The gene ivory:mir-193 controls scale type differentiation in Heliconius butterflies

Hanly, J. J.; Camino, L.; Loh, L. S.; Livraghi, L.; Gilbert, L. E.; Wray, G. A.; Martin, A.; McMillan, W. O.; Holder, J. C.; Calderon-Onate, P.; Stroh, E. D.; Wagh, P. R.; Arias, C. F.; Ruiz-Moreira, J.; Zhao, L.

doi:10.64898/2026.02.24.707831

bioRxiv · 10.64898/2026.02.24.707831

The gene ivory:mir-193 controls scale type differentiation in Heliconius butterflies

Hanly, J. J.·Camino, L.·Loh, L. S.·Livraghi, L.·Gilbert, L. E.·Wray, G. A.·Martin, A.·McMillan, W. O.·Holder, J. C.·Calderon-Onate, P.·Stroh, E. D.·Wagh, P. R.·Arias, C. F.·Ruiz-Moreira, J.·Zhao, L.

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Abstract

The ivory:mir-193 locus is a genetic hotspot underlying melanic wing pattern variation across Lepidoptera, acting as a master regulator of melanic scale fate. This includes the genus Heliconius, where aposematic mimicry is driven by three scale cell types: light Type I, dark-melanic Type II, and red Type III scales. We tested functions of ivory:mir-193 in Heliconius using CRISPR-induced somatic mosaic knockouts of ivory and mir-193 across multiple pattern morphs. Knockouts converted Type II scales to Type I scales. Effects on Type III scales varied among and within individuals, indicating that ivory:mir-193 is permissive for Type III development. Using single-nucleus RNA-seq, we profiled the transcriptional landscape of H. melpomene-{Delta}78k mutants lacking mir-193. Loss of mir-193 produced readthrough transcription, consistent with a model where miR-193 acts as a co-transcriptional terminator. These data show that ivory drives wing pattern variation, while mir-193 mediates downstream diversity in scale fate across Lepidoptera.

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Hanly, J. J., Camino, L., Loh, L. S., Livraghi, L., Gilbert, L. E., Wray, G. A., Martin, A., McMillan, W. O., Holder, J. C., Calderon-Onate, P., Stroh, E. D., Wagh, P. R., Arias, C. F., Ruiz-Moreira, J., Zhao, L.. 2026-02-26. The gene ivory:mir-193 controls scale type differentiation in Heliconius butterflies. https://doi.org/10.64898/2026.02.24.707831

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