View Program - 63rd Annual Drosophila Research Conference

20-hydroxyecdysone (20E) is a well-characterized steroid hormone required for major development changes in Drosophila. 20E surges before each larval molt, before pupariation, and during terminal differentiation of the adult structures. During molting and metamorphosis, 20E binds to its receptor to directly activate a group of early genes such as Broad-Complex (BR-C), E74 and E75, which activate late genes that are performing cell death of obsolete larval tissues, cell proliferation, etc. There is also a less well characterized pulse of 20E during mid embryogenesis. Previous studies indicate a role for 20E signaling in germband retraction, head involution, dorsal closure, and cuticle secretion. To gain a mechanistic understanding of the function of the 20E during embryogenesis, we are characterizing two Halloween mutants, disembodied (dib) and shroud (sro). These genes encode biosynthetic enzymes required for 20E synthesis. Using confocal microscopy of fixed and live wild-type and mutant embryos, we are examining the signaling and cytoskeletal dynamics required for dorsal closure. In addition, we conducted RNA sequencing of wild-type and mutant 9- and 13-hour embryos and found approximately 2000 genes that are differentially expressed between wild-type and mutant embryos. Gene ontology analysis identified genes involved nucleic acid binding and transferase activity to be significantly over represented in this collection. Interestingly, among the top 50 20E-induced genes, 11 encode Inc RNA or Antisense RNA. To extend this study, we are using RNA interference and loss-of-function mutants of 20E induced genes to investigate their role in dorsal closure.

Investigating the role of Ecdysone signaling during mid embryogenesis using Halloween genes