Expression of melanotropin-related genes in goldfish brain, pituitary, and skin in response to background color

Poster presentado en el 17th International Congress of Comparative Endocrinology celebrado en Barcelona del 15 al 19 de julio de 2013In teleost fish, body color varies in response to changes in background color. The color is lighter in a white background than in a black background. Melanin- concentrating hormone (MCH) produced in hypothalamiand agouti signaling protein (ASP) in skins turn body color pale by aggregating pigments, while melanocyte-stimulating hormone (MSH) encoded on a proopiomelanocortin (POMC) gene disperses pigments. In the present study, we investigated the effects of a black or white background on expression levels of the genes for the hormonal peptides and corresponding receptors by real time RT-PCR in goldfish (Carassiusauratus).Peer Reviewe

Advances in comparative endocrinology : vol. VIII

Ponències presentades al 10th Congress of the Iberian Association of Comparative Endocrinology (AIEC), celebrat a la Universitat Jaume I, els dies 23 al 25 de setembre de 2015Les diverses comunicacions presentades al 10è Congrés de la Asociación Ibérica de Endocrinología Comparada (23-25 setembre 2016, Castelló) s'agrupen en aquest volum. Les intervencions han aportat els darrers avenços en àrees científiques com ara reproducció, metabolisme, estrés, resposta immune, creixement, mineralització i pigmentació...Las diversas comunicaciones presentadas en el 10º Congreso de la Asociación Ibérica de Endocrinología Comparada (23-25 septiembre 2016, Castellón) se agrupan en este volumen. Las intervenciones han aportado los últimos adelantos en áreas científicas como por ejemplo reproducción, metabolismo, estrés, respuesta inmune, crecimiento, mineralización y pigmentación...The present volume of Advances in Comparative Endocrinology collects the contributions of the participants at the 10th Congress of the Iberian Association of Comparative Endocrinology (AIEC). Eighteen years after the foundational meeting of our Association in Peñíscola, the return of this Congress to Castellón highlights the growing success of this initiative to foster the research and scientific development in the field of comparative endocrinology developed in the Iberian Peninsula. AIEC meetings have proven to be a way to keep in contact among research groups with common interests. Some of the participants in this last meeting were also present in the foundational one, others members came after and keep assisting every time. As one of the aims of AIEC has been to encourage students to participate, we are particulary proud of those young students and doctors from the first editions that have gained more permanent positions and continue participating in the AIEC meetings with new students

Pigment-dispersing activities and cortisol-releasing activities of melanocortins and their receptors in xanthophores and head kidneys of the goldfish Carassius auratus

The five subtypes of melanocortin receptors (MCRs) mediate the functions of α-melanocyte-stimulating hormone (α-MSH) and adrenocorticotropic hormone (ACTH). In fish, these hormones are involved in pigment dispersion and cortisol release, respectively. α-MSH-related peptides exhibit ACTH-like activity in certain fishes. We recently found that multiple Mcr transcripts are expressed in some cell types in the barfin flounder, which is related to regulation of α-MSH activities. Similar results were also observed for the cortisol-releasing activity of α-MSH-related peptides in the head kidney. The present study was undertaken to assess relationship between the expression of multiply expressed Mcrs and α-MSH activities using goldfish. We also determined if α-MSH-related peptides exhibit ACTH-like activity in goldfish. The transcripts of Mc1r, but not those of other subtypes, were observed in xanthophores. α-MSH, which has an acetyl group at the N-terminus, was found to disperse pigment in a dose-dependent manner in xanthophores. This potency was found to be slightly greater than that of desacetyl-α-MSH. These results support our findings that MCR has a higher affinity for α-MSH when single Mcr subtype is expressed. On the other hand, transcripts of Mc2r, but not those of other subtypes, were observed in the head kidney. ACTH1-24-stimulated cortisol release was observed in a dose-dependent manner, while α-MSH-related peptides showed no activity. It therefore appears that MC2R also acts as an ACTH-specific receptor in goldfish and that association of α-MSH-related peptides upon release of cortisol is uncommon in fishes. © 2011 Elsevier Inc.Peer Reviewe

Signal Transduction and Pathogenic Modifications at the Melanocortin-4 Receptor: A Structural Perspective

