mtR_find: A Parallel Processing Tool to Identify and Annotate RNAs Derived from the Mitochondrial Genome.

RNAs originating from mitochondrial genomes are abundant in transcriptomic datasets produced by high-throughput sequencing technologies, primarily in short-read outputs. Specific features of mitochondrial small RNAs (mt-sRNAs), such as non-templated additions, presence of length variants, sequence variants, and other modifications, necessitate the need for the development of an appropriate tool for their effective identification and annotation. We have developed mtR_find, a tool to detect and annotate mitochondrial RNAs, including mt-sRNAs and mitochondria-derived long non-coding RNAs (mt-lncRNA). mtR_find uses a novel method to compute the count of RNA sequences from adapter-trimmed reads. When analyzing the published datasets with mtR_find, we identified mt-sRNAs significantly associated with the health conditions, such as hepatocellular carcinoma and obesity, and we discovered novel mt-sRNAs. Furthermore, we identified mt-lncRNAs in early development in mice. These examples show the immediate impact of miR_find in extracting a novel biological information from the existing sequencing datasets. For benchmarking, the tool has been tested on a simulated dataset and the results were concordant. For accurate annotation of mitochondria-derived RNA, particularly mt-sRNA, we developed an appropriate nomenclature. mtR_find encompasses the mt-ncRNA transcriptomes in unpreceded resolution and simplicity, allowing re-analysis of the existing transcriptomic databases and the use of mt-ncRNAs as diagnostic or prognostic markers in the field of medicine.

Structural Organization of S516 Group I Introns in Myxomycetes.

Group I introns are mobile genetic elements encoding self-splicing ribozymes. Group I introns in nuclear genes are restricted to ribosomal DNA of eukaryotic microorganisms. For example, the myxomycetes, which represent a distinct protist phylum with a unique life strategy, are rich in nucleolar group I introns. We analyzed and compared 75 group I introns at position 516 in the small subunit ribosomal DNA from diverse and distantly related myxomycete taxa. A consensus secondary structure revealed a conserved group IC1 ribozyme core, but with a surprising RNA sequence complexity in the peripheral regions. Five S516 group I introns possess a twintron organization, where a His-Cys homing endonuclease gene insertion was interrupted by a small spliceosomal intron. Eleven S516 introns contained direct repeat arrays with varying lengths of the repeated motif, a varying copy number, and different structural organizations. Phylogenetic analyses of S516 introns and the corresponding host genes revealed a complex inheritance pattern, with both vertical and horizontal transfers. Finally, we reconstructed the evolutionary history of S516 nucleolar group I introns from insertion of mobile-type introns at unoccupied cognate sites, through homing endonuclease gene degradation and loss, and finally to the complete loss of introns. We conclude that myxomycete S516 introns represent a family of genetic elements with surprisingly dynamic structures despite a common function in RNA self-splicing.

A Phylogenetic Approach to Structural Variation in Organization of Nuclear Group I Introns and Their Ribozymes.

Nuclear group I introns are restricted to the ribosomal DNA locus where they interrupt genes for small subunit and large subunit ribosomal RNAs at conserved sites in some eukaryotic microorganisms. Here, the myxomycete protists are a frequent source of nuclear group I introns due to their unique life strategy and a billion years of separate evolution. The ribosomal DNA of the myxomycete Mucilago crustacea was investigated and found to contain seven group I introns, including a direct repeat-containing intron at insertion site S1389 in the small subunit ribosomal RNA gene. We collected, analyzed, and compared 72 S1389 group IC1 introns representing diverse myxomycete taxa. The consensus secondary structure revealed a conserved ribozyme core, but with surprising sequence variations in the guanosine binding site in segment P7. Some S1389 introns harbored large extension sequences in the peripheral region of segment P9 containing direct repeat arrays. These repeats contained up to 52 copies of a putative internal guide sequence motif. Other S1389 introns harbored homing endonuclease genes in segment P1 encoding His-Cys proteins. Homing endonuclease genes were further interrupted by small spliceosomal introns that have to be removed in order to generate the open reading frames. Phylogenetic analyses of S1389 intron and host gene indicated both vertical and horizontal intron transfer during evolution, and revealed sporadic appearances of direct repeats, homing endonuclease genes, and guanosine binding site variants among the myxomycete taxa.

