Since the Nobel Prize in Chemistry was awarded to biochemist Jennifer Doudna and microbiologist Emmanuelle Charpentier in 2020, for developing the gene-editing technique known as Crispr-Cas9, Crispr has garnered a lot of attention and interest from scientists. The technique has been touted as a possible source of new treatments for diseases caused by genetic mutations, such as muscular dystrophy and congenital blindness. According to Science Dailyscientists were able to perform gene editing on cockroaches using the Crispr technique.
What is Crispr?
crisp is the abbreviation of small palindromes grouped regularly spaced. The technique has been described as “molecular scissors” that allow geneticists and medical scientists to edit genes by removing, adding or altering sections of DNA. The technique is easy to use, leading many scientists to believe that new applications will be easily found. It is the simplest, most precise and most versatile gene-editing technique available.
What did the scientists do with it?
A recently published article explains that scientists have been able to use Crispr to edit insect genomes to help scientists answer fundamental questions about biology. Previously, gene editing was done by microinjecting materials into the insect’s earliest embryos. Additionally, embryo injection must take place between spawning and the preblastoderm stage, which does not apply to species that give birth instead of spawning, or to species whose embryos are difficult to access at first. , like cockroaches.
This makes it very difficult when it comes to insects. The scientists used “direct parental” Crispr (DIPA-CRISPR) to allow them to inject adult females with Cas9 ribonucleoproteins (RNPs) into their haemocoel, effectively introducing inherited mutations into developing oocytes.
Source: Direct Science
The scientists also discovered that it is possible to use the commercially available standard Cas9 protein which can be directly used for DIPA-CRISPR. This makes this solution widely applicable. DIPA-CRISPR is important because it enables very efficient gene editing in cockroaches. This discovery means the technique can be used among a wider range of insects.
Pre-injecting eggs was very difficult and time-consuming, while this much simpler method will allow scientists to edit the genes of more than 90% of insects out of the 1.5 million insect species in the world .
In the past, with microinjections, progress in gene editing was very slow. Indeed, genetic manipulation was impossible due to the nature of an insect’s reproductive system. Insect gene editing is very expensive to perform because it requires a lot of specific equipment and is more technically demanding.
By injecting Cas9 RNPs into the main body cavity of the adult female cockroach to introduce mutations into the DNA of developing eggs, scientists have found that gene editing efficiency can be as high as 22%. Gene editing efficiency refers to the share of edited individuals in the group of hatched individuals. Red flour beetles were 50% effective with DIPA-CRISPR. Additionally, scientists were able to create genetic knockin beetles through the co-injection of single-stranded oligonucleotides (ssODNS) and Cas9 RNP. This demonstrates the generalizability of the use of DIPA-CRISPR. There is no need to customize Cas9 or use special reagents to facilitate absorption from the ovaries. DIPA-CRISPR is therefore potentially a much simpler, much cheaper and much more versatile solution, usable in most laboratories, and therefore usable in all laboratories. most insect species.
Limits of the technique
While the benefits of DIPA-CRISPR are vast, it is also true that it requires in-depth knowledge of the development of the ovaries in the target species, since Cas RNPs use vitellogenesis to be able to be internalized into the oocyte. The staging of vitellogenic females is therefore potentially very important. Not only is this crucial, but it is also difficult to do given the different insect life cycles and reproductive strategies.
DIPA-CRSIPR cannot be used for species for which oogenesis occurs without perceptible vitellogenesis, such as aphids during parthenogenetic reproduction. This is the case with fruit flies such as Drosophila melanogaster and certain higher Diptera. In addition, D. melanogaster has a very limited temporal and spatial range permeability compared to other species.
DIPA-CRISPR has a wide range of potential advantages: namely, it is widely generalizable, it is cost-effective and has lower technical requirements, making it usable in most laboratories. Therefore, scientists can expect to edit the genes of a wider range of insect species.
DIPA-CRSIPR only requires Cas9 RNAs, which simplifies gene editing. Additionally, commercially available Cas9 can be injected into adult insects, so custom engineering of Cas9 is no longer necessary.
It is a unique achievement to open the door to gene editing of over 1.5 million species of insects, especially considering the difficulties that gene editing has endured in the past. As a result, fundamental biological questions can be asked by scientists. In addition; the technique makes it possible to imagine gene editing of other arthropods, such as mites and ticks and other agricultural and medical pests, and fishery resources such as crabs and shrimps, using the DIPA-CRISPR technique.