The use of transient lacZ expression in fish embryos for comparative analysis of cloned regulatory elements

Transgenic fish in applied and basic research The introduction of foreign genes into fish embryos and the subsequent production of transgenic fish, have by now resulted in the accumulation of a substantial amount of data worldwide and there exists a large literature on the subject (for reviews see Maclean, Penman & Zhu, 1987; Fletcher & Davies, 1991; Hackett, 1993). The two major objectives of these studies are the production of valuable broodstock benefiting from the acquisition of desirable characteristics as well as the study of vertebrate gene regulation and the genetic basis of development. The production of transgenic fish with the desire to found genetically superior broodstock for food production has been an aim since Zhu and coworkers introduced a growth hormone gene into goldfish (1985). Attempts to increase the growth rate of farmfish species by introducing growth hormone genes have also been made by many research laboratories, some with success (Du et al. , 1992; Chen et al ., 1993; Devlin et al. , 1994). Other goals include increased freeze tolerance (Fletcher, Davies & Hew, 1992) or improved disease resistance (Leong, 1994) using transgenic technology. Fish are also becoming a popular model for the study of development and gene regulation. One approach to the study of gene regulation is the isolation and characterization of regulatory sequences and subsequent testing of their functionality in vivo or in vitro . The number of genes isolated from fish grows steadily. In a survey carried out by Maclean and Rahman (1994), the isolation of over 70 cDNA and genomic DNA sequences from a wide range of fish species by the end of 1992 is listed.