Altered non-coding RNA expression profile in F1 progeny 1 year after parental irradiation is linked to adverse effects in zebrafish.

Gamma radiation produces DNA instability and impaired phenotype. Previously, we observed negative effects on phenotype, DNA methylation, and gene expression profiles, in offspring of zebrafish exposed to gamma radiation during gametogenesis. We hypothesize that previously observed effects are accompanied with changes in the expression profile of non-coding RNAs, inherited by next generations. Non-coding RNA expression profile was analysed in F1 offspring (5.5 h post-fertilization) by high-throughput sequencing 1 year after parental irradiation (8.7 mGy/h, 5.2 Gy total dose). Using our previous F1-γ genome-wide gene expression data (GSE98539), hundreds of mRNAs were predicted as targets of differentially expressed (DE) miRNAs, involved in pathways such as insulin receptor, NFkB and PTEN signalling, linking to apoptosis and cancer. snRNAs belonging to the five major spliceosomal snRNAs were down-regulated in the F1-γ group, Indicating transcriptional and post-transcriptional alterations. In addition, DEpiRNA clusters were associated to 9 transposable elements (TEs) (LTR, LINE, and TIR) (p = 0.0024), probable as a response to the activation of these TEs. Moreover, the expression of the lincRNAs malat-1, and several others was altered in the offspring F1, in concordance with previously observed phenotypical alterations. In conclusion, our results demonstrate diverse gamma radiation-induced alterations in the ncRNA profiles of F1 offspring observable 1 year after parental irradiation.

Some recent data on sperm morphology and motility kinetics in Atlantic cod (Gadus morhua L.).

Studying biology of sperm provides valuable information to optimize artificial reproduction and is crucial for sustainable aquaculture. Here, we investigated morphology of spermatozoon in Atlantic cod (Gadus morhua) using transmission and scanning electron microscopy. Furthermore, spermatozoa motility kinetics at different osmolalities were studied using computer-assisted sperm analysis software. The spermatozoon lacked an acrosome and consisted of a head, midpiece, and flagellum. The head of spermatozoa was round, oval, and rather elongated in shape, showing high variations in dimensions. There were up to 6 mitochondria that encircled the proximal part of the flagellum. The proximal and distal centrioles were located within the nuclear notch and arranged orthogonal to each other. The axoneme had a typical 9 + 2 microtubule structure. The flagellar length of spermatozoon was 66.94 ± 0.46 µm. Spermatozoa were immotile in the seminal plasma. Dilution of sperm with natural seawater (1100 mOsmol/kg) resulted in initiation of motility for 91.0 ± 3.4% of spermatozoa with average velocity of 86.2 ± 2.3 µm/s and beating frequency of 52 Hz. The duration of spermatozoa motility was > 6 min; however, the percentage of motile spermatozoa decreased at 60 s post-activation. When osmolality of natural seawater was modified using distilled water or NaCl, spermatozoa motility was not initiated at ≤ 400 and ≥ 2500 mOsmol/kg, and the highest percentage of motility was observed at 730-1580 mOsmol/kg. In a sucrose solution, spermatozoa motility was initiated and suppressed at 600 and 1500 mOsmol/kg, respectively, and highest percentage of motility was observed at 800-1100 mOsmol/kg. Spermatozoon morphology comparisons within Gadiformes showed differences in dimensions of head and mitochondria, flagellar length, and number of mitochondria. The present study provides valuable data that can be used for phylogenetic implications based on spermatozoon morphology and for development of artificial fertilization and sperm cryopreservation protocols based on sperm motility.

The shift from early to late types of ribosomes in zebrafish development involves changes at a subset of rRNA 2'-O-Me sites.

