining of the ventricular surface of the hippocampal primordium and in the early hippocampal marginal zone. At E12 and E13, a group of cells in the marginal zone of the hippocampus was labelled. From E14 to E15, CD15 immunoreactivity delineated several boundaries in the developing hippocampal formation. A band of labelling was seen at these ages separating the fimbrioglial proliferative compartment from the primary dentate neuroepithelium. During late fetal and early postnatal life (E19-P5. 5), two strong bands of labelling were visible in the stratum lacunosum moleculare and stratum oriens of CA3, and in the marginal zone and deeper layers of the subiculum. The bands in CA3 corresponded in position to the earliest afferents to the hippocampus from the entorhinal cortex. In later postnatal life (from P5.5), astrocytic CD15 labelling predominated in a mosaic camouflage pattern, as seen in the adult.