Sustainable use of CRISPR/Cas in fish aquaculture: the biosafety perspective

Abstract

Aquaculture is becoming the primary source of seafood for human diets, and farmed fish aquaculture is one of its fastest growing sectors. The industry currently faces several challenges including infectious and parasitic diseases, reduced viability, fertility reduction, slow growth, escapee fish and environmental pollution. The commercialization of the growth-enhanced AquAdvantage salmon and the CRISPR/Cas9-developed tilapia (Oreochromis niloticus) proffers genetic engineering and genome editing tools, e.g. CRISPR/Cas, as potential solutions to these challenges. Future traits being developed in different fish species include disease resistance, sterility, and enhanced growth. Despite these notable advances, off-target effect and non-clarification of trait-related genes among other technical challenges hinder full realization of CRISPR/Cas potentials in fish breeding. In addition, current regulatory and risk assessment frameworks are not fit-for purpose regarding the challenges of CRISPR/Cas notwithstanding that public and regulatory acceptance are key to commercialization of products of the new technology. In this study, we discuss how CRISPR/Cas can be used to overcome some of these limitations focusing on diseases and environmental release in farmed fish aquaculture. We further present technical limitations, regulatory and risk assessment challenges of the use of CRISPR/Cas, and proffer research strategies that will provide much-needed data for regulatory decisions, risk assessments, increased public awareness and sustainable applications of CRISPR/Cas in fish aquaculture with emphasis on Atlantic salmon (Salmo salar) breeding.

CRISPR/Cas Genome Editing—Can It Become a Game Changer in Future Fisheries Sector?

“…The CRISPR/Cas9 genome editing technology holds a great promise for disease control and molecular breeding in aquaculture. Unlike traditional transgenesis, which involves the transfer of a gene from one organism to other concerning the public safety regulations of genetically modified organisms, CRISPR/Cas genome editing allows specific, targeted, and often minor changes to the genome of the species of interest, and it does not introduce any foreign DNA, thereby alleviating major public concerns on the safety of GMOs (Okoli et al, 2021). The provision of the in vitro synthesis of sgRNA allows for multiplex CRISPR/ Cas9 for editing at multiple sites on the targeted gene and also for the higher probability of a gene knockout event.…”

“…To induce heritable modifications through gene editing, it must happen very early in the development, ideally at the onecell stage so that they can be incorporated in its germ line, hence the need for specialized methods like microinjection to deliver the CRISPR/Cas complex on a microscopic scale. Nevertheless, other procedures to deliver the CRISPR/Cas9 complex into one-cell fertilized eggs or cultured cell are lentivirus-mediated methods, electroporation, and ribonucleoprotein complexes (Okoli et al, 2021;Yang et al, 2022). Mutants should be carefully screened using sequence analysis, and off-target affects should be assessed.…”

“…-The egg membrane makes a low microinjection success rate for oviparous fish, and in ovoviviparous fishes, there is no established gene editing platform at present. Moreover, in some fish species, the egg membrane/shell is soft and in some species, it is very hard (e.g., tilapia), so the standardization of the needle type and injection is essential (Okoli et al, 2021).…”

“…Government regulation and public acceptance are the greatest challenge for CRISPR/Cas genome editing in aquaculture. The CRISPR technology has the potential to improve aquaculture production; however, public and regulatory acceptance are the key to its potential being realized (Okoli et al, 2021). CRISPR/ Cas-editing applications remain mostly at the research stage, and in aquaculture breeding programs, it is still limited.…”

Advantages, Factors, Obstacles, Potential Solutions, and Recent Advances of Fish Germ Cell Transplantation for Aquaculture—A Practical Review

“…Second, genetic containment can be accomplished with sterile fish that prevent polluting wild populations’ genetic pool when selectively bred or even genetically modified farmed fish escape. Especially, sterilization is vital for containing transgenics and genome-edited mutants for their commercial applications [ 184 , 185 ]. Third, sterility is a means for producers to protect valuable strains from unauthorized propagation and unexpected technological leakages.…”