Molecular evolution of the neuropeptide Y (NPY) family of peptides: cloning of three NPY-related peptides from the sea bass (Dicentrarchus labrax)

Neuropeptide Y receptor Y2 (npy2r) deficiency reduces anxiety and increases food intake in Japanese medaka (Oryzias latipes)

Neuropeptide Y receptor Y2 (npy2r) is an important receptor gene involved in anxiety and feeding regulation in mammals. Since NPY receptors have different receptor gene deletions in mammals and teleost fish, it is not clear whether npy2r has the similar function in fish as in mammals. In this study, we used the CRISPR/Cas9 system to establish npy2r-deficient medaka (Oryzias latipes). Unexpectedly, the deletion of npy2r resulted in the npy2r +/- medaka were all-male, therefore, npy2r homozygous mutant lines could not be established. The deletion of npy2r increased the food intake in medaka, and the expression levels of appetite stimulating genes (agrp, npy) increased significantly, while the expression levels of anorexia factors (cck, pomc) decreased significantly. Moreover, the absence of npy2r significantly increased the total length and body weight of medaka. The mirror test and open field test showed that npy2r +/- medaka improved sociability and reduced anxiety-like behavior, qRT-PCR analysis showed that the expression levels of anxiety related genes (th1, th2, gr1, gr2, and mr) in npy2r +/- medaka were significantly decreased. So far, this is the first npy2r gene knockout model established in fish and demonstrates that npy2r plays an important role in the regulation of reproduction, feeding and anxiety in fish.

The Interplay between Central and Peripheral Systems in Feed Intake Regulation in European Seabass (Dicentrarchus labrax) Juveniles

The present study aimed to evaluate the effects of feeding or feed deprivation on the orexigenic and anorexigenic responses at the central (whole brain) and peripheral (anterior and posterior intestine, stomach, and liver) system levels in European seabass. For this purpose, a group of fish (208 g) was fed a single meal daily for 8 days (fed group) and another group was feed-deprived for 8 days (unfed group). Compared to the fed group, in the whole brain, feed deprivation did not induce changes in npy, agrp1, and cart2 expression, but increased agrp2 and pomc1 expression. In the anterior intestine, feed deprivation increased cck expression, while in the posterior intestine, the npy expression increased and pyyb decreased. In the stomach, the ghr expression decreased regardless of the feeding status. The hepatic lep expression increased in the unfed fish. The present results suggest a feed intake regulation mechanism in European seabass similar to that observed in other teleosts.

Crystal structures of human neuropeptide Y (NPY) and peptide YY (PYY)

Neuropeptide Y (NPY), peptide YY (PYY) and pancreatic polypeptide (PP) form the evolutionarily conserved pancreatic polypeptide family. While the fold is widely utilized in nature, crystal structures remain elusive, particularly for the human forms, with only the structure of a distant avian form of PP reported. Here we utilize a crystallization chaperone (antibody Fab fragment), specifically recognizing the amidated peptide termini, to solve the structures of human NPY and human PYY. Intriguingly, and despite limited sequence identity (~50%), the structure of human PYY closely resembles that of avian PP, highlighting the broad structural conservation of the fold throughout evolution. Specifically, the PYY structure is characterized by a C-terminal amidated α-helix, preceded by a backfolded poly-proline N-terminus, with the termini in close proximity to each other. In contrast, in the structure of human NPY the N-terminal component is disordered, while the helical component of the peptide is observed in a four-helix bundle type arrangement, consistent with a propensity for multimerization suggested by NMR studies.

Echinoderms provide missing link in the evolution of PrRP/sNPF-type neuropeptide signalling

Neuropeptide signalling systems comprising peptide ligands and cognate receptors are evolutionarily ancient regulators of physiology and behaviour. However, there are challenges associated with determination of orthology between neuropeptides in different taxa. Orthologs of vertebrate neuropeptide-Y (NPY) known as neuropeptide-F (NPF) have been identified in protostome invertebrates, whilst prolactin-releasing peptide (PrRP) and short neuropeptide-F (sNPF) have been identified as paralogs of NPY/NPF in vertebrates and protostomes, respectively. Here we investigated the occurrence of NPY/NPF/PrRP/sNPF-related signalling systems in a deuterostome invertebrate phylum - the Echinodermata. Analysis of transcriptome/genome sequence data revealed loss of NPY/NPF-type signalling, but orthologs of PrRP-type neuropeptides and sNPF/PrRP-type receptors were identified in echinoderms. Furthermore, experimental studies revealed that the PrRP-type neuropeptide pQDRSKAMQAERTGQLRRLNPRF-NH₂ is a potent ligand for a sNPF/PrRP-type receptor in the starfish Asterias rubens. Our findings indicate that PrRP-type and sNPF-type signalling systems are orthologous and originated as a paralog of NPY/NPF-type signalling in Urbilateria.