During zebrafish development, an early type of rRNA is gradually replaced by a late type that is substantially different in sequence. We applied RiboMeth-seq to rRNA from developmental stages for profiling of 2'-O-Me, to learn if changes in methylation pattern were a component of the shift. We compiled a catalog of 2'-O-Me sites and cognate box C/D guide RNAs comprising 98 high-confidence sites, including 10 sites that were not known from other vertebrates, one of which was specific to late-type rRNA. We identified a subset of sites that changed in methylation status during development and found that some of these could be explained by availability of their cognate SNORDs. Sites that changed during development were enriched in the novel sites revealed in zebrafish. We propose that the early type of rRNA is a specialized form and that its structure and ribose methylation pattern may be an adaptation to features of development, including translation of specific maternal mRNAs.

High-Throughput Identification of Adapters in Single-Read Sequencing Data.

Sequencing datasets available in public repositories are already high in number, and their growth is exponential. Raw sequencing data files constitute a substantial portion of these data, and they need to be pre-processed for any downstream analyses. The removal of adapter sequences is the first essential step. Tools available for the automated detection of adapters in single-read sequencing protocol datasets have certain limitations. To explore these datasets, one needs to retrieve the information on adapter sequences from the methods sections of appropriate research articles. This can be time-consuming in metadata analyses. Moreover, not all research articles provide the information on adapter sequences. We have developed adapt_find, a tool that automates the process of adapter sequences identification in raw single-read sequencing datasets. We have verified adapt_find through testing a number of publicly available datasets. adapt_find secures a robust, reliable and high-throughput process across different sequencing technologies and various adapter designs. It does not need prior knowledge of the adapter sequences. We also produced associated tools: random_mer, for the detection of random N bases either on one or both termini of the reads, and fastqc_parser, for consolidating the results from FASTQC outputs. Together, this is a valuable tool set for metadata analyses on multiple sequencing datasets.

Heterogenic Origin of Micro RNAs in Atlantic Salmon (Salmo salar) Seminal Plasma.

The origin and contribution of seminal plasma RNAs into the whole semen RNA repertoire are poorly known, frequently being overlooked or neglected. In this study, we used high-throughput sequencing and RT-qPCR to profile microRNA (miRNA) constituents in the whole semen, as well as in fractionated spermatozoa and seminal plasma of Atlantic salmon (Salmo salar). We found 85 differentially accumulated miRNAs between spermatozoa and the seminal plasma. We identified a number of seminal plasma-enriched and spermatozoa-enriched miRNAs. We localized the expression of some miRNAs in juvenile and mature testes. Two abundant miRNAs, miR-92a-3p and miR-202-5p, localized to both spermatogonia and somatic supporting cells in immature testis, and they were also highly abundant in somatic cells in mature testis. miR-15c-5p, miR-30d-5p, miR-93a-5p, and miR-730-5p were detected only in mature testis. miRs 92a-3p, 202-5p, 15c-5p, and 30d-5p were also detected in a juvenile ovary. The RT-qPCR experiment demonstrated lack of correlation in miRNA transcript levels in seminal plasma versus blood plasma. Our results indicate that salmon semen is rich in miRNAs, which are present in both spermatozoa and seminal plasma. Testicular-supporting somatic cells are likely the source of seminal plasma enrichment, whereas blood plasma is unlikely to contribute to the seminal plasma miRNA repertoire.

Proteomics Analysis of Early Developmental Stages of Zebrafish Embryos.

Zebrafish is a well-recognized organism for investigating vertebrate development and human diseases. However, the data on zebrafish proteome are scarce, particularly during embryogenesis. This is mostly due to the overwhelming abundance of egg yolk proteins, which tend to mask the detectable presence of less abundant proteins. We developed an efficient procedure to reduce the amount of yolk in zebrafish early embryos to improve the Liquid chromatography-tandem mass spectrometry (LC-MS)-based shotgun proteomics analysis. We demonstrated that the deyolking procedure resulted in a greater number of proteins being identified. This protocol resulted in approximately 2-fold increase in the number of proteins identified in deyolked samples at cleavage stages, and the number of identified proteins increased greatly by 3-4 times compared to non-deyolked samples in both oblong and bud stages. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed a high number of functional proteins differentially accumulated in the deyolked versus non-deyolked samples. The most prominent enrichments after the deyolking procedure included processes, functions, and components related to cellular organization, cell cycle, control of replication and translation, and mitochondrial functions. This deyolking procedure improves both qualitative and quantitative proteome analyses and provides an innovative tool in molecular embryogenesis of polylecithal animals, such as fish, amphibians, reptiles, or birds.

