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Jan 22, 2017

Sterile salmon headline genetic event

A project that has successfully created sterile salmon by mutating genes responsible for germ cell development in fish larvae was one of the highlights of the first day of Aquaculture Europe 2016. The event, which is taking place in Edinburgh this week, featured a large session on applying genetic and genomic techniques in aquaculture research. Contributing to the session included using genetic profiling to assess fish health parameters such as temperature sensitivity, disease resistance and stress responses; determining growth related signatures to improve cultured Pacific bluefin tuna broodstock; or assessing the effects that plant-based diets have on growth rates. However, one particularly pressing issue plaguing commercial aquaculture is the effect of escapees on the genetic diversity of wild populations. But a team of researchers at the Institute of Marine Research (IMR) in Bergen Norway is getting closer to helping solve this problem. Genetic engineering shows tremendous potential Called “Salmosterile”, the project aims to develop a molecular method to induce sterility in salmon. Presenting the research, Dr Lene Kleppe, a post doctoral research at IMR, explained how sterility can be induced by mutating genes (survival factors) responsible for germ cell (ovary or testes) development in fish larvae. As Kleppe explained, the potential interbreeding and reduction in genetic diversity by escapees is one of the major bottlenecks in expansion of salmon aquaculture. Additionally, precocious puberty (early onset of sexual maturation) presents a problem for the industry as this results in reduced filet quality, reduced growth and decreased immunocompetence. Current methods to induce sterility include using pressure to produce triploid eggs – however, these fish are often sensitive to suboptimal conditions including increased temperature. Therefore, the group is trying to develop another method using state-of-the-art genetic techniques that might produce a more robust sterile fish. One technique uses an extremely precise way of genetic modification, called CRISPR/cas9 – which is basically a way of editing a gene by changing up to a single nucleotide (analogous to erasing one letter in a book). First the researchers identified 200 genes specifically expressed by the gonads of salmon. Then using the CRISPR/cas9 system, they looked at whether knocking out that gene will render the fish sterile. And so far, the results look very promising. Knocking out the ‘dead end‘ gene, the team has been able to induce sterility in salmon – mutant fish had no ovary tissues and there was no expression of germ cell markers. The research team is also looking at developing a vaccine that would result in sterility. Preliminary results for this technique are very promising. Read the article.