Abstract
Dscam2, a cell surface protein that mediates cellular repulsion, plays a crucial role in the development of the Drosophila melanogaster visual system. Dscam2 generates boundaries between neighboring modules in the fly optic lobe; in Dscam2 mutants this visual system modularity is compromised. Although developmental wiring defects have been well described in the Dscam2 mutant, behavioral consequences have not been investigated. To address this, we examined the visual behavior of Dscam2 mutant flies. Using a phototaxis assay, we ascertained that these flies are not blind, but have a reduced phototaxic response. Through population-based and single fly optomotor assays, we found that Dscam2 mutant flies can track motion but that their response is opposite to control flies under defined experimental conditions. In a fixation paradigm, which allows tethered flies to control the angular position of a visual stimulus, mutant flies' responses were diametrically opposed to those seen in control flies. These data suggest that modest changes in the modularity of the fly visual system in the Dscam2 mutant can dramatically change the perception of specific visual cues and modify behavior.
Highlights
The brain is the most complex organ in the human body as it utilizes an organized network of billions of neurons
The magnitude of the response in the mutants was significantly reduced compared to controls (Figure 2B). These results suggest that the circuitry that controls light detection is functional, but impaired, in the Down Syndrome Cell Adhesion Molecule 2 (Dscam2) mutants
We explored different visual behaviors in Dscam2 mutant flies
Summary
The brain is the most complex organ in the human body as it utilizes an organized network of billions of neurons. These neurons relay sensory information into actions and are the foundation of unique behaviors. In order to establish a functional connective network, neurons need to be able to discriminate and identify their own neurites and those of their neighboring cells. This discrimination is typically achieved through cell recognition molecules (CRMs) expressed on the plasma membrane. Each photoreceptor terminal makes ∼300 output synapses, each containing four postsynaptic elements two of which are invariantly lamina neurons L1 and L2
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