Lene Kleppe

Institute of Marine Research in Norway | IMR · Bergen

Bone morphogenetic protein 15 (BMP15) is an oocyte‐specific growth factor important for successful female reproduction in mammals. While mutations in BMP15/Bmp15 cause ovulatory deficiency and/or infertility in certain mammalian species, loss of bmp15 in zebrafish, a continuous spawner and the only bmp15 knockout model in fish to date, results in c...

Although early embryonic protein production relies exclusively on maternal molecules such as messenger RNAs (mRNAs) incorporated into ovarian follicles, knowledge about any thermally induced, intergenerational effects is scarce in ectotherms. Here, we investigated how elevated temperatures (9°–12°C vs. 6°C) during oogenesis influenced the next gene...

Early puberty poses a significant challenge for male Atlantic salmon in aquaculture due to its negative impact on growth and welfare. The regulation of puberty in vertebrates involves 2 key reproductive hormones: follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and their gonadal receptors. In male mice lacking FSH receptor, testes si...

Early puberty poses a significant challenge for male Atlantic salmon in aquaculture due to its negative impact on growth and welfare. The regulation of puberty in vertebrates involves 2 key reproductive hormones: follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and their gonadal receptors. In male mice lacking FSH receptor, testes si...

Genetic introgression of farmed salmon into wild populations can damage the genetic integrity of wild stocks and is therefore considered as an environmental threat. One possible solution is to induce sterility in farmed salmon. We have searched for proteins potentially essential for germline survival in Atlantic salmon. One of these is the argonaut...

Using germ cell-free (GCF), sterile, dnd-knockout salmon for farming could solve the problems associated with precocious maturation and genetic introgression of farmed breeds into wild populations. However, prior to using GCF fish in the salmon farming industry, it is crucial to understand if, or how, the GCF phenotype differs from wild type (WT) c...

Precocious male maturation causes reduced welfare and increased production costs in Atlantic salmon (Salmo salar) aquaculture. The pituitary produces and releases follicle-stimulating hormone (Fsh), the gonadotropin triggering puberty in male salmonids. However, little is known about how Fsh production is regulated in Atlantic salmon. We examined,...

Atlantic Halibut (Hippoglossus hippoglossus) has a X/Y genetic sex determination system, but the sex determining factor is not known. We produced a high-quality genome assembly from a male and identified parts of chromosome 13 as the Y chromosome due to sequence divergence between sexes and segregation of sex genotypes in pedigrees. Linkage analysi...

Entering meiosis strictly depends on stimulated by retinoic acid 8 (Stra8) gene function in mammals. This gene is missing in a number of fish species, including medaka and zebrafish, but is present in the majority of fishes, including Atlantic salmon. Here, we have examined the effects of removing stra8 on male fertility in Atlantic salmon. As in m...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Atlantic Halibut (Hippoglossus hippoglossus) has a X/Y genetic sex determination system, but the sex determining factor is not known. We produced a high-quality genome assembly and identified parts of chromosome 13 as the Y chromosome due to sequence divergence between sexes and segregation of sex genotypes in pedigrees. Linkage analysis revealed t...

Genetic introgression of escaped farmed Atlantic salmon (Salmo salar) into wild populations is a major environmental concern for the salmon aquaculture industry. Using sterile fish in commercial aquaculture operations is, therefore, a sustainable strategy for bio-containment. So far, the only commercially used methodology for producing sterile fish...

Background: Sustainability challenges are currently hampering an increase in salmon production. Using sterile salmon can solve problems with precocious puberty and genetic introgression from farmed escapees to wild populations. Recently sterile salmon was produced by knocking out the germ cell-specific dead end (dnd). Several approaches may be app...

Precise gene editing such as CRISPR/Cas9-mediated homology directed repair (HDR) can increase our understanding of gene function and improve traits of importance for aquaculture. This fine-tuned technology has not been developed for farmed fish including Atlantic salmon. We performed knock-in (KI) of a FLAG element in the slc45a2 gene in salmon usi...

Background Sustainability challenges are currently hampering an increase in salmon production. Using sterile salmon can solve problems with precocious puberty and genetic introgression from farmed escapees to wild populations. Recently sterile salmon was produced by knocking out the germ cell-specific dead end (dnd). Several approaches may be appli...

Background Sustainability challenges are currently hampering an increase in salmon production. Using sterile salmon can solve problems with precocious puberty and genetic introgression from farmed escapees to wild populations. Recently sterile salmon was produced by knocking out the germ cell-specific dead end (dnd). Several approaches may be appli...

The temperature is one of the key parameters of climate change influencing teleost physiology and population dynamics. In addition, the thermal windows for spawners and early life stages (eggs and larvae) appear to be the narrowest during the life of the fish. The maternal contribution to fish embryogenesis is clearly established as this latter dep...

Vgll3 is linked to age at maturity in Atlantic salmon (Salmo salar). However, the molecular mechanisms involving Vgll3 in controlling timing of puberty as well as relevant tissue and cell types are currently unknown. Vgll3 and the associated Hippo pathway has been linked to reduced proliferation activity in different tissues. Analysis of gene expre...

Background Our understanding of the molecular mechanisms implementing pubertal maturation of the testis in vertebrates is incomplete. This topic is relevant in Atlantic salmon aquaculture, since precocious male puberty negatively impacts animal welfare and growth. We hypothesize that certain miRNAs modulate mRNAs relevant for the initiation of pube...

