Immunohistochemical Localization of a β-Galactoside-Binding Lectin in Rat Central Nervous System

From a lectin isolated from human brain (HBL-14), that specifically binds β-galactosides, a polyclonal antiserum was raised that also recognizes a similar rat brain lectin (RBL-16). These antibodies allowed the immunocytochemical localization of the lectin during rat brain development by optical and electron microscopy. The presence of RBL-16, first detected at embryonic day 15, was specially increased from postnatal day 1 to 10. Its level decreased there after but it could still be detected in adult rat brain. The lectin, predominantly neuronal until postnatal day 13, was also present in astrocytes and perivascular cells where no developmental regulation was observed in contrast to neurons. Electron microscopy showed that the lectin was transiently expressed in the axoplasm of almost all neurons in layer I around the birth date, after which it remained inside neurons, including cell bodies and dendrites, in all examined regions. The lectin was clearly localized in postsynaptic structures. This β-galactoside-specific lectin may be involved in synaptogenesis and neurite fasciculation as well as in intracellular traffic as discussed.