Aquaculture is growing to meet the needs of an increasing world population , and aquaculture genetics must move quickly to help producers meet the expectations of consumers and retailers. Genome Editing offers the opportunity to make targeted changes in the genome, introducing variation that will result in rapid and substantial improvements in performance, health and sustainability . T o responsibly introduce fish which harness the power of genetic technologies such as Genome Editing into commercial production systems, the farmed fish should be sterile or otherwise contained. The ability to produce sterile progeny from broodstock for aquaculture also has significant benefits to productivity and environmental sustainability. We describe the development of a strategy to generate, breed and mass-produce sterile fish.
Our strategy for mass producing sterile fish is designed to produce monosex, sterile populations. We first investigated gene mutations in two evolutionarily conserved pathways, one governing sex differentiation and the other sexual competency. We created edits in genes necessary for spermiogenesis and steroid hormone synthesis causing male sterility and masculinization, respectively. Double gene edit combinations for these genes produced all-male sterile populations. Likewise, we created variants in genes whose inactivation caused females to develop arrested or string-like ovaries lacking oocytes. We further disrupted genes causing genetic males to develop as females. Double gene edit combinations for these genes produced all-female, sterile populations.
Propagation of the double KO lines was achieved via germ cell transplantation from a juvenile edited donor into a germ cell free wild-type recipient embryo. In the resulting recipients, the induced edits had no effect as the genes targeted are not expressed in germ cells. With this approach, we generated fertile broodstock that successfully mass-produced sterile, monosex populations. We expect that adoption of this technology will result in broad economic and environmental benefits for aquaculture, and as a foundation upon which to build additional genetic technologies.