Strategies for the Identification of Bioactive Neuropeptides in Vertebrates

Neuropeptides exert essential functions in animal physiology by controlling e.g., reproduction, development, growth, energy homeostasis, cardiovascular activity and stress response. Thus, identification of neuropeptides has been a very active field of research over the last decades. This review article presents the various methods used to discover novel bioactive peptides in vertebrates. Initially identified on the basis of their biological activity, some neuropeptides have also been discovered for their ability to bind/activate a specific receptor or based on their biochemical characteristics such as C-terminal amidation which concerns half of the known neuropeptides. More recently, sequencing of the genome of many representative species has facilitated peptidomic approaches using mass spectrometry and in silico screening of genomic libraries. Through these different approaches, more than a hundred of bioactive neuropeptides have already been identified in vertebrates. Nevertheless, researchers continue to find new neuropeptides or to identify novel functions of neuropeptides that had not been detected previously, as it was recently the case for nociceptin.

Arctic charr brain transcriptome strongly affected by summer seasonal growth but only subtly by feed deprivation

Background

The Arctic charr (Salvelinus alpinus) has a highly seasonal feeding cycle that comprises long periods of voluntary fasting and a short but intense feeding period during summer. Therefore, the charr represents an interesting species for studying appetite-regulating mechanisms in fish.

Results

In this study, we compared the brain transcriptomes of fed and feed deprived charr over a 4 weeks trial during their summer feeding season. Despite prominent differences in body condition between fed and feed deprived charr at the end of the trial, feed deprivation affected the brain transcriptome only slightly. In contrast, the transcriptome differed markedly over time in both fed and feed deprived charr, indicating strong shifts in basic cell metabolic processes possibly due to season, growth, temperature, or combinations thereof. The GO enrichment analysis revealed that many biological processes appeared to change in the same direction in both fed and feed deprived fish. In the feed deprived charr processes linked to oxygen transport and apoptosis were down- and up-regulated, respectively. Known genes encoding for appetite regulators did not respond to feed deprivation. Gene expression of Deiodinase 2 (DIO2), an enzyme implicated in the regulation of seasonal processes in mammals, was lower in response to season and feed deprivation. We further found a higher expression of VGF (non-acronymic) in the feed deprived than in the fed fish. This gene encodes for a neuropeptide associated with the control of energy metabolism in mammals, and has not been studied in relation to regulation of appetite and energy homeostasis in fish.

Conclusions

In the Arctic charr, external and endogenous seasonal factors for example the increase in temperature and their circannual growth cycle, respectively, evoke much stronger responses in the brain than 4 weeks feed deprivation. The absence of a central hunger response in feed deprived charr give support for a strong resilience to the lack of food in this high Arctic species. DIO2 and VGF may play a role in the regulation of energy homeostasis and need to be further studied in seasonal fish.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5874-z) contains supplementary material, which is available to authorized users.

Nutrient Regulation of Endocrine Factors Influencing Feeding and Growth in Fish

Endocrine factors regulate food intake and growth, two interlinked physiological processes critical for the proper development of organisms. Somatic growth is mainly regulated by growth hormone (GH) and insulin-like growth factors I and II (IGF-I and IGF-II) that act on target tissues, including muscle, and bones. Peptidyl hormones produced from the brain and peripheral tissues regulate feeding to meet metabolic demands. The GH-IGF system and hormones regulating appetite are regulated by both internal (indicating the metabolic status of the organism) and external (environmental) signals. Among the external signals, the most notable are diet availability and diet composition. Macronutrients and micronutrients act on several hormone-producing tissues to regulate the synthesis and secretion of appetite-regulating hormones and hormones of the GH-IGF system, eventually modulating growth and food intake. A comprehensive understanding of how nutrients regulate hormones is essential to design diet formulations that better modulate endogenous factors for the benefit of aquaculture to increase yield. This review will discuss the current knowledge on nutritional regulation of hormones modulating growth and food intake in fish.

Structural and functional characterization of peptide YY on feeding in Schizothorax davidi

Several studies have demonstrated that the neuropeptide peptide YY (PYY) plays an important role in feeding in mammals and fish. However, thus far, the feeding regulation function of PYY in Schizothorax davidi has not been well understood. Here, we identified the full-length cDNA sequence of PYY in S. davidi for the first time. S. davidi PYY contains 803 bp nucleotides including a 328 bp 3' untranslated region (UTR), a 181 bp 5' UTR, and a 294 bp open reading frame encoding a peptide of 97 amino acids. S. davidi PYY expression was observed in almost all tissues, with the highest expression detected in the hypothalamus. PYY mRNA expression in the hypothalamus was significantly elevated after a meal (P < 0.01), and significantly decreased after fasting (P < 0.01). PYY expression levels were increased sharply following refeeding after 9 days (P < 0.01), suggesting that it might function as a satiety factor in S. davidi.