In all vertebrates studied so far, germ cells are not required for pubertal maturation of the gonadal steroidogenic system, subsequent development of secondary sex characteristics and reproductive behavior. To explore if the absence of germ cells affects puberty or growth in Atlantic salmon, germ cell-free (GCF), dnd knockout and wild type (WT) pos...

The present study was designed to investigate potential effects of arachidonic acid (ARA) on the reproductive physiology of female Atlantic cod (Gadus morhua L.). Two-year old Atlantic cod of both sexes were equally distributed into eight sea cages after completion of their first spawning in May 2005. Four experimental groups were established and f...

Atlantic salmon is a valuable commercial aquaculture species that would benefit economically and environmentally by controlling precocious puberty and preventing escapees from reproducing with wild populations. One solution to both these challenges is the production of sterile individuals by inhibiting the formation of germ cells, but achieving thi...

In Atlantic salmon, a species of great relevance for aquaculture in Northern Europe, precocious puberty in males increases susceptibility to disease, affects flesh quality, reduces growth and cause hypo-osmoregulatory problems (Taranger et al. 2010). It is therefore of high importance to understand the underlying causative molecular processes invol...

Introgression of farmed salmon escapees into wild stocks is a major threat to the genetic integrity of wild populations. Using germ cell-free fish in aquaculture may mitigate this problem. Our study investigated whether it is possible to produce germ cell-free salmon in F0 by using CRISPR-Cas9 to knock out dnd, a factor required for germ cell survi...

Fish in use in aquaculture display large variation in gamete biology. To reach better understanding around this issue, this study aims at identifying if species specific "egg life history traits" can be hidden in the unfertilized egg. This was done by investigating egg transcriptome differences between Atlantic salmon and Atlantic cod. Salmon and c...

Understanding the biological function behind key proteins is of great concern in Atlantic salmon, both due to a high commercial importance and an interesting life history. Until recently, functional studies in salmonids appeared to be difficult. However, the recent discovery of targeted mutagenesis using the CRISPR/Cas9 (clustered regularly intersp...

The molecular mechanisms underlying oogenesis and maternally controlled embryogenesis in fish are not fully understood, especially in marine species. Our aim was to study the egg and embryo transcriptome during oogenesis and early embryogenesis in Atlantic cod. Follicles from oogenesis stages (pre-, early-, and late-vitellogenic), ovulated eggs, an...

Introduction Previous studies have revealed a differential expression of small RNA repertoires between immature and mature testis, however no such global small RNA expression studies have been performed in salmonides. Since both precocious maturation and fertility are current problems in salmon aquaculture, increased knowledge about molecular regul...

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Zygotic transcription in fish embryos initiates around the time of gastrulation, and all prior development is initiated and controlled by maternally derived messenger RNAs. Atlantic cod egg and embryo viability is variable, and it is hypothesized that the early development depends upon the feature of these maternal RNAs. Both the length and the pre...

Gene expression of reference genes in oocyte, 1-2 cell, blastula and gastrula stage in cod. mRNA levels are shown as cycle threshold (Ct)-values when 250 ng RNA was used for cDNA synthesis. All data are shown as mean with SEM. N = 2.

Results from repeated 3’UTR structure analyses, with less strict criteria for classification and excluding all ribosomal genes. Results from repeated analyses on 3’UTR structure, with less strict classification of gene groups and excluding all ribosomal genes. In addition to genes with above 95% of transcripts present in oocyte until blastula stage...

Distribution of nuclear genes with and without transcript number threshold. The bar to the left represents the proportion of nuclear genes that were expressed exclusively in maternal stages, gastrula or in all four stages, when analyzing the dataset with a transcript number threshold (n > 8). The bar to the right represents the dataset when no thre...

Gene Ontology annotation based on UniRef90 BLAST hits. This file contains Gene Ontology annotation based on UniRef90 BLAST hits. 1) UniRef hit, 2) Ensembl gene, 3) Ensembl annotation, 4) UniRef90 hit, 5) UniRef90 hit e-value, 6) UniRef90 hit score, 7) Total UniRef90 hits in the whole predicted gene set, 8) GO UniRef, 9) GO gene name, 10) GO number,...

Gene expression levels of candidate genes to reveal timing of midblastula transition in cod. mRNA levels of 3 candidate genes were measured in oocyte, 1-2 cell, blastula and gastrula stage. mRNA levels are relative to hba. Bars with different letters represent significant different mRNA levels for each gene. All data are shown as mean with SEM. N =...

Functional profile of transcripts that showed a difference in abundance between maternal and zygotic stages. Three levels of function (parent ontologies) are shown: cellular component, molecular function and biological process. The number on top of each bar represents the total number of transcripts in that stage, which could be coupled to the pare...

Contig annotations. This file shows the mapping of EST-contigs to the Atlantic cod genome. Contig annotations for the 257 genes analysed in this study are shown.

Contigs based on clustered sequences. This file contains clustered sequences from all libraries, with given contig name. The contig name can be linked to annotation and accession number in [Additional file 7].

Broodstock management and nutrition is vital for successful aquaculture, in order to ensure a stable production of viable offspring. Good practises in this area will promote general fish health, production efficiency, and the quality of the final product. While most studies on fish broodstock nutrition have focused on realised fecundity and viabili...