View Program - 63rd Annual Drosophila Research Conference

Constitutively increased intracellular pH (pHi) is common to most cancers regardless of their tissue of origin or genetic background. Cancer research has traditionally focused on cancer-associated mutations and dysregulated signaling pathways. However much less is known about how changes in cellular chemistry, including pHi, regulate cancer cell behaviors. Our lab developed tools to increase pHi in the absence of other transforming mutations by over-expressing the Drosophila sodium-proton exchanger, DNhe2, in the Drosophila eye (GMR>DNhe2). We have found that GMR>DNhe2 flies have a rough eye phenotype in adult flies. To determine the underlying cause of this rough eye, we performed phenotypic analysis in larval and pupal eyes. We found the GMR>DNhe2 flies have increased proliferation in larval eyes discs. Paradoxically, we found fewer interommatidial cells at the end of patterning in pupal eyes (11.4 compared to 15 cells per counting area in control). One aim of our current work is to perform a time course analysis of cell number in GMR>DNhe2 flies to determine when in development these cells die, and to determine the mode of cell death. We next tested for genetic interactions between DNhe2 and cell death genes. We found that the pH- dependent cell death is p53-dependent but caspase independent, which is inconsistent with apoptosis, but suggests autophagy. Second, we want to identify the genes that mediate this increased cell death at higher pHi. A dominant modifier screen identified overexpression of the oncogene Myc as a strong suppressor of the GMR>DNhe2 rough eye. We tested whether this suppression is due to Myc attenuating the hyperproliferation effects of over-expressing DNhe2, but we saw no effect. Currently, we are quantifying the effects of co-expressing Myc and DNhe2 on cell number in pupal eyes. Together, our findings will elucidate mechanisms for pH-regulation of conserved, critical developmental processes and provide evidence for new paradigms in growth control.

Increased intracellular pH promotes cell death in the developing Drosophila eye

**Increased intracellular pH promotes cell death in the developing Drosophila eye**