Substantial Downregulation of Myogenic Transcripts in Skeletal Muscle of Atlantic Cod during the Spawning Period.
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ABSTRACT:
SUBMITTER: Nagasawa K
PROVIDER: S-EPMC4742245 | biostudies-literature | 2016
REPOSITORIES: biostudies-literature
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Project description:The classical notion of a centralized clock that governs circadian rhythmicity has been challenged with the discovery of peripheral oscillators that enable organisms to cope with daily changes in their environment. The present study aimed to identify the molecular clock components in Atlantic cod (Gadus morhua) and to investigate their daily gene expression in fast skeletal muscle. Atlantic cod clock genes were closely related to their orthologs in teleosts and tetrapods. Synteny was conserved to varying degrees in the majority of the 18 clock genes examined. In particular, aryl hydrocarbon receptor nuclear translocator-like 2 (arntl2), RAR-related orphan receptor A (rora) and timeless (tim) displayed high degrees of conservation. Expression profiling during the early ontogenesis revealed that some transcripts were maternally transferred, namely arntl2, cryptochrome 1b and 2 (cry1b and cry2), and period 2a and 2b (per2a and per2b). Most clock genes were ubiquitously expressed in various tissues, suggesting the possible existence of multiple peripheral clock systems in Atlantic cod. In particular, they were all detected in fast skeletal muscle, with the exception of neuronal PAS (Per-Arnt-Single-minded) domain-containing protein (npas1) and rora. Rhythmicity analysis revealed 8 clock genes with daily rhythmic expression, namely arntl2, circadian locomotor output cycles kaput (clock), npas2, cry2, cry3 per2a, nuclear receptor subfamily 1, group D, member 1 (nr1d1), and nr1d2a. Transcript levels of the myogenic genes myogenic factor 5 (myf5) and muscleblind-like 1 (mbnl1) strongly correlated with clock gene expression. This is the first study to unravel the molecular components of peripheral clocks in Atlantic cod. Taken together, our data suggest that the putative clock system in fast skeletal muscle of Atlantic cod has regulatory implications on muscle physiology, particularly in the expression of genes related to myogenesis.
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Project description:Specific changes identified in the otolith macrostructure of Northeast Arctic cod as "spawning zones" are presumed to represent spawning events, but recent experimental studies have challenged this relationship. Because these zones are not routinely recorded outside of Norway, otoliths from multiple Atlantic cod populations with different life history and environmental traits were first examined to see if spawning zones could be identified as a general characteristic of cod. Then, a large archival collection of cod otoliths was used to investigate temporal changes in the occurrence of spawning zones and test for correlations between maturity at age derived from otolith spawning zones and gonad maturity stages. This study shows that spawning zones likely are a universal trait of Atlantic cod and not limited to certain environments or migratory behaviors as previously proposed. Maturity at age derived from spawning zone data showed trends consistent with those from gonad examinations. However, spawning zones appear to form with a one- or two-year lag with sexual maturity, which is suspected to reflect a stabilizing of energy partitioning after the first spawning events. Our results illustrate the potential for use of spawning zones, for example in species or populations with limited available maturity data, and highlights the need for addressing the physiological processes behind their formation.
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Project description:The physical habitat used during spawning may potentially be an important factor affecting reproductive output of broadcast spawning marine fishes, particularly for species with complex, substrate-oriented mating systems and behaviors, such as Atlantic cod Gadus morhua. We characterized the habitat use and behavior of spawning Atlantic cod at two locations off the coast of southwestern Iceland during a 2-d research cruise (15-16 April 2009). We simultaneously operated two different active hydroacoustic gear types, a split beam echosounder and a dual frequency imaging sonar (DIDSON), as well as a remotely operated underwater vehicle (ROV). A total of five fish species were identified through ROV surveys: including cusk Brosme brosme, Atlantic cod, haddock Melanogrammus aeglefinus, lemon sole Microstomus kitt, and Atlantic redfish Sebastes spp. Of the three habitats identified in the acoustic surveys, the transitional habitat between boulder/lava field and sand habitats was characterized by greater fish density and acoustic target strength compared to that of sand or boulder/lava field habitats independently. Atlantic cod were observed behaving in a manner consistent with published descriptions of spawning. Individuals were observed ascending 1-5 m into the water column from the bottom at an average vertical swimming speed of 0.20-0.25 m s(-1) and maintained an average spacing of 1.0-1.4 m between individuals. Our results suggest that cod do not choose spawning locations indiscriminately despite the fact that it is a broadcast spawning fish with planktonic eggs that are released well above the seafloor.
