Christina MacLaren
chpage@bio.indiana.edu

Indiana University
Department of Biology
1001 E. 3rd Street
Bloomington, IN 47405 USA

Advisors:
Dr. Joe Duffy, Genetics, IU

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Research Interests

During the development of the fruitfly, Drosophila melanogaster, the Epidermal Growth Factor Receptor (EGFR) is involved in establishing polarity within the developing egg chamber.  In the latter stages of oogenesis, activation of EGFR signaling regulates dorsal patterning of the chorion, or eggshell.  One distinctive feature of this patterning event is the differentation of a pair of respiratory appendages, which mark the dorsal side of the egg chamber and appear to aid in gas exchange between the developing embryo and the outside environment.  While D. melanogaster has two such appendages, enormous diversity exists in both the number and morphology of these structures among species of the family Drosophilidae. We are interested in deciphering the molecular basis for this variation and the role, if any, of selection in dictating the diversity in appendage number and morphology. The role of EGFR in dorsal appendage patterning has been firmly documented in Drosophila melanogaster. Therefore, by investigating components of the EGFR pathway within a select group of Drosophilid species, I hope to determine whether variation in EGFR signaling dictates the diversity of chorion morphology in this family.

Among the components of EGFR signaling, several inhibitors of the receptor are especially interesting because of their unique regulatory role.  While vertebrates have four EGFR orthologues, as well as many activating ligands, no vertebrate orthologues of the inhibitory molecules found in invertebrates have been identified.  This suggests that invertebrates have evolved a distinct strategy for regulating EGFR activity.  What role do these inhibitory molecules play in appendage patterning in the Drosophilidae? An analysis of these molecules in various Drosophilid species should provide new information about their function, as well as insight into the evolution of EGFR inhibition.

In addition to mechanistic and evolutionary approaches to understanding the role of EGFR signaling in Drosophilid appendage patterning, a final component of this project addresses the potential role of Drosophilid ecology in driving the diversification of egg chamber morphology.  Are various appendage phenotypes specifically adapted to the oviposition substrate available to females of each species?  More specifically, has the evolution of EGFR inhibitory molecules in this family been shaped by such environmental constraints?  To fully understand the evolution of the EGFR signaling pathway in invertebrates, it is necessary to consider such adaptive explanations in conjunction with data from functional studies.  Addressing these questions in a small group of Drosophilids should provide a framework for understanding EGFR signaling and inhibition within the entire family and could potentially contribute to models of chorionic appendage patterning that currently rely only on data gathered from D. melanogaster.

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Publications

...none currently...