New immunomodulatory role of neuropeptide Y (NPY) in Salmo salar leucocytes

Neuropeptide Y (NPY) plays different roles in mammals such as: regulate food intake, memory retention, cardiovascular functions, and anxiety. It has also been shown in the modulation of chemotaxis, T lymphocyte differentiation, and leukocyte migration. In fish, NPY expression and functions have been studied but its immunomodulatory role remains undescribed. This study confirmed the expression and synthesis of NPY in S. salar under inflammation, and validated a commercial antibody for NPY detection in teleost. Additionally, immunomodulatory effects of NPY were assayed in vitro and in vivo. Phagocytosis and superoxide anion production in leukocytes and SHK cells were induced under stimulation with a synthetic peptide. IL-8 mRNA was selectively and strongly induced in the spleen, head kidney, and isolated cells, after in vivo challenge with NPY. All together suggest that NPY is expressed in immune tissues and modulates the immune response in teleost fish.

Hypothalamic Integration of Metabolic, Endocrine, and Circadian Signals in Fish: Involvement in the Control of Food Intake

The regulation of food intake in fish is a complex process carried out through several different mechanisms in the central nervous system (CNS) with hypothalamus being the main regulatory center. As in mammals, a complex hypothalamic circuit including two populations of neurons: one co-expressing neuropeptide Y (NPY) and Agouti-related peptide (AgRP) and the second one population co-expressing pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) is involved in the integration of information relating to food intake control. The production and release of these peptides control food intake, and the production results from the integration of information of different nature such as levels of nutrients and hormones as well as circadian signals. The present review summarizes the knowledge and recent findings about the presence and functioning of these mechanisms in fish and their differences vs. the known mammalian model.

Neuropeptide Y in Alcohol Addiction and Affective Disorders

Neuropeptide Y (NPY), a neuropeptide highly conserved throughout evolution, is present at high levels in the central nervous system (CNS), as well as in peripheral tissues such as the gut and cardiovascular system. The peptide exerts its effects via multiple receptor subtypes, all belonging to the G-protein-coupled receptor superfamily. Of these subtypes, the Y1 and the Y2 are the most thoroughly characterized, followed by the Y5 subtype. NPY and its receptors have been shown to be of importance in central regulation of events underlying, for example, affective disorders, drug/alcohol use disorders, and energy homeostasis. Furthermore, within the CNS, NPY also affects sleep regulation and circadian rhythm, memory function, tissue growth, and plasticity. The potential roles of NPY in the etiology and pathophysiology of mood and anxiety disorders, as well as alcohol use disorders, have been extensively studied. This focus was prompted by early indications for an involvement of NPY in acute responses to stress, and, later, also data pointing to a role in alterations within the CNS during chronic, or repeated, exposure to adverse events. These functions of NPY, in addition to the peptide's regulation of disease states, suggest that modulation of the activity of the NPY system via receptor agonists/antagonists may be a putative treatment mechanism in affective disorders as well as alcohol use disorders. In this review, we present an overview of findings with regard to the NPY system in relation to anxiety and stress, acute as well as chronic; furthermore we discuss post-traumatic stress disorder and, in part depression. In addition, we summarize findings on alcohol use disorders and related behaviors. Finally, we briefly touch upon genetic as well as epigenetic mechanisms that may be of importance for NPY function and regulation. In conclusion, we suggest that modulation of NPY-ergic activity within the CNS, via ligands aimed at different receptor subtypes, may be attractive targets for treatment development for affective disorders, as well as for alcohol use disorders.

Evolutionary and Comparative Genomics to Drive Rational Drug Design, with Particular Focus on Neuropeptide Seven-Transmembrane Receptors

Seven transmembrane receptors (7TMRs), also known as G protein-coupled receptors, are popular targets of drug development, particularly 7TMR systems that are activated by peptide ligands. Although many pharmaceutical drugs have been discovered via conventional bulk analysis techniques the increasing availability of structural and evolutionary data are facilitating change to rational, targeted drug design. This article discusses the appeal of neuropeptide-7TMR systems as drug targets and provides an overview of concepts in the evolution of vertebrate genomes and gene families. Subsequently, methods that use evolutionary concepts and comparative analysis techniques to aid in gene discovery, gene function identification, and novel drug design are provided along with case study examples.

