Pattern Formation and Eyespot Determination in Butterfly Wings

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The color patterns of butterfly wings are some of the most spectacular examples of pattern formation in cellular fields. Little is known, however, about how these patterns develop and evolve. Recently, a molecular characterization of butterfly wing pattern formation was initiated by cloning butterfly homologs of numerous Drosophila appendage- patterning genes. The expression of these genes in developing imaginal discs indicates that while the overall organization of the developing butterfly wing is similar to that of Drosophila, the suborganization of the butterfly wing is marked by novel and dynamic patterns of regulatory gene expression, some of which presage the future position of adult wing pattern elements. The project proposed here aims to test three hypotheses emanating from this initial characterization of the patterning landscape in butterfly wings, including: (1) eyespot formation is the product of a genetic circuit involving proximodistal patterning genes; (2) the secreted wingless, decapentaplegic and hedgehog signaling proteins are involved in wing pattern formation; and (3) the developmental prepattern may be conserved and its interpretation by downstream genes is species-specific. The experimental plan involves the cloning of several additional proximodistal patterning genes, the analysis of their spatial and temporal relationships throughout wing formation, assessment of individual protein functions through ectopic expression studies, and the comparative analysis of developmental prepatterns in different butterfly species. The combination of descriptive, experimental, and comparative work is aimed at identifying some of the principal mechanisms guiding the development and evolution of wing patterns.