The melanocortin-4 receptor (MC4R) can be endogenously activated by binding of melanocyte-stimulating hormones (MSH), which mediates anorexigenic effects. In contrast, the agouti-related peptide (AgRP) acts as an endogenous inverse agonist and suppresses ligand-independent basal signaling activity (orexigenic effects). Binding of ligands to MC4R leads to the activation of different G-protein subtypes or arrestin and concomitant signaling pathways. This receptor is a key protein in the hypothalamic regulation of food intake and energy expenditure and naturally-occurring inactivating MC4R variants are the most frequent cause of monogenic obesity. In general, obesity is a growing problem on a global scale and is of social, medical, and economic relevance. A significant goal is to develop optimized pharmacological tools targeting MC4R without adverse effects. To date, this has not been achieved because of inter alia non-selective ligands across the five functionally different MCR subtypes (MC1-5R). This motivates further investigation of (i) the three-dimensional MC4R structure, (ii) binding mechanisms of various ligands, and (iii) the molecular transfer process of signal transduction, with the aim of understanding how structural features are linked with functional-physiological aspects. Unfortunately, experimentally elucidated structural information is not yet available for theMC receptors, a group of class A G-protein coupled receptors (GPCRs). We, therefore, generated MC4R homology models and complexes with interacting partners to describe approximate structural properties associated with signaling mechanisms. In addition, molecular insights from pathogenic mutations were incorporated to discriminate more precisely their individual malfunction of the signal transfer mechanism

Agouti overexpression in a transgenic model regulates integrity, permeability and electrogenic amino acid transport in zebrafish intestine

Overexpression of asip1 in transgenic zebrafish disrupts dorsoventral pigment pattern in addition to increasing food intake levels and linear growth. A higher feed intake is unnecessary in transgenic fish to enable larger and heavier growth. A plausible explanation may rely on the enhanced feeding efficiency mediated by improved nutrient absorption in transgenic animals. To test this hypothesis, wide scope transcriptomic techniques were used to elucidate the potential pathways involved in the enhanced nutrient absorption and intestinal epithelium permeability/integrity. In addition, the electrogenic capacity for amino acid transport was analysed. Transcriptomic analysis reveal that amino acid, monocarboxylates, ionic and vitamin transmembrane transporters were substantially modified. Enrichment analysis also revealed an inhibition of intestinal lipid metabolism and down-regulation of KEGG pathways related to membrane integrity suggesting augmented intestinal laxity that may enhance paracellular transport. Electrophysiological experiments carried out in Ussing chambers show that asip1 overexpression decrease membraned tissue resistance (Rt), indicating a modification of the intestinal barrier function in ASIP1 transgenic animals. Similarly, paracellular permeability was higher in transgenic zebrafish. Both the decrease in Rt and the increase in permeability point to an ASIP1-dependent decrease in the tissue barrier function. Electrogenic amino acid transport was also enhanced in transgenic animals providing strong indication that ASIP1 fish can extract more amino acids from their diet at similar feeding levels. Both transcriptomic and electrophysiological results suggest that asip1-overexpressing zebrafish display improved nutrient absorption and by extension a higher feed efficiency which explains enhanced growth in the absence of augmented food intake. The enhanced growth of ASIP1 zebrafish potentially mediated by improved nutrient uptake and feed efficiency suggests that the melanocortin system, specifically asip1 overexpression, is a potential target for the development of genetically engineered fish displaying improved performance and no differential lipid accumulation.info:eu-repo/semantics/publishedVersio

Role of the Melanocortin System in Gonadal Steroidogenesis of Zebrafish

In teleost, as in other vertebrates, stress affects reproduction. A key component of the stress response is the pituitary secretion of the adrenocorticotropic hormone (ACTH), which binds to the melanocortin 2 receptor (MC2R) in the adrenal glands and activates cortisol biosynthesis. In zebrafish, Mc2r was identified in male and female gonads, while ACTH has been shown to have a physiological role in modulating reproductive activity. In this study, the hypothesis that other melanocortins may also affect how the zebrafish gonadal function is explored, specifically steroid biosynthesis, given the presence of members of the melanocortin signaling system in zebrafish gonads. Using cell culture, expression analysis, and cellular localization of gene expression, our new observations demonstrated that melanocortin receptors, accessory proteins, antagonists, and agonists are expressed in both the ovary and testis of zebrafish (n = 4 each sex). Moreover, melanocortin peptides modulate both basal and gonadotropin-stimulated steroid release from zebrafish gonads (n = 15 for males and n = 50 for females). In situ hybridization in ovaries (n = 3) of zebrafish showed mc1r and mc4r in follicular cells and adjacent to cortical alveoli in the ooplasm of previtellogenic and vitellogenic oocytes. In zebrafish testes (n = 3), mc4r and mc1r were detected exclusively in germ cells, specifically in spermatogonia and spermatocytes. Our results suggest that melanocortins are, directly or indirectly, involved in the endocrine control of vitellogenesis in females, through modulation of estradiol synthesis via autocrine or paracrine actions in zebrafish ovaries. Adult zebrafish testes were sensitive to low doses of ACTH, eliciting testosterone production, which indicates a potential role of this peptide as a paracrine regulator of testicular function.publishedVersio

