Transgenic approaches for the reproductive containment of genetically engineered fish

Aquacultural applications of transgenic technologies have the potential to supply the ever growing demand for food products derived from aquatic resources. However, before any benefits of genetically engineered fish can be realized, methods for the containment of transgenic fish must be developed to help prevent their interbreeding with native populations should they be accidentally released or escape. In this review, the current methods of physical and biological containment in use by aquaculturists for confinement of domestic farmed fish are outlined and discussed with regard to their applicability and effectiveness for the containment of transgenic fish. New and developing transgenic approaches for the confinement of genetically engineered fish, including transgenic sterilization, disruption of embryonic development, and gonad-specific transgene excision are then discussed in detail. Although some preliminary studies allude to ongoing experiments, there are few peer-reviewed scientific publications that describe the implementation of these techniques. The current dearth of publications demonstrating the success of these technically complex methods, even in model fish species, suggests that difficulties may be prevalent when trying to implement such transgenic containment approaches in vivo. Although these containment approaches are being developed to reduce the risks arising from released or escaped transgenic fish, these containment transgenes must themselves survive regulatory scrutiny. Given the extensive regulatory review process that has been associated with the approval of genetically engineered organisms expressing well-characterized proteins that have historically been present in the food supply and are generally regarded as safe, transgenic containment approaches using novel proteins may face an even longer and more complex regulatory process. Nuclear transfer cloning of cultured somatic cells has been reported for model fish species, and represents a non-transgenic approach for the production of targeted gene knockouts in commercial fish species. Inactivating key reproductive gene(s) such that fertility restoration can only be achieved by the selective administration of exogenous hormones may offer an effective solution for the reproductive containment of transgenic fish. Considering the need for dependable containment of transgenic fish and the technical and regulatory challenges that may be associated with transgenic containment approaches, future developments in gene knockout technology may ultimately result in a more reliable and commercially viable approach to achieve genetic reproductive containment. (c) 2008 Elsevier B.V All rights reserved.