Decapentaplegic

Decapentaplegic (dpp) is a gene in Drosophila melanogaster that encodes a secreted signaling molecule of the Transforming Growth Factor-beta (TGF-β) superfamily, a member of the bone morphogenetic protein (BMP) family. It functions as a morphogen that patterns tissues during embryonic development and organogenesis.

Biochemical function: Dpp is produced as a precursor protein that is proteolytically processed to a mature ligand. It binds to a receptor complex consisting of the type II receptor Punt and the type I receptor Thickveins (Tkv). Upon receptor activation, the signaling cascade phosphorylates the SMAD protein Mothers against dpp (Mad), which forms a complex with Medea and translocates to the nucleus to regulate transcription of target genes.

Expression and gradient: In early embryos, dpp is expressed dorsally and forms a gradient essential for dorsal-ventral axis specification. In wing and leg imaginal discs, dpp is expressed at the anterior-posterior boundary and later in additional tissues, where it acts as a long-range morphogen to control growth and patterning, including vein formation. Its diffusion is modulated by Sog (short gastrulation) and other antagonists such as Tsg, shaping the gradient.

Roles and function: Embryonically, Dpp signaling promotes dorsal cell fates and cooperates with other pathways, such as Dorsal and Toll, to establish dorsoventral patterning. In imaginal discs, it regulates tissue growth and patterning, contributing to wing blade development and vein specification.

Evolution and genetics: Dpp is the Drosophila homolog of vertebrate BMP2 and BMP4, with conserved signaling mechanisms across species. Mutations in dpp cause defects in dorsal-ventral patterning and tissue morphogenesis, while misexpression can lead to aberrant growth and patterning.