Transgenic Fish Technology and Its Application in Fish Production

Abstract

Organisms into which heterologous DNA (transgene) has been artificially introduced and integrated in their genomes are called transgenics. Since the early 1980s, transgenic plants [1], nematodes [2], fruit flies [3], sea urchins [4,5], frogs [6], laboratory mice [7,8], and farm animals, such as cows, pigs, and sheep [9], have been successfully produced. In plants, transgenes are introduced into cells by infection with Agrobacterium tumefaciens or by physical means, such as ballistic bombardment. In animals, transgenes are introduced into the pronuclei of fertilized eggs by injection, and the injected embryos are incubated in vitro or implanted into the uterus of a pseudopregnant female for subsequent development. In these studies, multiple copies of transgenes are integrated at random locations in the genome of the transgenic individuals. If the transgenes are linked with functional promoters, expression of transgenes as well as display of change in phenotype is expected in some of the transgenic individuals. Furthermore, the transgenes in many transgenic individuals are also transmitted through the germline to subsequent generations. These transgenic animals play important roles in basic research as well as applied biotechnology. In basic research, transgenic animals provide excellent models for studying molecular genetics of early vertebrate development, actions of oncogenes, and the biological functions of hormones at different stages of development. In applied biotechnology, transgenic animals offer unique opportunities for producing animal models for biomedical research, improving the genetic background of broodstock for animal husbandry or aquaculture, and designing bioreactors for producing valuable proteins for pharmaceutical or industrial purposes. Since 1985, a wide of transgenic fish species have been produced [10–12] by microinjecting or electroporating homologous or heterologous transgenes into newly fertilized or unfertilized eggs. Several important steps are routinely taken to produce a desired transgenic fish. First,