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Project description:Stochastic environments shape life-history traits and can promote selection for risk-spreading strategies, such as bet-hedging. Although the strategy has often been hypothesized to exist for various species, empirical tests providing firm evidence have been rare, mainly due to the challenge in tracking fitness across generations. Here, we take a 'proof of principle' approach to explore whether the reproductive strategy of multiple-batch spawning constitutes a bet-hedging. We used Atlantic cod (Gadus morhua) as the study species and parameterized an eco-evolutionary model, using empirical data on size-related reproductive and survival traits. To evaluate the fitness benefits of multiple-batch spawning (within a single breeding period), the mechanistic model separately simulated multiple-batch and single-batch spawning populations under temporally varying environments. We followed the arithmetic and geometric mean fitness associated with both strategies and quantified the mean changes in fitness under several environmental stochasticity levels. We found that, by spreading the environmental risk among batches, multiple-batch spawning increases fitness under fluctuating environmental conditions. The multiple-batch spawning trait is, thus, advantageous and acts as a bet-hedging strategy when the environment is exceptionally unpredictable. Our research identifies an analytically flexible, stochastic, life-history modelling approach to explore the fitness consequences of a risk-spreading strategy and elucidates the importance of evolutionary applications to life-history diversity.
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Project description:Extreme loss of skeletal muscle overwhelms the natural regenerative capability of the body, results in permanent disability and substantial economic burden. Current surgical techniques result in poor healing, secondary injury to the autograft donor site, and incomplete recuperation of muscle function. Most current tissue engineering and regenerative strategies fail to create an adequate mechanical and biological environment that enables cell infiltration, proliferation, and myogenic differentiation. In this study, we present a nanoengineered skeletal muscle scaffold based on functionalized gelatin methacrylate (GelMA) hydrogel, optimized for muscle progenitors' proliferation and differentiation. The scaffold was capable of controlling the release of insulin-like growth factor 1 (IGF-1), an important myogenic growth factor, by utilizing the electrostatic interactions with LAPONITE® nanoclays (NCs). Physiologically relevant levels of IGF-1 were maintained during a controlled release over two weeks. The NC was able to retain 50% of the released IGF-1 within the hydrogel niche, significantly improving cellular proliferation and differentiation compared to control hydrogels. IGF-1 supplemented medium controls required 44% more IGF-1 than the comparable NC hydrogel composites. The nanofunctionalized scaffold is a viable option for the treatment of extreme muscle injuries and offers scalable benefits for translational interventions and the growing field of clean meat production.
