Multiple roles for four-jointed in planar polarity and limb patterning

Area of Science:

• Developmental Biology
• Genetics
• Cell Biology

Background:

• Insect cuticles serve as a model for studying planar cell polarity.
• Planar cell polarity genes organize polarized hair arrangement in Drosophila adults.
• The gene four-jointed (fj) is known to influence eye polarity and limb development.

Purpose of the Study:

• To investigate the role of four-jointed in planar polarity determination in Drosophila wings and abdomens.
• To analyze the expression pattern of four-jointed during wing development.
• To understand how four-jointed influences cellular organization and development.

Main Methods:

• Analysis of four-jointed gene expression patterns in developing Drosophila wings.
• Generating clones of cells with altered four-jointed expression (null or ectopic).
• Observing and quantifying hair polarity phenotypes in wings and abdomens of mutant and wild-type flies.

Main Results:

• Four-jointed is expressed in a gradient across the developing wing.
• Loss or ectopic expression of four-jointed leads to autonomous and nonautonomous hair repolarization in wings and abdomens.
• Mutations in four-jointed also result in defects in wing vein development.
• Clones disrupting the four-jointed gradient cause polarity phenotypes.

Conclusions:

• An inferred gradient of four-jointed expression is crucial for establishing planar polarity.
• Local disruptions in the four-jointed gradient likely cause observed polarity defects.
• Four-jointed may function as a modifier of signaling pathways involved in diverse patterning processes.