UNDEREXPRESSION OF A NOVEL GENE, DIA2, IMPAIRS THE TRANSITION OF DICTYOSTELIUM CELLS FROM GROWTH TO DIFFERENTIATION

In Dictyostelium discoideum Ax-2 cells, a specific point (PS-point) in the cell cycle from which they initiate differentiation in response t o starvation has been specified. Using synchronized Ax-2 cells and the differential display method, a novel gene (differentiation-associated gene 2; dia2) was isolated as one of the genes expressed specifically during the shift of Ax-2 cells from growth to differentiation. The di a2 gene codes a lysine- and leucine-rich protein with a predicted mole cular mass of 16.9 kDa. Northern blot analysis has shown that the dia2 mRNA, of 0.7 kb, accumulates in differentiating cells starved just be fore the PS-point, while there is no detectable expression in vegetati vely growing cells. Antisense-mediated gene inactivation of dia2 great ly inhibited the progress of differentiation, presumably through the r educed expression of cAMP receptor 1 (car1). Thus, the DIA2 expression was suggested to have an essential role in the initiation of differen tiation, closely relating to the cAMP signaling system. (C) 1998 Acade mic Press.