IG-molecule Kilon shows differential expression pattern from LAMP in the developing and adult rat hippocampus

Cell recognition molecules of the immunoglobulin superfamily are involved i n the formation, establishment, and plasticity of neural circuits in the ce ntral nervous system (CNS). We used a polymerase chain reaction-based appro ach to specifically amplify molecules with conserved sequence elements of: immunoglobulin-like domains. This approach enabled us to isolate Kilon, a n ovel immunoglobulin that has been described by Funatsu et al. (J Biol Chem 1999;274: 8224-8230) from the hippocampus. The sequence of Kilon shows a hi gh degree of homology to that of the chicken protein neurotractin, a molecu le involved in neurite outgrowth and capable of interacting with LAMP. In s itu hybridization analysis was performed to analyze the Kilon mRNA distribu tion in the developing and adult rat brain and to compare it to that of LAM P mRNA. Kilon mRNA,was found to be specifically expressed in the dentate gy rus (DC) of the adult rat, whereas LAMP transcripts were present in all reg ions of the hippocampal formation. These results were corroborated by RT-PC R semiquantification of gene expression in microdissected tissue prepared f rom the DC and the CA1 region of the:hippocampus. We also performed mRNA ex pression-analysis of both genes following hippocampal deafferentation and s eizure, but neither Kilon nor LAMP gene expression showed significant alter ations after lesioning on the in situ hybridization level. Our results show that the expression patterns of Ki(on and LAMP during development and in t he mature hippocampus are clearly distinguishable from one another, which s uggests different roles for these related molecules in the hippocampus. Hip pocampus 2000;10 632-644. (C) 2000 Wiley-Liss, Inc.