Dscam2 affects visual perception in Drosophila melanogaster

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.

Location and functions of Inebriated in theDrosophilaeye

“…In phototactic experiments our wild-type flies preferred the blue-lit arm of the T-maze, as previously reported ( Jacob et al, 1977 ). However, Drosophila 's attraction to blue light has not always been observed and some studies report instead a green preference ( Bosch et al, 2016 ). Regardless, the phototactic responses of inebriated suggest that this mutant is not, in fact, blind.…”

Can You Hear Me Now?

“…A recent study showed that L4 neurons play a key role motion processing, resolving previous contradictory studies on its function (Meier et al, 2014). It was also found that visual circuit miswiring in the absence of Dscam2 leads to specific and conditional differences in visual acuity (Bosch et al, 2015). Strikingly, in three of the behavioral paradigms tested, Dscam2 mutants showed an opposing response as wild-type flies.…”

Analysing visual behaviour in Drosophila Dscam2 mutants using optimised optomotor and operant control assays

“…When a group of flies is placed in a tube and subjected to a moving grating perpendicular to the tube, the flies move against the direction of motion (Lee et al, 2001, Zhu & Frye, 2009; figure 1.2A/B). In contrast, populations of flies walking through an 8-tiered maze (figure 1.2C), single free walking flies in a paper/plastic striped drum (figure 1.2D) or tethered flies (figure 1.2E-F) move in the direction of the moving grating (Blondeau & Heisenberg, 1982, Bosch et al, 2015, Buchner, 1976, Evans et al, 2011, Götz, 1968, Götz & Wenking, 1973, Mccann & Macginitie, 1965, Van Swinderen & Flores, 2007. Why the optomotor response is assay-dependent is not known, and this thesis will provide new insight into this problem using both population and single fly assays.…”

“…Previous research demonstrated that in single choice population assays, a group of mixed gender flies walked in the opposite direction of the moving grating (Lee et al, 2001, Zhu & Frye, 2009. In the population assay described in this chapter, flies have to make a multitude of left/right choices while exposed to a moving grating and female flies respond by following the moving grating (Bosch et al, 2015, Evans et al, 2011, Van Swinderen & Flores, 2007.…”

“…To summarize, flies follow the direction of the moving stimulus in both assays described in this chapter (Bosch et al, 2015). These assays provide a foundation for studying motion detection in two different visual contexts and will be used in order to better understand the influence of gene manipulations on visual behaviours in Drosophila in chapter 4 and 6.…”