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Oca2 targeting using CRISPR/Cas9 in the Malawi cichlid Astatotilapia calliptera.

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Clark, Bethan 
Elkin, Joel 
Marconi, Aleksandra 
Turner, George F 
Smith, Alan M 


Identifying genetic loci underlying trait variation provides insights into the mechanisms of diversification, but demonstrating causality and characterizing the role of genetic loci requires testing candidate gene function, often in non-model species. Here we establish CRISPR/Cas9 editing in Astatotilapia calliptera, a generalist cichlid of the remarkably diverse Lake Malawi radiation. By targeting the gene oca2 required for melanin synthesis in other vertebrate species, we show efficient editing and germline transmission. Gene edits include indels in the coding region, probably a result of non-homologous end joining, and a large deletion in the 3' untranslated region due to homology-directed repair. We find that oca2 knock-out A. calliptera lack melanin, which may be useful for developmental imaging in embryos and studying colour pattern formation in adults. As A. calliptera resembles the presumed generalist ancestor of the Lake Malawi cichlids radiation, establishing genome editing in this species will facilitate investigating speciation, adaptation and trait diversification in this textbook radiation.



Organismal and evolutionary biology, Research articles, cichlids, CRISPR/Cas9, adaptive radiation, functional genetics, evo-devo

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R Soc Open Sci

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The Royal Society
Cancer Research UK (C13474/A18583, C6946/A14492)
Human Frontier Science Program (RGY0079/2018)
NSF (IOS-1825723)
Natural Environment Research Council (NE/R01504X/1)
Wellcome Trust (092096/Z/10/Z, 102175/Z/13/Z, 219475/Z/19/Z, 222279/Z/20/Z)