Postovulatory maternal transcriptome in Atlantic salmon and its relation to developmental potential of embryos.

BACKGROUND: Early development of an oviparous organism is based on maternally stocked structural, nutritional and regulatory components. These components influence the future developmental potential of an embryo, which is referred to as egg quality. Until zygotic genome activation, translational activity in a fish early embryo is limited to parentally inherited transcripts only. In this study, we asked whether egg transcriptome is associated with egg quality in Atlantic salmon (Salmo salar), which is capable of storing ovulated eggs in its abdominal cavity for a long time before spawning. RESULTS: We analyzed messenger RNA (mRNA) and micro RNA (miRNA) transcriptomes throughout the post-ovulatory egg retention period in batches of eggs from two quality groups, good and poor, classified based on the future developmental performance. We identified 28,551 protein-coding genes and 125 microRNA families, with 200 mRNAs and 5 miRNAs showing differential abundance between egg quality groups and/or among postovulatory ages. Transcriptome dynamics during the egg retention period was different in the two egg quality groups. We identified only a single gene, hepcidin-1, as a potential marker for Atlantic salmon egg quality evaluation. CONCLUSION: The overlapping effect of post-ovulatory age on intrinsic egg developmental competence makes the quantification of egg quality difficult when based on transcripts abundance only.

Low incubation temperature during early development negatively affects survival and related innate immune processes in zebrafish larvae exposed to lipopolysaccharide.

In many fish species, the immune system is significantly constrained by water temperature. In spite of its critical importance in protecting the host against pathogens, little is known about the influence of embryonic incubation temperature on the innate immunity of fish larvae. Zebrafish (Danio rerio) embryos were incubated at 24, 28 or 32 °C until first feeding. Larvae originating from each of these three temperature regimes were further distributed into three challenge temperatures and exposed to lipopolysaccharide (LPS) in a full factorial design (3 incubation × 3 challenge temperatures). At 24 h post LPS challenge, mortality of larvae incubated at 24 °C was 1.2 to 2.6-fold higher than those kept at 28 or 32 °C, regardless of the challenge temperature. LPS challenge at 24 °C stimulated similar immune-related processes but at different levels in larvae incubated at 24 or 32 °C, concomitantly with the down-regulation of some chemokine and lysozyme transcripts in the former group. Larvae incubated at 24 °C and LPS-challenged at 32 °C exhibited a limited immune response with up-regulation of hypoxia and oxidative stress processes. Annexin A2a, S100 calcium binding protein A10b and lymphocyte antigen-6, epidermis were identified as promising candidates for LPS recognition and signal transduction.

Dynamics of miRNA transcriptome during gonadal development of zebrafish.

Studies in non-teleost vertebrates have found microRNAs (miRNAs) to be essential for proper gonadal development. However, comparatively little is known about their role during gonadal development in teleost fishes. So far in zebrafish, a model teleost, transcript profiling throughout gonadal development has not been established because of a tiny size of an organ in juvenile stages and its poor distinguishability from surrounding tissues. We performed small RNA sequencing on isolated gonads of See-Thru-Gonad line, from the undifferentiated state at 3 weeks post fertilization (wpf) to fully mature adults at 24 wpf. We identified 520 gonadal mature miRNAs; 111 of them had significant changes in abundance over time, while 50 miRNAs were either testis- or ovary-enriched significantly in at least one developmental stage. We characterized patterns of miRNA abundance over time including isomiR variants. We identified putative germline versus gonadal somatic miRNAs through differential small RNA sequencing of isolated gametes versus the whole gonads. This report is the most comprehensive analysis of the miRNA repertoire in zebrafish gonads during the sexual development to date and provides an important database from which functional studies can be performed.

