The development of leukemia in hemocytes of the soft-shell clam presents a non-mammalian model system in which to study the expression of normal and tumor- specific proteins. The proposed work focuses on recently discovered proteins expressed by normal and leukemic hemocytes. Protein sequence data will be obtained, and a cDNA library made from leukemic cells will be screened with monoclonal and polyclonal antibodies made to the a 150 kD protein expressed predominantly in leukemic cells, as well as a 130 kD protein expressed predominantly in normal hemocytes. Sequences obtained will then be compared to known genes in order to obtain information on the function of these gene products. Studies will be carried out to localize the expression of these proteins following sub- cellular fractionation. In addition, if the genes encoding these proteins can be isolated, analysis of expression in clam tissues will be carried out using nucleic acid probes. These proposed studies will be carried out using FACS analysis, production of murine monoclonal antibodies, protein sequencing, cDNA cloning, Western, Southern, and Northern blotting, and fluorescence and confocal microscopy.