Coordinated gene expression during gilthead sea bream skeletogenesis and its disruption by nutritional hypervitaminosis A

Background: Vitamin A (VA) has a key role in vertebrate morphogenesis, determining body patterning and growth through the control of cell proliferation and differentiation processes. VA regulates primary molecular pathways of those processes by the binding of its active metabolite (retinoic acid) to two types of specific nuclear receptors: retinoic acid receptors (RARs) and retinoid X receptors (RXRs), which promote transcription of downstream target genes. This process is well known in most of higher vertebrates; however, scarce information is available regarding fishes. Therefore, in order to gain further knowledge of fish larval development and its disruption by nutritional VA imbalance, the relative expression of some RARs and RXRs, as well as several genes involved in morpho- and skeletogenesis such as peroxisome proliferator-activated receptors (PPARA, PPARB and PPARG); retinol-binding protein (RBP); insulin-like growth factors I and II (IGF1 and IGF2, respectively); bone morphogenetic protein 2 (Bmp2); transforming growth factor beta-1 (TGFB1); and genes encoding different extracellular matrix (ECM) proteins such as matrix Gla protein (mgp), osteocalcin (bglap), osteopontin (SPP1), secreted protein acidic and rich in cysteine (SPARC) and type I collagen alpha 1 chain (COL1A1) have been studied in gilthead sea bream. Results: During gilthead sea bream larval development, specific expression profiles for each gene were tightly regulated during fish morphogenesis and correlated with specific morphogenetic events and tissue development. Dietary hypervitaminosis A during early larval development disrupted the normal gene expression profile for genes involved in RA signalling (RARA), VA homeostasis (RBP) and several genes encoding ECM proteins that are linked to skeletogenesis, such as bglap and mgp. Conclusions: Present data reflects the specific gene expression patterns of several genes involved in larval fish RA signalling and skeletogenesis; and how specific gene disruption induced by a nutritional VA imbalance underlie the skeletal deformities. Our results are of basic interest for fish VA signalling and point out some of the potential molecular players involved in fish skeletogenesis. Increased incidences of skeletal deformities in gilthead sea bream fed with hypervitaminosis A were the likely ultimate consequence of specific gene expression disruption at critical development stages

Salinity reduction benefits European eel larvae: Insights at the morphological and molecular level

European eel (Anguilla anguilla) is a euryhaline species, that has adapted to cope with both, hyper- and hypo-osmotic environments. This study investigates the effect of salinity, from a morphological and molecular point of view on European eel larvae reared from 0 to 12 days post hatch (dph). Offspring reared in 36 practical salinity units (psu; control), were compared with larvae reared in six scenarios, where salinity was decreased on 0 or 3 dph and in rates of 1, 2 or 4 psu/day, towards iso-osmotic conditions. Results showed that several genes relating to osmoregulation (nkcc2α, nkcc2β, aqp1dup, aqpe), stress response (hsp70, hsp90), and thyroid metabolism (thrαA, thrαB, thrβB, dio1, dio2, dio3) were differentially expressed throughout larval development, while nkcc1α, nkcc2β, aqp3, aqp1dup, aqpe, hsp90, thrαA and dio3 showed lower expression in response to the salinity reduction. Moreover, larvae were able to keep energy metabolism related gene expression (atp6, cox1) at stable levels, irrespective of the salinity reduction. As such, when reducing salinity, an energy surplus associated to reduced osmoregulation demands and stress (lower nkcc, aqp and hsp expression), likely facilitated the observed increased survival, improved biometry and enhanced growth efficiency. Additionally, the salinity reduction decreased the amount of severe deformities such as spinal curvature and emaciation but also induced an edematous state of the larval heart, resulting in the most balanced mortality/deformity ratio when salinity was decreased on 3 dph and at 2 psu/day. However, the persistency of the pericardial edema and if or how it represents an obstacle in further larval development needs to be further clarified. In conclusion, this study clearly showed that salinity reduction regimes towards iso-osmotic conditions facilitated the European eel pre-leptocephalus development and revealed the existence of highly sensitive and regulated osmoregulation processes at such early life stage of this species

