Sterility in dnd- Atlantic salmon: testicular and ovarian transcriptome

The dnd gene is essential for the development of primordial germ cells during early embryogenesis. Temporal silencing of dnd in Atlantic salmon embryos resulted in the loss of gametes and halted further reproductive development, although some males exhibited external signs of maturation. Transcriptome analyses of germ cell-ablated testes and ovaries revealed genes with important roles in reproduction, as well as genes with previously unknown functions in the gonads, for instance, a large set of genes involved in neural system development. Dnd knockdowns were produced by microinjection of “Gapmer” antisense oligonucleotides at the one-cell stage, targeting the dnd mRNA. Embryos, alevins and fry/juveniles were raised under standard hatchery conditions. Sterility/germ cell ablation was assessed by regular histology, in situ hybridization, qPCR and immunohistochemistry of the germ cell marker Vasa/ddx4. Fish were kept at a photoperiod of daily 6 h light (6L:18D) and water temperature of 5–6°C for eight weeks followed by continuous light and 10°C for six weeks according to established protocols of smoltification control. Samples of dnd knockdowns and control fish were collected at the onset of constant light (TP1) and six weeks later (TP3). At TP3, part of fish was stressed by handling and sampled after 24 hours.