The mechanism of differentiation pattern formation in the cellular slime molds as analysed by monoclonal antibodies

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1. Two types of cells (prestalk and prespore cells) differentiate in a tissue formed by aggregation of cellular slime mold cells. We tried to obtain monoclonal antibodies specific for each cell type and produced four prespore specific antibodies. Antigens reactive with the antibodies are localized in prespore vacuoles specifically formed in prespore cells and released from the cells upon sporulation to constitute spore coat. By using polyclonal antibodies produced against a molecular species of spore coat proteins, a cDNA library was screened to obtain a prespore specific cDNA clone and a gene for this clone is being isolated. After the gene is obtained, we will examine its structure and regulation of expression together with those of other genes specifically expressed in prespore cells.2. As stalk and prestalk specific proteins, we purified a WGA binding protein (31Kd) and a protein (35Kd) reactive with a cell type-nonspecific monoclonal antibody, but failed to produce monoclonal and polyclonal antibodies for either of them. On the other hand, prestalk specific cDNA clones were used to obtain a large amount of specific proteins, against which we are in the process of producing specific antibodies.3. Some of polyclonal antispore antibodies and prespore specific monoclonal antibodies were found to cross-react with antigens of different species of not only Dictyostelium but also Polysphondylium. As cell differentiation in the latter species has not been well elucidated, we are investigating the process of pattern formation by the use of these antibodies.4. A mutant in which prestalk and prespore cells fail to sort out to produce the two presumptive regions was isolated and we are trying to examine the abnormality of the mutant at protein levels.