Effect of thermal and nutritional conditions on fatty acid metabolism and oxidative stress response in juvenile European sea bass (Dicentrarchus labrax)

Coastal nursery areas are subjected to a wide range of natural and anthropogenic stressors, including global warming, which indirectly influence trophic food webs. A global rarefaction of n-3 polyunsaturated fatty acids (PUFA) in trophic networks is in progress. The aim of this study was to assess the effect of a reduction in the dietary availability of n-3 PUFA on some molecular and biochemical parameters related to lipid metabolism and oxidative stress response in juvenile European sea bass (Dicentrarchus labrax) raised at two temperatures (15 °C and 20 °C). Fish were fed for five months with a reference diet (RD; 1.65% n-3 PUFA on a dry matter basis, DM), used as a proxy of trophic networks where n-3 PUFA is plentiful, and a lower n-3 PUFA diet (LD; 0.73% n-3 PUFA DM), designed to mimic a decrease in n-3 PUFA resulting from global changes (the n-3 PUFA levels tested remained above the nutritional minimum required for this species). Results showed that diet did not affect the hepatic expression of some mRNA coding for transcriptional factors involved in regulating the metabolic pathways related to fatty acid bioconversion. Although our molecular analysis was limited to transcript expression, these data suggest the presence of a threshold in the nutritional supply of PUFA above which the activation of these molecular pathways does not occur. However, the expression for most of the transcripts tested was up-regulated at 20 °C. Despite the high peroxidation index in fish fed RD, very few modifications of the oxidative stress response were associated with diet. At 20 °C, an increase of the enzymatic antioxidant response was observed, but there was no correlation with the peroxidation index or malondialdehyde products

The Korowai Framework: Assessing GE through the Values the ART Confederation Associates with Ngarara

The aim of this thesis is to assess genetic engineering (GE) through the values that the Confederation of Te Ati Awa, Ngati Raukawa ki te tonga and Ngati Toarangatira (the ART Confederation) associates with ngarara. The Korowai Framework was developed to conduct this assessment. Interviews were conducted with 14 participants from across the ART Confederation on the values they associate with ngarara and their interpretations of GE. The values associated with ngarara that were identified in the interviews, were used constitute the kaupapa of the Korowai Framework. The key values identified are: mauri, whakapapa, tohu, tapu, and kaitiakitanga. It emerged from the interviews that ngarara appeal to us to be conscious of our intricately bound connection to and dependency on living systems. The assessment through the Korowai Framework found that the outcomes of GE do not uphold the values associated with ngarara. Participants articulated significant concerns that GE confounds the ART Confederation's control over their relationship with the world around them. This thesis has demonstrated that the Korowai Framework can be used as a tool for the Confederation to get to the decision making table with a comprehensive evidence based understanding of the people's position on GE from which they can negotiate. It demonstrates that robust and legitimate assessment of GE can be conducted using theories, methodologies, kaupapa, tikanga, and frameworks that are specific to the ART Confederation

Effects of the total replacement of fish-based diet with plant-based diet on the hepatic transcriptome of two European sea bass (Dicentrarchus labrax) half-sibfamilies showing different growth rates with the plant-based diet

