Wnt5 and drl/ryk gradients pattern the Drosophila olfactory dendritic map

Area of Science:

• Neuroscience
• Developmental Biology
• Molecular Biology

Background:

• Dendrite development involves migration guided by environmental cues.
• The Drosophila antennal lobe (AL) olfactory map relies on projection neuron (PN) dendrite segregation.
• Mechanisms of dendritic guidance remain largely unknown.

Purpose of the Study:

• To investigate the molecular mechanisms underlying PN dendrite reordering and targeting within the developing Drosophila AL.
• To elucidate the roles of Wnt5 and its receptor Drl/Ryk in guiding PN dendrites.

Main Methods:

• Analysis of PN dendrite morphology and targeting during specific developmental stages (16-30 h after puparium formation).
• Genetic manipulation of Wnt5 and Drl/Ryk expression in AL-extrinsic neurons and PNs.
• Assessment of Wnt5 and Drl/Ryk expression patterns using in situ hybridization or antibody staining.

Main Results:

• PN dendrites undergo significant rotational reordering between 16-30 h post-puparium formation.
• AL-extrinsic neurons express Wnt5, forming a dorsolateral-high to ventromedial-low gradient.
• Loss of Wnt5 causes ventral targeting defects, while Wnt5 overexpression disrupts patterning.
• Drl/Ryk is expressed in a DL>VM gradient on PNs; its loss causes ventromedial mistargeting, suppressed by reduced Wnt5.
• Drl/Ryk overexpression leads to dorsolateral targeting, dependent on its cytoplasmic domain.

Conclusions:

• Wnt5 acts as a repulsive guidance cue for PN dendrites.
• Drl/Ryk signaling in PNs inhibits Wnt5 signaling.
• Coordinated Wnt5 and Drl/Ryk expression patterns precisely orient PN dendrites to their glomerular targets.