Plant & Animal Genomes XI Conference

January 11-15, 2003
Town & Country Convention Center
San Diego, CA

Poster: Aquaculture
            

GENOMIC ORGANIZATION AND EXPRESSION OF A CD45 HOMOLOG IN CHANNEL CATFISH, ICTALARUS PUNCTATUS.

Dept. Microbiology, University of Mississippi Medical Center, 2500 North State Str., Jackson, MS, 39216, USA

The transmembrane phosphatase CD45 plays an important role in T and B cell receptor and cytokine signaling by maintaining receptor associated kinases in an active state. A prominent feature of CD45 is alternative splicing within its amino-terminal region, resulting in the generation of several isoforms, the expression of which are tightly regulated and dependent on the developmental and activation state of the lymphocyte. Nevertheless, the significance of such alternative splicing and the functional roles of generated isoforms in mammals are poorly understood. Our studies have demonstrated that the organization of alternatively spliced exons of catfish CD45 genes is dissimilar to those of homologous genes in other animals. Unlike mammalian CD45, where only three exons are involved in the production of alternatively spliced CD45 variants, catfish appear to use up to twelve highly similar exons which are differentially expressed depending on the activation stage of the cell. Another distinction in catfish is the presence of two separate CD45 loci; a single gene is present in mammals. The exact number of alternative exons, their organization, and functionality for each locus are being analyzed using BAC clones. Finally, immunoprecipitation experiments utilizing anti-catfish CD45 mAbs demonstrated, as for RT-PCR analysis, that different CD45 isoforms are expressed on catfish T and B cells.