Immunocytochemical analysis of a novel carbohydrate differentiation antigen (CDA‐3C2) associated with olfactory and otic systems during embryogenesis in the rat

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Abstract
Carbohydrate differentiation antigens are known to display specific patterns of expression during mammalian development and are thought to participate in significant morphogenetic events. In the present study, two monoclonal antibodies that react with a novel carbohydrate differentiation antigen (CDA‐3C2) were used to analyze, by light microscopy, the spatiotemporal distribution of this unique high molecular weight antigen during embryogenesis in the rat. Correlative analysis of the development of peripheral neural structures, in which CDA‐3C2 was expressed, was carried out with an anti‐neurofilament antibody. Enzymatic digestion, combined with Western blots, reveal that the CDA‐3C2 epitope is a carbohydrate which is carried on a high molecular weight glycoprotein with a mass of greater than 1 million Daltons. Characteristic of carbohydrate antigens, immunoreactivity was found in several distinct cellular patterns: only along the apical border of cells, along lateral and basal membranes of cells, and extracellular‐like staining in the mesenchyme. During neurulation, CDA‐3C2 showed differential staining in the ectoderm, distinguishing lateral from neural regions. Following closure of the neural tube, there was a striking specificity of expression of CDA‐3C2 in the periphery, found almost exclusively in olfactory and otic epithelial structures. While CDA‐3C2 is found in placode‐derived tissues that subserve sensory transduction, it appears to be primarily associated with the supportive cells (and their secretions) in both otic and olfactory regions and less so with the sensory cells. The data suggest that a unique carbohydrate antigen on a large macromolecule may play a role in neurulation and/or morphogenesis of the placode‐derived otic and olfactory structures. © Wiley‐Liss, Inc.