Background: Efforts towards utilisation of diets without fish meal (FM) or fish oil (FO) in finfish aquaculture have been being made for more than two decades. Metabolic responses to substitution of fishery products have been shown to impact growth performance and immune system of fish as well as their subsequent nutritional value, particularly in marine fish species, which exhibit low capacity for biosynthesis of long-chain poly-unsaturated fatty acids (LC-PUFA). The main objective of the present study was to analyse the effects of a plant-based diet on the hepatic transcriptome of European sea bass (Dicentrarchus labrax). Results: We report the first results obtained using a transcriptomic approach on the liver of two half-sibfamilies of the European sea bass that exhibit similar growth rates when fed a fish-based diet (FD), but significantly different growth rates when fed an all-plant diet (VD). Overall gene expression was analysed using oligo DNA microarrays (GPL9663). Statistical analysis identified 582 unique annotated genes differentially expressed between groups of fish fed the two diets, 199 genes regulated by genetic factors, and 72 genes that exhibited diet-family interactions. The expression of several genes involved in the LC-PUFA and cholesterol biosynthetic pathways was found to be up-regulated in fish fed VD, suggesting a stimulation of the lipogenic pathways. No significant diet-family interaction for the regulation of LC-PUFA biosynthesis pathways could be detected by microarray analysis. This result was in agreement with LC-PUFA profiles, which were found to be similar in the flesh of the two half-sibfamilies. In addition, the combination of our transcriptomic data with an analysis of plasmatic immune parameters revealed a stimulation of complement activity associated with an immunodeficiency in the fish fed VD, and different inflammatory status between the two half-sibfamilies. Biological processes related to protein catabolism, amino acid transaminations, RNA splicing and blood coagulation were also found to be regulated by diet, while the expression of genes involved in protein and ATP synthesis differed between the half-sibfamilies. Conclusions: Overall, the combined gene expression, compositional and biochemical studies demonstrated a large panel of metabolic and physiological effects induced by total substitution of both FM and FO in the diets of European sea bass and revealed physiological characteristics associated with the two half-sibfamilies

CLONAGE ET EXPRESSION DES RECEPTEURS A LA MELATONINE CHEZ LA TRUITE ARC-EN-CIEL (ONCORHYNCHUS MYKISS) (CONTRIBUTION A L'ETUDE DES MECANISMES D'INTEGRATION DU MESSAGE PHOTOPERIODIQUE)

CHEZ LES VERTEBRES, LA MELATONINE, PRINCIPALE HORMONE SECRETEE PAR LA GLANDE PINEALE DURANT LA PHASE NOCTURNE, EST CONSIDEREE COMME ETANT LE PRINCIPAL ACTEUR IMPLIQUE DANS L'INTEGRATION ET LA TRANSMISSION DU MESSAGE PHOTOPERIODIQUE CONTROLANT LES ACTIVITES RYTHMIQUES ET EN PARTICULIER LA REPRODUCTION SAISONNIERE. DANS LE BUT DE MIEUX APPREHENDER LES MECANISMES MIS EN UVRE DANS L'INTEGRATION DU MESSAGE PHOTOPERIODIQUE CHEZ LA TRUITE ARC-EN-CIEL, NOUS AVONS ENTREPRIS L'ETUDE DES SITES D'EXPRESSION DES RECEPTEURS A LA MELATONINE DANS LES TISSUS PERIPHERIQUES PAR RT-PCR, AINSI QUE DANS LE SYSTEME NERVEUX CENTRAL PAR HYBRIDATION IN SITU. LE CLONAGE ENTIER DU RECEPTEUR A LA MELATONINE MEL1A AINSI QUE LE CLONAGE PARTIEL DE MEL1B ONT ETE REALISES. L'ETUDE PAR RT-PCR A PERMIS DE DETECTER UNE EXPRESSION DIFFERENTIELLE DE CES DEUX SOUS-TYPES DE RECEPTEURS DANS DE NOMBREUX TISSUS, INDIQUANT PAR AILLEURS DE MULTIPLES SITES D'ACTION DE L'HORMONE. L'EXPRESSION DETECTEE DANS L'HYPOPHYSE AINSI QUE LES EXPERIENCES REALISEES SUR CULTURE DE CELLULES HYPOPHYSAIRES SUGGERENT UN EFFET DIRECT DE LA MELATONINE SUR LES GONADOTROPES. LES SITES D'EXPRESSION AU NIVEAU CENTRAL CONCERNENT ESSENTIELLEMENT DES STRUCTURES SENSORIELLES A COMPETENCES VISUELLES (AIRE PRETECTALE, TOITS OPTIQUES, CERVELET). UNE FAIBLE EXPRESSION DES RECEPTEURS A LA MELATONINE A EGALEMENT PU ETRE OBSERVEE DANS LA REGION PREOPTIQUE AINSI QUE DANS L'HYPOTHALAMUS MEDIOBASAL SUGGERANT DES RELATIONS POSSIBLES ENTRE LES CENTRES D'INTEGRATION DU MESSAGE PHOTOPERIODIQUE ET LES CIRCUITS NEUROENDOCRINIENS IMPLIQUES DANS LA FONCTION DE REPRODUCTION. L'HYPOTHESE SELON LAQUELLE LA MELATONINE POURRAIT INFLUENCER L'EXPRESSION DU RECEPTEUR A L'OESTRADIOL (RTER) A ETE TESTEE, CEPENDANT AUCUNE INFLUENCE DE LA MELATONINE SUR L'EXPRESSION HEPATIQUE DE RTER N'A PU ETRE MISE EN EVIDENCE. DANS LE BUT D'IDENTIFIER DES STRUCTURES CEREBRALES POUVANT JOUER LE ROLE D'HORLOGE BIOLOGIQUE, NOUS AVONS ENTREPRIS LE CLONAGE ET L'ETUDE DES SITES D'EXPRESSION D'UN GENE HORLOGE, CLOCK. EN DEPIT DU FAIT QUE NOUS N'AVONS PAS DETECTE DE VARIATION CIRCADIENNE DES MESSAGERS DE CLOCK ET DES RECEPTEURS A LA MELATONINE, LA COEXPRESSION DE CES DEUX FACTEURS DANS L'AIRE PRETECTALE ET LES TOITS OPTIQUES SUGGERE L'EXISTENCE D'ORGANISATIONS CELLULAIRES POUVANT JOUER LE ROLE D'HORLOGE INTERNE DANS LE SYSTEME NERVEUX CENTRAL DE TRUITE ARC-EN-CIEL.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Fish facing global change: are early stages the lifeline?

