Antisense and ribozyme constructs in transgenic animals

Geneticists have long sought the ability to add or subtract individual genes from an organism's genome, or to be able to alter the level of expression of a gene in a targeted, developmentally and tissue-specific manner. The development of transgenic technology realized the possibilities of increasing the expression of a specific gene or the transfer of a new gene into an animal. Homologous recombination techniques allow the deletion or alteration of a gene in vivo. The production of transgenic animals incorporating a gene construct that expresses a complimentary antisense RNA to a targeted gene, or an antisense RNA incorporating a catalytic, ribozyme sequence, have been suggested as a potential mechanism for obtaining the developmentally and tissue-specific down-regulation of expression of a targeted gene in vivo. In this paper we review the current literature with respect to the application of antisense and ribozyme constructs in transgenic animals and conclude that such constructs can effectively downregulate the level of mRNA from a target gene, the amount of protein produced in the cell, and result in phenotypic consequences.