- Columbia University. PhD.
- The Warts/melted bistable loop ensures that the decision in R8 to express Rh5 or Rh6 is robust. However, we have shown that the presence of a functional Rh6 protein is also required to maintain exclusion of Rh5 from yR8 photoreceptors. In rh6 mutants these photoreceptors are specified correctly, and Rh5 expression is initially restricted to the p R8s. However, as the fly ages without Rh6 activity, yR8s also start to express Rh5, suggesting that Rh6 is required to maintain repression of the rh5 gene. We are investigating the involvement of the phototransduction cascade and developmental mechanisms in this pathway and are also screening for other genes that function to maintain exclusive Rhodopsin expression in the fly photoreceptors.
Sensory systems with high discriminatory power use neurons that express single sensory receptor genes from a battery of alternatives. In the normal fly retina (left panel), 70% of R8 color photoreceptor neurons express green light-sensitive Rhodopsin 6 (Rh6, stained in red) and 30% express blue-sensitive Rh5 (stained in blue). In frank sinatra mutants (right panel) part of the rh6 promoter is deleted reducing Rh6 expression to only a few cells. As a consequence, Rh5 becomes de-repressed in almost all R8s in an aging fly. Thus, Rh6 is not only a light receptor which initiates the phototransduction cascade but also acts to maintain the repression of the alternative rhodopsin gene. This preserves exclusive Rh5/Rh6 expression pattern and represents a striking example of one sensory receptor maintaining repression of the alternative sensory receptor. (Green counterstain labels light-gathering structures of all photoreceptors.)
- Ruth L. Kirschstein National Research Service Award (Postdoctoral Fellowship)