In a scientific breakthrough, scientists have managed to modify the genes of cockroaches using CRISPR-Cas9, a technology with the ability to identify and alter parts of an organism’s DNA.
According to a study published by Cell Press on May 16, 2022 in the journal Cell Reports Methods, the simple and efficient technique, named “direct parental CRISPR (DIPA-CRISPR)”, involves the injection of materials into female adult cockroaches where eggs are developing rather than into the embryos themselves.
CRISPR is a simple yet powerful tool for editing genomes. It allows researchers to easily alter DNA sequences and modify gene function.
The achievement, which would have been relegated to science-fiction a few decades ago, produced the first so-called “knock-out cockroaches” and could be used to dramatically simplify gene-editing in numerous other insects, allowing for further exploration for applications in pest control, evolutionary biology and other entomological fields.
Dr Stephanie Morris, the programme director at the National Human Genome Research Institute, explains that “the term ‘knock-out gene’ refers to the use of genetic engineering to inactivate or remove one or more specific genes from an organism. Scientists create knock-out organisms to study the impact of removing a gene from an organism, which often allows them to then learn something about that gene’s function.”
Scientists have edited the genes of some insects by performing microinjection of CRISPR materials into embryos as they develop. However, the technique has been off limits to many species, including cockroaches, that, until now, have had inaccessible embryos.
“In a sense, insect researchers have been freed from the annoyance of egg injections,” says senior study author Takaaki Daimon of Kyoto University.
“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 successfully demonstrated that cockroach and beetle offspring contained artificially edited genes when their mothers were subjected to the injections, and that the “mutant” cockroach offspring also passed the artificial mutations onto the next generation after they mated.
“With over a million species described, insects are a treasure trove of diversity and represent boundless possibilities as research tools for answering fundamental questions in biology,” Shirai’s team said in the study.
“Current approaches for insect gene editing require microinjection of materials into early embryos, which is highly challenging in most species. In this work, we established and optimised a simple and efficient method for insect gene editing by adult injection, which can be readily implemented in any laboratory and directly applied to a great diversity of non-model insect species.”
According to the research report, scientists have struggled to apply CRISPR to cockroaches because the insects shield their fertilised eggs in hard cases for days or weeks until the offspring hatch. As a result of the “unique reproduction system, it is impracticable to inject materials into very early embryos” and so “genetic manipulation of cockroaches (that is transgenesis or gene editing) has not been achieved so far.”
Furthermore, the team of scientists discovered that when DIPA-CRISPR was applied to the red flour beetle, as much as 50% of the offspring inherited the mutant genes. The team also produced “knockin” beetles, meaning offspring that carried genes that were artificially inserted into their DNA, in contrast to knock-out organisms that carry artificially inactivated genes.
The findings lay the groundwork for future insect trials, which could provide fresh insights into the invertebrates; complex evolutionary histories as well as biosecurity applications.
“The successful application of DIPA-CRISPR in the two evolutionarily distant insect species gives an idea of its generalizability,” concluded Shirai’s team.
“Due to its simplicity and accessibility, DIPA-CRISPR will greatly extend the application of gene editing technology to a wide variety of model and non-model insects, including global/local agricultural and medical pests whose genomes have not been manipulated in any way.”