DIFFERENTIAL LAMININ ISOFORM EXPRESSION IN THE DEVELOPING RAT OLFACTORY SYSTEM

Members of the laminin family influence mammalian cells in a variety o f ways, mediating adhesion, proliferation, migration, and growth of ne uronal processes. Specific laminin domains act through a number of cel lular interaction sites to mediate these activities. In the developing olfactory system, axons grow from the olfactory epithelium to synapti c sites in the olfactory bulb through a matrix rich in laminins and kn own mediators of laminin-axon interactions include integrins and a gal ectin-1/glycoconjugate adhesion system. Using biochemistry, immunocyto chemistry, and in situ hybridization, we identified alpha 2, alpha 3, beta 1, beta 2 and gamma 1 laminin isoforms in the late embryonic and neonatal rat olfactory system. However, alpha 1-containing laminin cou ld not be detected in association with olfactory neurons. Immunocytoch emistry revealed that beta 2 laminin is preferentially expressed in th e ventral and lateral nerve layer of the olfactory bulb and in the mai n olfactory axon tracks, but is undetectable in the accessory system d uring embryonic and early postnatal development. In contrast, beta 1 a nd gamma 1 laminins are evenly distributed throughout the olfactory bu lb and in both the main and accessory olfactory axon tracks. The diffe rential localization of laminin chains in vivo is likely to have funct ional significance for the development and maintenance of the olfactor y system. (C) 1997 Elsevier Science B.V.