CRISPR cartoon in cockroaches. Credit: Shirai et al./Cell report methods
Researchers have developed a CRISPR-Cas9 approach to enable gene editing in cockroaches, according to a study published by Cell Press May 16 in the journal Cell report methods. The simple and effective technique, dubbed “direct parental” CRISPR (DIPA-CRISPR), involves injecting materials into the adult females where the eggs are developing rather than into the embryos themselves.
“In a sense, insect researchers have been freed from the embarrassment of egg injections,” says the study’s lead author, Takaaki Daimon, of Kyoto University. “We can now modify insect genomes more freely and at will. In principle, this method should work for more than 90% of insect species.”
Current insect gene-editing approaches typically require microinjection of materials into early embryos, severely limiting its application to many species. For example, previous studies have failed to genetically manipulate cockroaches due to their unique reproductive system. Moreover, insect gene editing often requires expensive equipment, species-specific experimental setup, and highly trained laboratory personnel. “These problems with conventional methods have plagued researchers who want to perform genome editing on a wide variety of insect species,” says Daimon.
To overcome these limitations, Daimon and collaborators injected Cas9 ribonucleoproteins (RNPs) into the main body cavity of adult female cockroaches to introduce inherited mutations into developing eggs. The results demonstrated that the efficiency of gene editing – the proportion of edited individuals out of the total number of hatched individuals – could be as high as 22%. In the red flour beetle, DIPA-CRISPR achieved an efficiency of more than 50%. Additionally, researchers have generated beetle knockin genes by co-injecting single-stranded oligonucleotides and Cas9 RNPs, but the efficiency is low and needs further improvement.
The successful application of DIPA-CRISPR in two evolutionarily distant species demonstrates its potential for large-scale use. But the approach is not directly applicable to all insect species, including fruit flies. Additionally, experiments have shown that the most critical parameter for success is the stage of adult females injected. Therefore, DIPA-CRISPR requires a good knowledge of ovarian development. This can be difficult in some species, given the various life cycles and reproductive strategies of insects.
Despite these limitations, DIPA-CRISPR is accessible, highly practical, and could be easily implemented in laboratories, extending the application of gene editing to a wide diversity of model and non-model insect species. The technique requires minimal equipment for injection in adults, and only two components – Cas9 protein and single guide RNA – greatly simplifying gene editing procedures. Additionally, standard commercially available Cas9 can be used for adult injection, eliminating the need for time-consuming custom engineering of the protein.
“By improving the DIPA-CRISPR method and making it even more efficient and versatile, we may be able to enable genome editing in nearly all of the more than 1.5 million insect species, opening up a future in which we will be able to fully utilize the incredible biological functions of insects,” says Daimon. “In principle, it is also possible that the genome of other arthropods can be modified using a similar approach. These include agricultural and medical pests such as mites and ticks, and important fish resources such as shrimp and crabs.”
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Takaaki Daimon, DIPA-CRISPR is a simple and accessible method for insect gene editing, Cell report methods (2022). DOI: 10.1016/j.crmeth.2022.100215. www.cell.com/cell-reports-meth … 2667-2375(22)00078-9
Quote: CRISPR now possible in cockroaches (May 16, 2022) retrieved May 17, 2022 from https://phys.org/news/2022-05-crispr-cockroaches.html
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