Activation of butterfly eyespots by Distal-less is consistent with a reaction-diffusion process

Area of Science:

• Developmental biology
• Genetics
• Evolutionary biology

Background:

• Eyespots in nymphalid butterflies are key models for pattern formation.
• The precise role of Distal-less (Dll) in eyespot development remains debated.

Purpose of the Study:

• To investigate the function of Distal-less (Dll) in butterfly eyespot development using CRISPR-Cas9.
• To understand how specific mutations in Dll affect eyespot formation and other wing phenotypes.

Main Methods:

• CRISPR-Cas9 gene editing in *Bicyclus anynana* butterflies.
• Analysis of phenotypic outcomes based on targeted Dll exons.
• Reaction-diffusion modeling of Dll, Wnt, and Dpp interactions.

Main Results:

• CRISPR mutations in Dll exon 2 caused missing/ectopic eyespots and exon skipping.
• Mutations in Dll exon 3 resulted in null phenotypes like missing eyespots and scale loss.
• Reaction-diffusion models accurately replicated observed crispant phenotypes.

Conclusions:

• Dll acts as an activator in eyespot development, scale growth, and melanization.
• Modulating Dll expression levels can generate diverse eyespot patterns.
• This study provides mechanistic insights into butterfly wing pattern evolution.