Proof-of-concept for sterility induction in sablefish (Anoplopoma fimbria) via a scalable immersion-based gene silencing approach

Genetic introgression and loss of fitness in wild populations due to escape of farmed fish are major sustainability concerns in marine aquaculture. Induction of reproductive sterility in farmed fish is the most effective method for genetic containment and may confer other benefits. One promising approach, first developed in zebrafish, uses a Morpholino oligomer (MO) conjugated to a Vivo transporter to silence dead end (dnd), a key gene for germline development, without introduction of genetic modifications. Here, we describe the results of initial studies on this gene-silencing method with an emerging marine aquaculture species, sablefish (Anoplopoma fimbria). The deduced amino acid sequence for sablefish Dnd shared identities of 41–77 % with those of other teleost species. Tissue distribution analyses revealed robust and specific expression of dnd in gonads and unfertilized eggs. In hatchery trials, both pre- and post-fertilization treatment of eggs with dnd-MO-Vivo successfully induced sterility in some individuals (8 % and 4 %, respectively) and a transient ‘reduced germ cell’ phenotype was also observed (18 %). Gene expression analyses of key germ- and somatic-cell markers supported histological observations indicating an absence of germ cells in sterile gonads and accordance between the genotypic and phenotypic sex of sterile individuals. There were no differences in prepubertal plasma sex steroid levels between sterile and control fish or sexes. Our results further suggest that dnd-MO-Vivo treatment has minimal long-term consequences to fish performance. Future studies should focus on optimizing dnd-MO-Vivo concentrations and bath-immersion conditions to increase sterility rates.