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Project description:BACKGROUND: Daily and seasonal changes in temperature are challenges that fish within aquaculture settings cannot completely avoid, and are known to elicit complex organismal and cellular stress responses. We conducted a large-scale gene discovery and transcript expression study in order to better understand the genes that are potentially involved in the physiological and cellular aspects of stress caused by heat-shock. We used suppression subtractive hybridization (SSH) cDNA library construction and characterization to identify transcripts that were dysregulated by heat-shock in liver, skeletal muscle and head kidney of Atlantic cod. These tissues were selected due to their roles in metabolic regulation, locomotion and growth, and immune function, respectively. Fish were exposed for 3 hours to an 8 degrees C elevation in temperature, and then allowed to recover for 24 hours at the original temperature (i.e. 10 degrees C). Tissue samples obtained before heat-shock (BHS), at the cessation of heat-shock (CS), and 3, 12, and 24 hours after the cessation of heat-shock (ACS), were used for reciprocal SSH library construction and quantitative reverse transcription - polymerase chain reaction (QPCR) analysis of gene expression using samples from a group that was transferred but not heat-shocked (CT) as controls. RESULTS: We sequenced and characterized 4394 ESTs (1524 from liver, 1451 from head kidney and 1419 from skeletal muscle) from three "forward subtracted" libraries (enriched for genes up-regulated by heat-shock) and 1586 from the liver "reverse subtracted" library (enriched for genes down-regulated by heat-shock), for a total of 5980 ESTs. Several cDNAs encoding putative chaperones belonging to the heat-shock protein (HSP) family were found in these libraries, and "protein folding" was among the gene ontology (GO) terms with the highest proportion in the libraries. QPCR analysis of HSP90alpha and HSP70-1 (synonym: HSPA1A) mRNA expression showed significant up-regulation in all three tissues studied. These transcripts were more than 100-fold up-regulated in liver following heat-shock. We also identified HSP47, GRP78 and GRP94-like transcripts, which were significantly up-regulated in all 3 tissues studied. Toll-like receptor 22 (TLR22) transcript, found in the liver reverse SSH library, was shown by QPCR to be significantly down-regulated in the head kidney after heat-shock. CONCLUSION: Chaperones are an important part of the cellular response to stress, and genes identified in this work may play important roles in resistance to thermal-stress. Moreover, the transcript for one key immune response gene (TLR22) was down-regulated by heat-shock, and this down-regulation may be a component of heat-induced immunosuppression.
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Project description:In the present study, Fourier-transform infrared spectroscopy (FTIR) is investigated as a method to measure connective tissue components that are important for the quality of Atlantic cod filets (Gadus morhua L.). The Atlantic cod used in this study originated from a feeding trial, which found that fish fed a high starch diet contained relative more collagen type I, while fish fed a low starch (LS) diet contained relative more glycosaminoglycans (GAGs) in the connective tissue. FTIR spectra of pure commercial collagen type I and GAGs were acquired to identify spectral markers and compare them with FTIR spectra and images from connective tissue. Using principal component analysis, high and LS diets were separated due to collagen type I in the spectral region 1800 to 800?cm-1 . The spatial distribution of collagen type I and GAGs were further investigated by FTIR imaging in combination with immunohistochemistry. Pixel-wise correlation images were calculated between preprocessed connective tissue images and preprocessed pure components spectra of collagen type I and GAGs, respectively. For collagen, the FTIR images reveal a collagen distribution that closely resembles the collagen distribution as imaged by immunohistochemistry. For GAGs, the concentration is very low. Still, the FTIR images detect the most GAGs rich regions.
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Project description: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, and two embryonic stages (blastula, gastrula) were collected from broodstock fish and fertilized eggs. Gene expression profiles were measured in a 44?K oligo microarray consisting of 23,000 cod genes. Hundreds of differentially expressed genes (DEGs) were identified in the follicle stages investigated, implicating a continuous accumulation and degradation of polyadenylated transcripts throughout oogenesis. Very few DEGs were identified from ovulated egg to blastula, showing a more stable maternal RNA pool in early embryonic stages. The highest induction of expression was observed between blastula and gastrula, signifying the onset of zygotic transcription. During early vitellogenesis, several of the most upregulated genes are linked to nervous system signaling, suggesting increasing requirements for ovarian synaptic signaling to stimulate the rapid growth of oocytes. Highly upregulated genes during late vitellogenesis are linked to protein processing, fat metabolism, osmoregulation, and arrested meiosis. One of the genes with the highest upregulation in the ovulated egg is involved in oxidative phosphorylation, reflecting increased energy requirements during fertilization and the first rapid cell divisions of early embryogenesis. In conclusion, this study provides a large-scale presentation of the Atlantic cod's maternally controlled transcriptome in ovarian follicles through oogenesis, ovulated eggs, and early embryos.
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