The Cytoplasmic LIM Domain Protein Espinas Contributes to Photoreceptor Layer Selection in the Visual System.

Area of Science:

• Neuroscience
• Developmental Biology
• Molecular Biology

Background:

• Neuronal circuit assembly requires precise targeting of neurons to specific synaptic partners.
• Brain organization into layers and columns, as seen in the fly visual system, facilitates this process.
• The atypical-cadherin Flamingo (Fmi) and receptor Golden Goal (Gogo) were implicated in R8 photoreceptor layer selection.

Purpose of the Study:

• To investigate the role of Fmi intracellular signaling in R8 photoreceptor final layer selection.
• To determine the function of the LIM-domain protein Espinas (Esn) in R8 axon targeting.
• To elucidate the interaction between Fmi and Esn in neuronal wiring.

Main Methods:

• Analysis of R8 photoreceptor layer selection in esn mutants.
• fmi knockdown experiments in photoreceptors.
• Genetic interaction studies between fmi and esn.
• Demonstration of the necessity of the LIM domain for layer selection.

Main Results:

• esn mutants exhibit R8 axons overshooting their final target layer.
• fmi knockdown causes R8 axons to stall at the temporary layer, with some also projecting past the final layer.
• fmi and esn show a genetic interaction.
• The LIM domain of Esn is essential for R8 layer selection.

Conclusions:

• Fmi intracellular signaling is important for R8 final layer selection.
• Esn binds Fmi and cooperates in targeting.
• Esn likely signals downstream of Fmi to stabilize R8 axons in their final target layer, ensuring accurate circuit formation.