Activity is observed in all cardial cells of the embryo and early larvae. Expression diminishes in second instar larvae, becomes restricted to a single pair of valve cells in third instar larvae, and to the three pairs of valve cells in adults, where it is maintained throughout the lifetime. It is also active in adult alary muscles. Activty is also observed in anterior cardiomyocytes immediately anterior to the valve cells. It is also observed in unidentified cells in the brain and ventral nerve cord.