Role of the Melanocortin System in Gonadal Steroidogenesis of Zebrafish

In teleost, as in other vertebrates, stress affects reproduction. A key component of the stress response is the pituitary secretion of the adrenocorticotropic hormone (ACTH), which binds to the melanocortin 2 receptor (MC2R) in the adrenal glands and activates cortisol biosynthesis. In zebrafish, Mc2r was identified in male and female gonads, while ACTH has been shown to have a physiological role in modulating reproductive activity. In this study, the hypothesis that other melanocortins may also affect how the zebrafish gonadal function is explored, specifically steroid biosynthesis, given the presence of members of the melanocortin signaling system in zebrafish gonads. Using cell culture, expression analysis, and cellular localization of gene expression, our new observations demonstrated that melanocortin receptors, accessory proteins, antagonists, and agonists are expressed in both the ovary and testis of zebrafish (n = 4 each sex). Moreover, melanocortin peptides modulate both basal and gonadotropin-stimulated steroid release from zebrafish gonads (n = 15 for males and n = 50 for females). In situ hybridization in ovaries (n = 3) of zebrafish showed mc1r and mc4r in follicular cells and adjacent to cortical alveoli in the ooplasm of previtellogenic and vitellogenic oocytes. In zebrafish testes (n = 3), mc4r and mc1r were detected exclusively in germ cells, specifically in spermatogonia and spermatocytes. Our results suggest that melanocortins are, directly or indirectly, involved in the endocrine control of vitellogenesis in females, through modulation of estradiol synthesis via autocrine or paracrine actions in zebrafish ovaries. Adult zebrafish testes were sensitive to low doses of ACTH, eliciting testosterone production, which indicates a potential role of this peptide as a paracrine regulator of testicular function

Experiments on zebrafish using mini robot fish prototypes to identify stressors

This paper describes the behavioural tests carried out with real fish to study their behaviour and stress against the different prototypes of mini-robot fish with the aim of identifying stressors and reducing them when designing future robots for aquaculture.Peer Reviewe

Food Intake Regulation

Feeding is the way in which heterotroph animals incorporate organic nitrogen and carbon for growth. Most heterotroph organisms also obtain energy in this way. Together with reproduction, feeding is a key function in evolution since metabolic energy obtainment and storage make an important contribution to survival rates. This evolutionary relevance suggests that feeding regulation should be highly redundant and conservative. Redundancy confers backup systems on functional regulation, which, while preserving the function, leads to greater complexity of the same, increasing the diffi culty of its study. On the other hand, evolutionary conservation of regulatory mechanisms makes fi sh an excellent model for studying mammalian species. However, the opposite is also true, that mammalian species are an excellent model for fi sh and fi sh research can take full advantage of previous experimental effort focusing on mammalian obesityPeer reviewe

Dietary discrimination of organoleptic cues in gilthead seabream (Sparus aurata)

Self-feeding and dualchoice systems have been extensively used to study animal feeding behaviour and food preferences but are still little explored in fish species. Seabream (Sparus aurata) is an important farmed Mediterranean species, but little is known regarding its taste preferences, including its capacity to discriminate diets using sensory (olfactory and/or gustative) traits. With this in mind, the capability of gilthead seabream to discriminate feed organoleptic qualities was investigated by presenting the fish with a dual choice of feeds in a self-feeding system. Furthermore, two consecutive trials were performed with the same group of fish during summer or autumn (i.e., at different water temperatures), to assess whether the feeding behavior might be affected by the fishes' physiological state or environmental parameters.Peer reviewe