Dally regulates Dpp morphogen gradient formation by stabilizing Dpp on the cell surface.

Area of Science:

• Developmental Biology
• Molecular Biology
• Genetics

Background:

• Decapentaplegic (Dpp) is a crucial morphogen regulating anterior-posterior patterning in developing Drosophila wings.
• Dally, a heparan sulfate proteoglycan, influences Dpp morphogen distribution and cellular responses, but its precise mechanism is unclear.

Purpose of the Study:

• To elucidate the molecular mechanism by which Dally affects the Dpp morphogen gradient.
• To characterize the activity, stability, and gradient formation of a Dally-interacting Dpp mutant.

Main Methods:

• Utilized a truncated Dpp form (Dpp(Delta N)) lacking the Dally-binding N-terminal domain.
• Assessed Dpp(Delta N) activity and stability in vitro and in vivo.
• Performed genetic interaction experiments with the Dpp type I receptor, Thickveins (Tkv).

Main Results:

• Dpp(Delta N) exhibited similar in vitro activity and stability to wild-type Dpp but had a shorter in vivo half-life, indicating Dally stabilizes Dpp extracellularly.
• Dally antagonized Tkv's effect on Dpp signaling.
• Dally likely inhibits Tkv-mediated endocytosis and degradation of the Dpp-receptor complex.

Conclusions:

• Dally stabilizes the Dpp morphogen in the extracellular matrix.
• Dally regulates Dpp signaling by inhibiting receptor-mediated internalization and degradation.
• This reveals a novel mechanism for Dally's role in controlling Dpp distribution and signaling pathways.