Functional Studies in Atlantic Salmon (Salmo salar L.) Reveals Candidates for Sterility Vaccines

Recent biotechnological innovations such as the CRISPR-Cas9 methodology, have allowed applying genetic engineering approaches also to non-model organisms, including studies on gene function in Atlantic salmon. We have explored this methodology with the aim to target one of the major sustainability problems in salmon aquaculture: sexually mature escapees. Genetic introgression into wild populations is currently one of the factors limiting the expansion of the Norwegian salmon industry. To address this problem, we are investigating the possibility to induce sterility by vaccination against factors mediating germ cell survival in salmon. We have used CRISPR-Cas9 technology to elucidate the function of candidate genes in germ cell survival. Due to the long generation time of salmon we chose to analyze complete loss of function in F0. To avoid analysis of mosaic individuals, we simultaneously induced CRISPR-Cas9-mediated mutations in the albino (alb) and in the target gene. We observed that complete loss of pigmentation indicated bi-allelic disruption of alb but also of the second gene that was targeted. This methodology allowed producing germ cell-free salmon in F0. Different from medaka and zebrafish but similar to the loach, male and female somatic sex differentiation of the somatic gonadal elements did take place in germ cell-free salmon. We are also now following growth in germ cell free fish to evaluate if this type of sterility is suitable for the aquaculture industry. In addition we are at this time investigating a sterility vaccine using this target.