See-Thru-Gonad zebrafish line: developmental and functional validation.

Zebrafish are an important model species in developmental biology. However, their potential in reproductive biology research has yet to be realized. In this study, we established See-Thru-Gonad zebrafish, a transparent line with fluorescently labeled germ cells visible throughout the life cycle, validated its gonadal development features, and demonstrated its applicability by performing a targeted gene knockdown experiment using vivo-morpholinos (VMOs). To establish the line, we crossed the zf45Tg and mitfa(w2/w2); mpv17(b18/b18) zebrafish lines. We documented the in vivo visibility of the germline-specific fluorescent signal throughout development, from gametes through embryonic and juvenile stages up to sexual maturity, and validated gonadal development with histology. We performed targeted gene knockdown of the microRNA (miRNA) miR-92a-3p through injection of VMOs directly to maturing ovaries. After the treatment, zebrafish were bred naturally. Embryos from miR-92a-3p knockdown ovaries had a significant reduction in relative miR-92a-3p expression and a higher percentage of developmental arrest at the 1-cell stage as compared with 5-base mismatch-treated controls. The experiment demonstrates that See-Thru-Gonad line can be successfully used for vertical transmission of the effects of targeted gene knockdown in ovaries into their offspring.

First feed affects the expressions of microRNA and their targets in Atlantic cod.

To our knowledge, there is no report on microRNA (miRNA) expression and their target analysis in relation to the type of the first feed and its effect on the further growth of fish. Atlantic cod (Gadus morhua) larvae have better growth and development performance when fed natural zooplankton as a start-feed, as compared with those fed typical aquaculture start-feeds. In our experiment, two groups of Atlantic cod larvae were fed reference feed (zooplankton, mostly copepods, filtered from a seawater pond) v. aquaculture feeds: enriched rotifers (Brachionus sp.) and later brine shrimp (Artemia salina). We examined the miRNA expressions of six defined developmental stages as determined and standardised by body length from first feeding for both diet groups. We found eight miRNA (miR-9, miR-19a, miR-130b, miR-146, miR-181a, miR-192, miR-206 and miR-11240) differentially expressed between the two feeding groups in at least one developmental stage. We verified the next-generation sequencing data using real-time RT-PCR. We found 397 putative targets (mRNA) to the differentially expressed miRNA; eighteen of these mRNA showed differential expression in at least one stage. The patterns of differentially expressed miRNA and their putative target mRNA were mostly inverse, but sometimes also concurrent. The predicted miRNA targets were involved in different pathways, including metabolic, phototransduction and signalling pathways. The results of this study provide new nutrigenomic information on the potential role of miRNA in mediating nutritional effects on growth during the start-feeding period in fish larvae.

Some quantitative indicators of postovulatory aging and its effect on larval and juvenile development of Atlantic salmon (Salmo salar).

Modern out-of-season egg production in Atlantic salmon (Salmo salar) increases the risk of postovulatory aging (POA) of oocytes. Postovulatory aging is known to influence oocyte quality in salmonids, but reliable tests for POA are lacking in Atlantic salmon egg production. To address this problem, we have collected oocytes from the same 20 Atlantic salmon females sequentially in approximately 1-week intervals, from the start of ovulation until 28 days postovulation (dpo), to determine the effect of natural retention of matured oocytes in body coelomic cavity on further performance of embryos and juveniles produced from those oocytes. Also, we investigated oocyte water hardening and several coelomic fluid parameters as potential quantitative indicators of POA. Oocyte quality decreased significantly from 22 dpo onward, as inferred from decrease in fertilization success and survival of embryos, alevins, and juveniles and increase in alevin and juvenile deformity rates. The occurrence of head deformities was significantly related to postovulatory age of oocytes. Coelomic fluid pH decreased significantly at 28 dpo and correlated positively with fertilization rates (r = 0.45), normal eyed embryo rates (r = 0.67), and alevin relative survival rates (r = 0.63) and negatively correlated with total alevin deformity rates (r = -0.59). Oocyte weight gain at 60 minutes decreased significantly at 28 dpo and correlated negatively with total alevin deformities and the occurrence of cranial nodules (r = -0.99). Generally, quality of ovulated oocytes remained stable for the first 2 weeks after ovulation. Later on, POA negatively influenced Atlantic salmon embryo, alevin, and juvenile performance. For the first time, we show a long-term effect of POA on salmonid juvenile performance. Standardized pH measurements of coelomic fluid could potentially improve embryo and juvenile production by identifying low-quality oocytes at an early stage during the production.

