AML1 may prove to be similarly versatile, but Phil says that because it is much easier to manipulate genes in Drosophilia, studies of the role of lozenge in eye development should illuminate the role of AML1 in human cells. It comprises 750 ommatidia, or individual eyes. It's a beautiful reiterated, almost crystalline structure, so any defects are immediately obvious. Phil has been collaborating with Dr John Pollock, of Carnegie-Mellon University in Pittsburgh, to determine how lozenge influences eye development. They have found that lozenge affects the recruitment of more than half the cells that form the ommatidium.
Some mutations cause cells in the imaginal disk to assume the wrong identity or to die.
Cells that suffer the latter fate have led Phil and John to propose a controversial role for the lozenge gene in apoptosis, or programmed cell death. We believe lozenge keeps cells alive until they have the opportunity to achieve the right identity. The cells die because lozenge fails to repress genes in the programmed cell death pathway, which is their default pathway. Proof that lozenge is an apoptosis gene would be very significant. An understanding of how lozenge influences the life and death of eye cells in Drosophila could provide insights into how mutations in the AML1 gene trigger leukaemia-and possibly other forms of cancer in humans.