The localization and expression of HNK-1-immunoreactive molecules in chicken embryos

HNK-1 (Leu-7 antigen) is a unique carbohydrate moiety bound to the subsets of a number of cells and extracellular matrix glycolipids and glycoproteins, acting as an adhesive. Using immunohistochemistry and Western immunoblot method, we observed the localization and expression of the HNK-1 epitope in chicken embryos at different developmental stages. The results of immunohistochemistry show that HNK-1-immunoreactivity (HNK-1-IR) is distributed extensively in different tissues, and the intensity of immunoreaction varies with the development stages in chicken embryos. In the nervous system, the HNK-1-IR decreases gradually in brain but remains almost stable in spinal cord with embryo development, and it is strong in the neural tube and the neural crest at stage 11. At later stages, all forming ganglia are labeled. The special conductive tissues of the heart are also recognized by the HNK-1 antibody. In the alimentary tube, HNK-1-IR mainly appears in the Auerbach plexus, the Meissner plexus, and the mucosal membrane. Endothelial cells, pit cells and/or fat-storing cells may contribute to the HNK-1-IR of the liver. The results of Western blot show that there are at least three kinds of HNK-1-reactive molecules expressed in different tissues of different stages, and the kinds of these molecules remain relatively identical with developmental stages. Our results from chicken embryos demonstrate that HNK-1 epitope is expressed widely in the entire embryonic period, and the distribution of HNK-1-positive molecules shows histological specificity.