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SUMMARY:Colour vision in flies - Professor Claude Desplan\, Department of 
 Biology\, New York University\, USA
DTSTART:20090611T103000Z
DTEND:20090611T113000Z
UID:TALK18674@talks.cam.ac.uk
CONTACT:14258
DESCRIPTION:Abstract: The Drosophila compound eye is made of 800 unit eyes
  (ommatidia) that each contains eight photoreceptors: Six are involved in 
 motion detection while two (R7 and R8) play a major role in color vision. 
 These ommatidia can be grouped into four categories: p ommatidia contain U
 V-sensitive Rh3 in photoreceptors R7 and Blue-Rh5 in R8 while y ommatidia 
 express another UV-Rh4 in R7 and green-Rh6 in R8. The p and y subsets are 
 distributed stochastically throughout the retina in a 30:70 ratio. Compari
 son between the inputs of R7 and R8\, and between p and y ommatidia allows
  flies to discriminate between colors\, with p ommatidia involved in the d
 etection of short wavelengths and y ommatidia for longer wavelengths. Dors
 al Rim Area (DRA) ommatidia express UV-Rh3 in both R7 and R8. They functio
 n as polarizing filters that allow the fly to measure the vector of light 
 polarization for navigation on cloudy days. A fourth subset located in the
  dorsal third of the eye co-expresses UV-Rh3 and -Rh4 in yR7 and serves to
  detect solar vs. anti-solar orientations\, also for navigation on sunny d
 ays. \n\nI will describe the cascade of genes that specify the different s
 ubsets of photoreceptors through a series of fate restrictions and how thi
 s cascade is modified to define the various regions of the retina in Droso
 phila and how this spatial organization is used in other insect species: h
 omothorax is required for the formation of the DRA. spineless is expressed
  in a stochastic manner in R7 cells that express Rh4 (yR7).  It allows the
  specification of the whole retina by specifying the y choice in R7 and al
 lowing R7 to instruct R8 of its choice. Finally\, IroC genes determine the
  region where yR7 co-express Rh3 and Rh4. \nProcessing of color informatio
 n occurs in the medulla that receives input from R7 and R8. The medulla is
  formed by approximatly 40\,000 neurons surrounding a neuropil where photo
 receptors and medulla neurons interconnect. Associated with each set of R7
 /R8 projections\, there are approximatly 800 ‘columns’\, the functiona
 l units in the medulla. We are addressing how medulla cells process color 
 information coming from R7 (sensitive to UV) and R8 (sensitive to blue or 
 green) and send it to higher processing centers in the lobula complex and 
 central brain to mediate color behavior. \n\nWe are silencing subsets of m
 edulla neurons using specific Gal4 lines and testing the consequence for c
 olor discrimination. We have adapted to color vision the flight simulator 
 originally designed by the Dickinson/Frye labs. In an operant paradigm\, t
 he fly is trained to associate color with a reward or punishment before be
 ing tested in the absence of the reward.\n\nBiosketch: Dr Desplan was trai
 ned at the Ecole Normale Superieure in St Cloud\, France where he obtained
  the ‘agregation’ in 1975.  He did his PhD in Paris at the INSERM with
  Drs. Moukhtar and Thomasset on Calcium regulation before joining Pat O’
 Farrell’s lab at UCSF. This is where he initiated his studies of the hom
 eodomain and demonstrated that this conserved signature of many developmen
 tal genes was a DNA binding motif. In 1987\, he joined the Faculty of Rock
 efeller University and was a Howard Hughes investigator.  He pursued struc
 tural studies of the homeodomain and initiated his work on the evolution o
 f axis formation in insects. In 1997\, he embarked into the investigation 
 of color vision in Drosophila that occupies most of his current laboratory
 . He moved as a professor to New York University in 1999.  His team has de
 scribed the molecular mechanisms of patterning of the fly retina that unde
 rlies color vision. He is now studying processing of color vision with an 
 investigation of the functional anatomy of the medulla part of the optic l
 obe. In parallel\, his lab developed the wasp Nasonia as a model system to
  compare early developmental events in the embryo (Evo-Devo). He contribut
 ed extensively to the understanding of how insect embryos pattern their an
 tero-posterior axis through the utilization of many of the same genes that
  are used in Drosophila with significant changes in the network\, in parti
 cular through mRNA localization.\n\nURL: http://www.nyu.edu/projects/despl
 an
LOCATION:Biochemistry Lecture Theatre\, Gurdon Institute\, Tennis Court Ro
 ad\, Cambridge
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