Thanks to new advances in genome editing, imaging, and single-cell sequencing, butterflies are powerful laboratory systems for tackling old and new questions in developmental biology. Their wing patterns are both simple, as 2D pixel arrays, and tremendously diverse, enabling unique insights into the evolution of development.   

Why to study the evo-devo of color patterns?

Color patterns are a form of spatial information that essentially results from a cascade of regulatory events taking place during wing development, including in the butterfly larvae, ie. well before wings are visible. Developmental patterning results in the complex compartmentization of the wing field into territories of cells that acquire final identities. The developing wing consists of a double-layer of epithelial cells, which will give rise to a an array of organized scales arranged in overlapping rows. Each color scale of the adult butterfly wing is secreted by a single cell. Thus, understanding color pattern formation consists in reverse engineering how a natural pixel screen is specifying fields of differentiated cells, reinforcing borders between them, and translating this regulatory identity into color (pigment-based or structural colors). ​

​We use CRISPR-Cas9 genome editing in butterflies to directly test the role of candidate developmental genes (signaling pathways, transcription factors) in the formation of two-dimensional color patterns.  This comparative research combines with gene expression studies, forward genetics, and ecological genomics to provide a comprehensive understanding of the origins of biodiversity. Butterflies are already well established model systems in Genomics,  Evolutionary Biology, and Ecology. Our overarching goal is to take a mechanistic lens on evolving morphologies and provide a more integrated understanding of genetic function, pattern formation, and phenotypic diversification.

WntA signaling is essential for pattern formation in nymphalids and beyond 

The WntA signaling ligand gene was originally mapped as locus of mimetic pattern variation in several Heliconius and Limenitis butterflies, and we then studied its outstanding effects in a multitude of species. WntA is a member of the metazoan Wnt family of ligands and appears to function as a morphogen in butterfly wings. 

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left: WT Vanessa cardui (ventral) middle: WntA CRISPR mosaic KO phenotype right: WntA expression in 17% pupal wings, at a stage where scale cell precursor have only started to differentiate

Expression in larval imaginal wing disks, and loss-of-function effects of WntA in the Gulf Fritillary butterfly (Agraulis incarnata)

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Mosaic knock-outs of canonical Wnt secretion factors porcupine and wntlesss/evi both phenocopy the WntA KO phenotypes. These data imply that WntA is processed and secreted similarly to traditional Wnt ligands.