Sprinter: a novel transmembrane protein required for Wg secretion and signaling

Area of Science:

• Developmental Biology
• Cell Signaling
• Molecular Genetics

Background:

• Wingless (Wg) is a crucial secreted ligand in the Wnt family, regulating cell-to-cell interactions and gene expression during development.
• Wg signaling pathway activation is dependent on extracellular ligand concentration, involving complex cellular mechanisms for synthesis, delivery, and reception.
• Understanding the precise mechanisms of Wg secretion and transport is vital for comprehending developmental processes.

Purpose of the Study:

• To identify novel factors involved in the Wingless (Wg) signaling pathway.
• To elucidate the function of the newly identified sprinter (srt) gene in Wg signal transmission.
• To determine the cellular site and specificity of Srt protein action within the Wg pathway.

Main Methods:

• Genetic screens to identify mutations affecting Wg signaling.
• Analysis of Wg target gene expression in mutant embryos and wing discs.
• Characterization of the sprinter (srt) gene and its encoded transmembrane protein.
• Comparative analysis with Hedgehog (Hh) signaling to assess pathway specificity.

Main Results:

• Identification of sprinter (srt) as a gene encoding a novel transmembrane protein essential for Wg signal transmission.
• Mutations in srt lead to the accumulation of Wg within producing cells and reduced Wg target gene activation (Engrailed, Senseless, Achaete).
• Srt function is confined to Wg-producing cells and is specific to the Wg pathway, not affecting Hedgehog signaling.

Conclusions:

• The sprinter (srt) gene product is required for the efficient secretion or release of Wingless (Wg) ligand from producing cells.
• Srt likely plays a role in Wg maturation, membrane targeting, or export, regulating the availability of functional ligand.
• Disruption of Srt function impairs Wg pathway activation in receiving cells due to a lack of secreted Wg.