The intestinal stem cell/enteroblast-GAL4 driver, escargot-GAL4, also manipulates gene expression in the juvenile hormone-synthesizing organ of Drosophila melanogaster

Abstract

Intestinal stem cells (ISCs) of the fruit fly, Drosophila melanogaster, offer an excellent genetic model to explore homeostatic roles of ISCs in animal physiology. Among available genetic tools, the escargot (esg)-GAL4 driver, expressing the yeast transcription factor gene, GAL4, under control of the esg gene promoter, has contributed significantly to ISC studies. This driver facilitates activation of a gene of interest in proximity to a GAL4-binding element, UAS, in ISCs and progenitor enteroblasts (EBs). While esg-GAL4 has been considered an ISC/EB-specific driver, its actual specificity remains unexplored. In this study, we reveal esg-GAL4 expression in the corpus allatum (CA), responsible for juvenile hormone (JH) production. When driving the oncogenic gene Ras^V12, esg-GAL4 induces overgrowth in ISCs/EBs as reported, but also increases CA cell number and size. Consistent with this observation, animals alter expression of JH-response genes. Our data show that esg-GAL4-driven gene manipulation can systemically influence JH-mediated animal physiology, arguing for cautious use of esg-GAL4 as a “specific” ISC/EB driver to examine ISC/EB-mediated animal physiology.