Temperature during early development has long-term effects on microRNA expression in Atlantic cod.

BACKGROUND: Environmental temperature has serious implications in life cycle of aquatic ectotherms. Understanding the molecular mechanisms of temperature acclimation and adaptation of marine organisms is of the uttermost importance for ecology, fisheries, and aquaculture, as it allows modeling the effects of global warming on population dynamics. Regulatory molecules are major modulators of acclimation and adaptation; among them, microRNAs (miRNAs) are versatile and substantial contributors to regulatory networks of development and adaptive plasticity. However, their role in thermal plasticity is poorly known. We have asked whether the temperature and its shift during the early ontogeny (embryonic and larval development) affect the miRNA repertoire of Atlantic cod (Gadus morhua), and if thermal experience has long-term consequences in the miRNA profile. RESULTS: We characterized miRNA during different developmental stages and in juvenile tissues using next generation sequencing. We identified 389 putative miRNA precursor loci, 120 novel precursor miRNAs, and 281 mature miRNAs. Some miRNAs showed stage- or tissue-enriched expression and miRNAs, such as the miR-17 ~ 92 cluster, myomiRs (miR-206), neuromiRs (miR-9, miR-124), miR-130b, and miR-430 showed differential expression in different temperature regimes. Long-term effect of embryonic incubation temperature was revealed on expression of some miRNAs in juvenile pituitary (miR-449), gonad (miR-27c, miR-30c, and miR-200a), and liver (let-7 h, miR-7a, miR-22, miR-34c, miR-132a, miR-192, miR-221, miR-451, miR-2188, and miR-7550), but not in brain. Some of differentially expressed miRNAs in the liver were confirmed using LNA-based rt-qPCR. The effect of temperature on methylation status of selected miRNA promoter regions was mostly inconclusive. CONCLUSIONS: Temperature elevation by several degrees during embryonic and larval developmental stages significantly alters the miRNA profile, both short-term and long-term. Our results suggest that a further rise in seas temperature might affect life history of Atlantic cod.

Quantitative characteristics of Atlantic halibut (Hippoglossus hippoglossus L.) egg quality throughout the reproductive season.

Assessment of egg quality is an important aspect in finfish hatchery management, but guidelines for such assessment are scarce, especially for marine fish production. In the present work, potential indicators of egg and larval quality were measured in 39 batches of eggs of Atlantic halibut (Hippoglossus hippoglossus L.) throughout the reproductive season. The paternal influence on offspring was minimized by using the same cryopreserved semen for all fertilizations; consequently, maternal effects were emphasized. The progression of the spawning season and ovarian fluid parameters, including pH, electrical conductivity (EC), osmolality, and the amount of fluid were registered. The behavior of the broodfish at egg collection was registered and the eggs were analyzed for cortisol content. Fertilization and hatching rates as well as larvae survival were calculated, and larval standard length and myotome height were measured. Furthermore, the occurrence of major types of larval deformities was registered. The myotome height was significantly (P < 0.05) affected by the spawning season progress. Cortisol content in the eggs was decreasing with the progressing spawning season and correlated positively with the occurrence of yolk-sac edema. The ovarian fluid pH and EC were significantly related to fertilization and hatching rates. High fertilization and hatching success was associated with pH greater than 7.9 and EC less than 2.5 mS/cm. Low fertilization rates (< 50%) resulted in further low hatchability from such egg batches. Ovarian fluid EC was significantly and positively related to increased occurrence of yolk-sac edema. High quantity of ovarian fluid in egg batches was associated with reduced egg quality in terms of fertilization and hatching rates and occurrence of yolk-sac edema. A cumulative effect of ovarian fluid pH, EC, osmolality, and quantity explained up to 62% of the total variation in fertilization rates. The findings from the present study indicate that parameters measurable at the initial phase of production, in particular ovarian fluid pH and EC, might have a potential for future use as egg quality indicators in hatchery management.

