The cytoplasmic LIM domain protein Espinas contributes to photoreceptor layer selection in the visual system

Abstract

One of the central questions in neurobiology is how neurons discriminate between one another during circuit assembly. A common strategy of many nervous systems is the organization of brain regions in layers, to facilitate that neurons encounter a limited repertoire of synaptic partners. The fly visual system, which is structured in layers like many regions of the vertebrate brain, is used to identify cell surface molecules that mediate recognition between neurons and allow them to extend to specific layers. However, little is known about the intracellular pathways that link cell surface molecules to the cytoskeleton to determine whether or not to stabilize in a layer. Flamingo and its vertebrate homologs CELSR1/2 are cell surface molecules with widespread roles in neurite growth. In the fly visual system in particular, Flamingo regulates layer selection of a particular neuronal type. Our data suggests that in this context, Flamingo signals to the cytoskeleton through the conserved cytoplasmic molecule Espinas/PRICKLE2. Given that Flamingo and Espinas, as well as their respective vertebrate homologs, are broadly expressed in the nervous system, elucidating the interactions between them can reveal conserved mechanisms and provide valuable insights into the assembly of neural circuits.