Researchers have found a simpler way to genetically modify cockroaches with CRISPR-Cas9, considerably reducing the time needed to conduct insect research.
CRISPR-Cas9 is a molecule first discovered in bacteria, which has made genetic modification a much faster and more efficient process.
The new technique, called direct parental CRISPR, or DIPA-CRISPR, allows researchers to avoid having to microinject CRISPR materials into insect embryos. Apparently, this is a major inconvenience in the genetically modified insect world, and it doesn’t work for every insect. In fact, cockroaches’ odd reproductive systems prevent them from being genetically modified with embryo microinjections.
Instead, DIPA-CRISPR works by a female cockroach being injected with the relevant CRISPR tools – meaning that some of her offspring carry the induced genetic modifications.
“In a sense, insect researchers have been freed from the annoyance of egg injections,” says Takaaki Daimon, a researcher at Kyoto University, Japan, and senior author of a paper describing the research, which has been published in Cell Reports Methods.
“We can now edit insect genomes more freely and at will. In principle, this method should work for more than 90% of insect species.”
The researchers used commercially available Cas9 ribonucleoproteins (the proteins that induce genetic modification) to test this method.
They injected these ribonucleoproteins into the haemocoels (main body cavity) of two different insects: the German cockroach (Blattella germanica), and the red flour beetle (Tribolium castaneum).
They then investigated the offspring of these insects, to see whether their genetic modification had worked.
The Cas9 proteins that were designed to “knockout” genes (that is, remove a gene from a genome) were very successful, by genetic modification standards. More than 50% of the red flour beetle offspring, and 22% of the cockroach offspring, lacked the pigment-creating gene that the researchers wanted to remove.
“Knockin” modifications (introducing a new gene into the genome) were less successful, with only very low efficiency.
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The technique depends on the reproductive stage the adult females are at, and a strong understanding of the insect’s ovary development. Unfortunately, fruit flies – which are a model organism for lots of genetic research – won’t respond to this technique.
Nevertheless, the researchers say that DIPA-CRISPR will reduce the expense, and timeframes, of a lot of insect research.
“By improving the DIPA-CRISPR method and making it even more efficient and versatile, we may be able to enable genome editing in almost all of the more than 1.5 million species of insects, opening up a future in which we can fully utilise the amazing biological functions of insects,” says Daimon.
“In principle, it may be also possible that other arthropods could be genome edited using a similar approach. These include agricultural and medical pests such as mites and ticks, and important fishery resources such as shrimp and crabs.”
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