Induced autoimmunity against gonadal proteins affects gonadal development in juvenile zebrafish.

A method to mitigate or possibly eliminate reproduction in farmed fish is highly demanded. The existing approaches have certain applicative limitations. So far, no immunization strategies affecting gonadal development in juvenile animals have been developed. We hypothesized that autoimmune mechanisms, occurring spontaneously in a number of diseases, could be induced by targeted immunization. We have asked whether the immunization against specific targets in a juvenile zebrafish gonad will produce an autoimmune response, and, consequently, disturbance in gonadal development. Gonadal soma-derived factor (Gsdf), growth differentiation factor (Gdf9), and lymphocyte antigen 75 (Cd205/Ly75), all essential for early gonad development, were targeted with 5 immunization tests. Zebrafish (n = 329) were injected at 6 weeks post fertilization, a booster injection was applied 15 days later, and fish were sampled at 30 days. We localized transcripts encoding targeted proteins by in situ hybridization, quantified expression of immune-, apoptosis-, and gonad-related genes with quantitative real-time PCR, and performed gonadal histology and whole-mount immunohistochemistry for Bcl2-interacting-killer (Bik) pro-apoptotic protein. The treatments resulted in an autoimmune reaction, gonad developmental retardation, intensive apoptosis, cell atresia, and disturbed transcript production. Testes were remarkably underdeveloped after anti-Gsdf treatments. Anti-Gdf9 treatments promoted apoptosis in testes and abnormal development of ovaries. Anti-Cd205 treatment stimulated a strong immune response in both sexes, resulting in oocyte atresia and strong apoptosis in supporting somatic cells. The effect of immunization was FSH-independent. Furthermore, immunization against germ cell proteins disturbed somatic supporting cell development. This is the first report to demonstrate that targeted autoimmunity can disturb gonadal development in a juvenile fish. It shows a straightforward potential to develop auto-immunization-based technologies to mitigate fish reproduction before they reach maturation. However, the highly variable results between treatments and individuals suggest significant optimization should be performed to achieve the full potential of this technology.

Profiling of the embryonic Atlantic halibut (Hippoglossus hippoglossus L.) transcriptome reveals maternal transcripts as potential markers of embryo quality.

BACKGROUND: Commercial Atlantic halibut (Hippoglossus hippoglossus) farming is restricted by variable oocyte quality, slow growth, and early maturation of male fish. Maternally transferred components regulate early developmental processes; therefore, they have an effect on the future viability of the embryo. Using a newly developed Agilent 10 k custom-made oligonucleotide array, we profiled components of the transcriptome involved in immune defence as well as germline and muscle development during early developmental stages: 8-cell embryos (8CS), germ ring stage (GR), 10-somite stage (10SS), and hatched embryos (HT). In addition, we identified differentially expressed transcripts in low (≤9 ± 3% hatching) and high (≥86 ± 3°% hatching) quality eggs at 8CS to identify potential maternal markers for embryo quality. RESULTS: Out of 2066 differentially expressed transcripts, 160 were identified as maternal transcripts being specifically expressed at 8CS only. Twenty transcripts were differentially expressed in 8-cell embryos between low and high quality egg groups. Several immune-related transcripts were identified as promising molecular markers of hatching success including interferon regulatory factor 7 and mhc class 2A chain. Differential expression was positively validated with quantitative real-time PCR. CONCLUSIONS: We have demonstrated maternal transfer of innate and adaptive immune system transcripts into Atlantic halibut embryos and their relation with future embryo developmental potential. We identified several transcripts as potential molecular markers of embryo quality. The developed microarray represents a useful resource for improving the commercial production of Atlantic halibut.