Interactions Between Two Morphogen Systems in Patterning the Dorsovental Axis of the Drosophila Melanogaster Embryo

Morphogen gradients determine cellular fates in developing organisms based on concentration-dependent gene expression. We study morphogen gradients in Drosophila melanogaster because there exist several homologs between the proteins and developmental pathways found in Drosophila and those in higher-order animals, such as humans. The bone morphogenetic protein (BMP) ligand Decapentaplegic (Dpp) is one such homolog that patterns the dorsal side of the embryo while the ventral side patterning comes from the transcription factor Dorsal (Dl). Dl and Dpp together pattern the entire dorsoventral axis, making them extremely important embryogenesis studies in Drosophila. When Dpp binds to its receptor Thickveins, the subsequent complex phosphorylates MAD, the BMP signal transducer, which then enters the nucleus to drive gene expression. Dl affects patterning on the ventral side of the embryo by repressing expression of dpp, and subsequently pMAD production. We studied the effects of constitutively active and dominant negative forms of the Thickveins receptor on the Dl and Dpp gradients to determine the nature of the interactions that occur between the two morphogens and how those interactions might influence the overall patterning of the DV axis.