Abstract 9722996 Warr The bony fish have immune systems which are similar to those of higher vertebrates but seem to be less complex. The channel catfish is a well developed experimental fish model, and also a commercially important aquacultured species. This laboratory has previously isolated and mapped the gene that encodes the heavy chain of the major antibody (IgM) of the channel catfish, and the proposed studies are focused on the mechanisms by which this gene is expressed. In this grant they will investigate the nature of the enhancer that drives transcription of this gene, and the transcription factors that are essential for the expression of the gene. In preliminary experiments they have identified the catfish transcription factor that bind to the "octamer: motif which is characteristic of immunoglobulin genes. This transcription factor and the octomer motif to which it binds appear to have undergone co-evolution. The catfish oct transcription factor has a strong functional preference for a motif that has a different sequence from that found in mammals. They propose to determine the basis for this preference by looking at the binding affinity and other protein factors that bind to DNA. The role of the transcription factor or other possible transcription factors will also be determined. These studies will not only provide information on the regulation of the catfish immunoglobulin heavy chain gene, but will provide information on regulation of immunoglobulin genes in general, and will also indicate how immunoglobulin gene expression has evolved in vertebrates. %%% Studies of the immune system in fish, show similarities and differences from the immune system of mammals. Understanding the relation of the immunoglobulin genes of the catfish, will provide information on the general regulation of immunoglobulin genes, and also will enable us to understand how immunoglublin heavy chain gene expression has evolved in vertebrates. ***
