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The gene-editing tool CRISPR is moving into strange, new areas, as recently shown by a team in changing the colour of a butterfly’s wings.
We recently heard from Researchfest 2018 winner Eoin Murphy, who told us about the incredible power of CRISPR for the treatment of hereditary conditions such as Huntington’s disease. Now, the much-talked-about method is starting to make physical changes to living creatures.
In a paper published to Cell Reports, a team of researchers based in Singapore has revealed how, with a few modifications to pigment genes, it could change the colour and morphology of wing scales in squinting bushbrown butterflies.
“Our research indicates that the colour and structure of wing scales are intimately related because pigment molecules also affect the structure of scales,” said senior author Antónia Monteiro, a biologist at the National University of Singapore’s Faculty of Science and Yale-NUS College in Singapore.
“Some end-products of the melanin pathway, which produces butterfly wing pigments, play a role in both scale pigmentation and scale morphology.”
The African butterfly Bicyclus anynana wildtype form (left), with mutations in the melanin pathway seen in particular in the gene yellow (right). Image: William H Piel and Antónia Monteiro
Good news for biotech companies
To achieve this, the team disabled five of the butterfly’s pigment genes using CRISPR, but were surprised to find that this also resulted in the mutation of the wing scale structure.
When a mutation prevented the pigment dopa-melanin from being generated, an extra sheet of chitin – a fibrous component of the exoskeleton – formed horizontally on the upper surface of the wing scale. Also, when a different mutation blocked the pigment dopamin-melanin, vertical blades of chitin appeared.
Some butterflies are able to have vivid hues thanks to these thin layers of chitin on their scales as they interfere with the light to accentuate different colours. This is crucial to their survival as it helps them hide from potential predators, but is also useful when it comes to attracting a mate.
If the lab mutations were to occur naturally in the wild, it could spell their ultimate demise, but the team sees positives in the breakthrough.
“If we understand the developmental genetics of colour, biotech companies of the future might be able to generate vivid, brilliant colours via bioengineering, based on butterfly scales, instead of having to nanomanufacture them using metals, which is currently extremely difficult to do,” Monteiro said.
“These chitin-based colours would be lasting, biodegradable and environmentally friendly.”
