Generation of gonadless farmed cod by specific ablation of primordial germ cells

One of the greatest problems in cod aquaculture today is the premature onset of sexual maturation. This can be circumvented by sterilizing the fish using a variety of alternative methods, which differ in efficiency and undesired side-effects. In this prop osal we outline a molecular approach for specific ablation of the primordial germ cells (PGCs) in Atlantic cod. The removal of these progenitors of egg and sperm will generate gonadless fish. The PGCs maternally inherit a special cytoplasm (germ plasm) th at distinguishes these cells from somatic cells. PGCs segregate from the somatic cells following a distinct cell division pattern, and migrate through the embryo to the future site of the gonads. The recent discovery of PGC specific factors like vasa, na nos, and dead end in zebrafish has contributed substantially to the understanding of PGC development in fish. Knock-down by antisense morpholino during early cleavages resulted in sterile adults lacking gonads without any sign of abnormalties in somatic d evelopment. In teleosts, it is well known that female broodfish transfer specific immunity to egg and embryo. Together, this information raises the intriguing possibility that broodstock vaccination and immunoneutralization of key factor(s) in PGC develop ment can be used for the production of gonadless and sterile offspring.