International audienceThe role of phenotypic plasticity in the acclimation and adaptive potential of an organism to global change is not currently accounted for in prediction models. The high plasticity of marine fishes is mainly attributed to their early stages, during which morphological, structural and behavioural 'functions are particularly sensitive to environmental constraints. This developmental plasticity can determine later physiological performances and fitness, and may further affect population dynamics and ecosystem functioning. This review asks the essential question of what role early stages play in the ability of fish to later cope with the effects of global change, considering three key environmental factors (temperature, hypoxia and acidification). After having identified the carry-over effects of early exposure reported in the literature, we propose areas that we believe warrant the most urgent attention for further research to better understand the role of developmental plasticity in the responses of marine organisms to global change

Response to visual and mechano-acoustic predator cues is robust to ocean warming and acidification and is highly variable in European sea bass

Predator-prey interactions and, especially, the success of anti-predator responses are modulated by the sensory channels of vision, olfaction, audition and mechanosensation. If climate change alters fish sensory ability to avoid predation, community dynamics can be affected. We investigated whether mid-duration exposure to warming and/or acidification alters behavioural response to visual or mechano-acoustic predator cues in juvenile Dicentrarchus labrax. We measured kinematic variables before and after a visual or a mechano-acoustic challenge which mimicked an overflying bird shadow or a bird swoop attack, respectively. Due to large interindividual variability in responses before cue presentation, fish were categorized as slow and fast to account for baseline individual variability. Treatment did not impact kinematic variables as both slow and fast fish of every treatment elicited precautionary and escape responses. Interestingly, even slow fish swam as fast as fast fish after the cue, suggesting that regardless of initial category, fish managed to escape facing a danger. Anti-predator response varied according to the level of threat to survival with greater responses elicited after the swoop attack. Although wild juvenile sea bass aggregate in schools, school dynamics rely on single leaders which highlights the importance of the variability in individual behaviours. We demonstrated that anti-predator response in juvenile D. labrax is robust to mid-duration exposure to independent and combined effects of warming and acidification. If robustness is confirmed over long-duration, it could provide D. labrax with an evolutionary advantage in the future ocean, where cue transmission through changing environments can further modulate cue perception and predator-prey interactions

Transcriptional analysis of spermatogenesis regulation using trout cDNA arrays

International audienc

Transcriptional analysis of spermatogenesis regulation using trout cDNA arrays

International audienc