Leucine-rich repeat transmembrane proteins instruct discrete dendrite targeting in an olfactory map

Area of Science:

• Neuroscience
• Developmental Biology
• Genetics

Background:

• Olfactory systems process odor information through discrete neural pathways.
• In Drosophila, projection neurons (PNs) connect with olfactory receptor neurons (ORNs) in specific glomeruli, forming a neural map.
• Mechanisms of PN dendrite targeting to glomeruli remain largely unknown.

Purpose of the Study:

• To investigate the molecular mechanisms governing projection neuron dendrite targeting in the Drosophila olfactory system.
• To identify cell-surface molecules involved in the formation of the olfactory map.

Main Methods:

• Utilized loss-of-function and gain-of-function studies in Drosophila.
• Investigated the expression patterns of leucine-rich repeat (LRR) transmembrane proteins.
• Examined the role of Capricious (Caps) and Tartan proteins in PN dendrite targeting.

Main Results:

• Capricious (Caps) protein is differentially expressed in distinct classes of projection neurons (PNs).
• Caps expression directs the segregation of Caps-positive and Caps-negative PN dendrites to specific glomerular targets.
• PN dendrite targeting mediated by Caps is independent of presynaptic input from olfactory receptor neurons (ORNs) and does not rely on homophilic interactions.
• The related protein Tartan exhibits partial functional redundancy with Caps.

Conclusions:

• Leucine-rich repeat (LRR) transmembrane proteins, such as Caps and Tartan, play a crucial role in establishing the precise olfactory map.
• These LRR proteins likely function as part of a combinatorial cell-surface code that dictates glomerular targeting.
• This study elucidates a novel mechanism for neuronal wiring in the olfactory system.