Abstract
During zebrafish development, a gradient of stromal-derived factor 1a (Sdf1a) provides the directional cue that guides the migration of the primordial germ cells (PGCs) to the gonadal tissue. Here we describe a method to produce large numbers of infertile fish by inducing ubiquitous expression of Sdf1a in zebrafish embryos resulting in disruption of the normal PGC migration pattern. A transgenic line of zebrafish, Tg(hsp70:sdf1a-nanos3, EGFP), was generated that expresses Sdf1a under the control of the heat-shock protein 70 (hsp70) promoter and nanos3 3?UTR. To better visualize the PGCs, the Tg(hsp70:sdf1a-nanos3, EGFP) fish were crossed with another transgenic line, Tg(kop:DsRed-nanos3), that expresses DsRed driven by the PGC-specific kop promoter. Heat treatment of the transgenic embryos caused an induction of Sdf1a expression throughout the embryo resulting in the disruption of their normal migration. Optimal embryo survival and disruption of PGC migration was achieved when transgenic embryos at the 4- to 8-cell stage were incubated at 34.5°C for 18 hours. Under these conditions, disruption of PGC migration was observed in 100% of the embryos. Sixty-four adult fish were developed from three separate batches of heat-treated embryos and all were found to be infertile males. When each male was paired with a wild-type female, only unfertilized eggs were produced and histological examination revealed that each of the adult male fish possessed severely under-developed gonads that lacked gametes. The results demonstrate that inducible Sdf1a expression is an efficient and reliable strategy to produce infertile fish. This approach makes it convenient to generate large numbers of infertile adult fish while also providing the capability to maintain a fertile brood stock.
Highlights
Efficient aquaculture production is essential to meet the growing demand for aquatic food species
Results in the Development of Sterile Adult Fish Homozygous Tg(hsp70:sdf1a-nanos3, EGFP) embryos that were heat induced at 34.5uC for 18 hours beginning at the 4- to 8-cell stage were allowed to develop to adults and the fertility of the fish was examined
All of the fish were found to be males that exhibited no observable difference in primordial germ cells (PGCs)-specific DsRed expression. (B–E) Photomicrographs showing PGC migration in heat-treated Tg(hsp70:sdf1a-nanos3, EGFP)/Tg(kop:DsRed-nanos3) embryos
Summary
Efficient aquaculture production is essential to meet the growing demand for aquatic food species. As our dependence continues to shift away from wild populations towards artificially propagated aquatic species, continual optimization of aquaculture methods in an environmentally sustainable fashion will be necessary to maximize food production. Reliable strategies must be developed for the genetic containment of farmed fish to minimize environmental risk due to accidental release of the cultured species. The most effective bio-containment strategy for large-scale commercial aquaculture operations is the use of infertile farmed fish. Sterilization increases the fish growth rate by enhancing the conversion of food energy to muscle growth instead of gonad and germ cell development resulting in more efficient aquaculture production [2]. In this paper we describe an efficient and reliable strategy to generate large populations of infertile fish by disrupting the normal migration of primordial germ cells (PGCs) to the developing gonad in the fish embryo
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