G2 ARREST OF CELL-CYCLE ENSURES A DETERMINATION PROCESS OF SENSORY MOTHER CELL-FORMATION IN DROSOPHILA

In Drosophila, the sensory mother cells of macrochaetes are chosen fro m among the mitotically quiescent clusters of cells in wing imaginal d iscs, where other cells are proliferating. The pattern of cyclin A, on e of the G2 cyclins, reveals that mitotically quiescent clusters of ce lls are arrested in G2. When precocious mitoses are induced during sen sory mother cell determination by the ectopic expression of String, a known G2/M transition regulator, the formation of sensory mother cells is disturbed, resulting in the loss of macrochaetes in the adult notu m. This suggests that G2 arrest of the cell cycle ensures the proper d etermination of sensory mother cells.