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Scientists have created a guide to gene editing

Researchers working on understanding the genetic mechanisms that affect how salmon become resistant to lice wrote a guide that helps assess the risks of gene editing.

Gene editing applications will have a consequential web of potential benefits and harms with associated risks affecting all levels of aquaculture value chains, aquatic ecosystems, and society. The same principles apply to the aquaculture of all aquatic organisms. Large solid lines indicate the main areas requiring careful consideration and assessment: mechanisms for creating and disseminating gene-edited food; phenotypic effects on the animal under production; positive or negative impacts (on production, local ecosystems, global effects, and food products), and ethical business practices. Public perceptions will be influenced by having good transparency and continuous dialogue about the risks and the benefits assessed for each gene editing application. Created with BioRender.com.

Nick Robinson is from Australia and works as a senior researcher at Nofimain Norway, and has just sat down in his chair in an office in Scotland. The office belongs to Diego Robledo, who is from Spain, but he is a researcher at the Roslin Institute at the University of Edinburgh. They are two of the researchers behind the guide they have created in the CrispResist project. But first a little about the project's main work:

"We are trying to map the genetic mechanisms that make the Pacific salmon resistant to lice", says Robinson in a press release.

Lice and salmon

Salmon lice feed on skin and blood, and the salmon become ill. Salmon lice are a problem for both fish welfare and the industry. But there are salmon that do well against salmon lice:

"In wild silver salmon, this happens naturally. The cells of the salmon surround the lice and kill them", explains Diego Robledo.

Both silver salmon and humpback salmon are two species of salmon that live in the Pacific Ocean. They fight salmon lice naturally in a way that the Atlantic salmon - the salmon we know from Norwegian rivers and farms - cannot.

Welfare and survival

Our genome research helps scientists understand which genes are involved in making Pacific salmon resistant to salmon lice. The next step in the project is to use gene editing to test the function of these genes in Atlantic salmon. Early next year, the researchers are ready to test gene-edited salmon together with lice in a closed, biosecure facility.

"We will see if small changes in the genes cause the salmon's immune cells to encapsulate the lice and kill them, in the same way as in silver salmon, or prevent them from attaching, as in humpback salmon", says Nick Robinson.

He emphasizes that there is no question of the project editing genes in fish that will be reared in the sea for sale. The researchers will only test which genes affect the salmon's ability to resist lice infestation. They will look at what happens exactly where the lice attach to the salmon, and what role the genes play in stopping the lice.

"This could have great advantages in the future, if it is possible to use the knowledge we build in the project to produce a resistant salmon, says Robinson. The researcher goes on to say that lice create wounds that become infected. If the researchers can help the salmon to become resistant to lice, it has major benefits for fish welfare.

"By potentially changing the entire epidemiology of lice infection in the farms, it will also be possible to reduce the lice pressure in wild salmon", he says.

The salmon lice also have a greater preference for Atlantic salmon than other salmon species, such as humpback salmon. If the researchers manage to find out why this is the case, it could help the salmon to become more resistant to salmon lice.

Risks and benefits of gene editing

In the project, the researchers will edit the genes that their research indicates can keep the salmon lice-free and healthy. But is gene editing safe to use on salmon to be farmed and sold?

"It must be thoroughly evaluated how the editing can affect the health and welfare of the fish, the ecosystem in the sea and society in general. Thus, consumers and other interest groups must also be involved in the decision-making process. The benefits should be weighed against potential negative effects", says Robledo.

That is why Robinson and Robledo have written a guide together with partners in Nofima, the University of Edinburgh and Deakin University in Australia (A guide to assess the use of gene editing in aquaculture a>) which helps to map the risks of gene editing.

The gene editing project Robinson and Robledo are leading has brought together a large group of leading scientists from around the world - here they are at the Roslin Institute in Edinburgh. Photo: NOFIMA

"The guide was written to help assess risks and benefits, so that you can make informed decisions, says Robledo. - It addresses issues such as how the genes are edited, how gene editing can be made part of a research programme, how wild species can be affected, society's views on the method, the benefits for animal health and welfare, ecology, environmental footprint, human nutrition and local communities.

"The changes we make are quite small. We don't use genes from other animals, we make small adjustments to the genes the salmon already have", explains Robinson.

Pigs and cucumber

Their guide to gene editing can probably be applied to other fish species, animals and plants. - We focus on the farming industry, but the guidance is just as relevant for other species, says Robledo. - The questions to ask are the same for livestock and plants. We have not seen similar guidance relating to gene editing risk assessments published or proposed for other species used in food production, says Robinson.

The researchers emphasize that gene editing should not replace normal breeding, where individuals with the best genetic variants for the characteristics you are looking for are selected, and bred on these in favorable combinations in order to transfer the best genetic variants to the next generation.

CrispResist

This research is part of the CrispResist project. The aim of the project is to find out which genes are responsible for why salmon species such as silver salmon and humpback salmon are less susceptible to lice than Atlantic salmon. Atlantic salmon is the species used most for fish farming around the world. The project uses the gene editing method CRISPR-Cas9 to test the function of various genes.

Nick Robinson, senior researcher at Nofima, is the project manager, together with partners from Norway, Sweden, the UK, Canada, the USA and Australia.

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