Mass spectrometry-assisted confirmation of the inability of dipeptidyl peptidase-4 to cleave goldfish peptide YY(1-36) and the lack of anorexigenic effects of peptide YY(3-36) in goldfish (Carassius auratus)

Dipeptidyl peptidase-4 (DPP4) is a serine protease of great interest because it has been shown to modulate the activity of several peptidergic factors including peptide YY (PYY) and glucagon-like peptide-1/2. While PYY(1-36) is orexigenic in mammals, PYY(3-36) recently garnered interest as a potent anorexigen. In silico phylogenetic analysis found that the DPP4 cleavage sites are absent in fish PYY sequences. However, no studies were conducted to show that indeed PYY(3-36) is not produced by DPP4 in fish. If DPP4 does not cleave PYY(1-36), is PYY(3-36) an anorexigen in fish? The objectives of this research were to (1) test whether DPP4 cleaves goldfish PYY(1-36) and (2) determine whether PYY(3-36) is an anorexigen in goldfish. First, we identified the highly conserved catalytic region of DPP4 in goldfish. Abundant expression of DPP4 mRNA was found within the gastrointestinal tract. We also report the first MALDI-MS cleavage analysis of DPP4 effects on PYY(1-36) in a non-mammalian vertebrate. Our novel results indicate that DPP4 is unable to cleave goldfish PYY(1-36) to PYY(3-36) in vitro. It also confirms a previously held hypothesis that DPP4 is unable to cleave fish PYY(1-36) that contains N-terminal proline-proline residues. PYY(3-36) had no effects on food intake of goldfish. The appetite inhibitory effects of intraperitoneal and intracerebroventricular injections of 10 ng/g body weight gfPYY(1-36) were abolished by coinjections of BIBP3226, a Y1 receptor antagonist. These results are significant because it shows the lack of generation of endogenous PYY(3-36) and its anorectic effects in goldfish.

Effects of postprandial starvation on mRNA expression of endocrine-, amino acid and peptide transporter-, and metabolic enzyme-related genes in zebrafish (Danio rerio)

The goal of this study was to systematically evaluate the molecular activities of endocrine-, amino acid and peptide transporters-, and metabolic enzyme-related genes in 35-day-old mixed-sex zebrafish (Danio rerio) after feeding . Zebrafish with initial body weights ranging from 9 to 11 mg were fasted for 384 h in a controlled indoor environment. Fish were sampled at 0, 3, 6, 12, 24, 48, 96, 192, and 384 h after fed. Overall, the present study results show that the regulatory mechanism that insulin-like growth factor I negative feedback regulated growth hormone is conserved in zebrafish, as it is in mammals, but that regulation of growth hormone receptors is highly intricate. Leptin and cholecystokinin are time-dependent negative feedback signals, and neuropeptide Y may be an important positive neuropeptide for food intake in zebrafish. The amino acid/carnitine transporters B(0,+) (ATB(0,+)) and broad neutral (0) amino acid transporter 1(B(0)AT1) mRNA levels measured in our study suggest that protein may be utilized during 24-96 h of fasting in zebrafish. Glutamine synthetase mRNA levels were downregulated, and glutamate dehydrogenase, alanine aminotransferase, aspartate transaminase, and trypsin mRNA levels were upregulated after longtime fasting in this study. The mRNA expression levels of fatty acid synthetase decreased significantly (P < 0.05), whereas those of lipoprotein lipase rapidly increased after 96 h of fasting. Fasting activated the expression of glucose synthesis genes when fasting for short periods of time; when fasting is prolonged, the mRNA levels of glucose breakdown enzymes and pentose phosphate shunt genes decreased.

Relative distribution of gastrin-, CCK-8-, NPY- and CGRP-immunoreactive cells in the digestive tract of dorado (Salminus brasiliensis)

The endocrine cells (ECs) of the gastrointestinal mucosa form the largest endocrine system in the body, not only in terms of cell numbers but also in terms of the different produced substances. Data describing the association between the relative distributions of the peptide-specific ECs in relation to feeding habits can be useful tools that enable the creation of a general expected pattern of EC distribution. We aimed to investigate the distribution of ECs immunoreactive for the peptides gastrin (GAS), cholecystokinin (CCK-8), neuropeptide Y (NPY), and calcitonin gene-related peptide (CGRP) in different segments of the digestive tract of carnivorous fish dorado (Salminus brasiliensis) by using immunohistochemistry procedures. The distribution of endocrine cells immunoreactive for gastrin (GAS), cholecystokinin (CCK-8), neuropeptide Y (NPY), and calcitonin gene-related peptide (CGRP) in digestive tract of dorado S. brasiliensis was examined by immunohistochemistry. The results describe the association between the distribution of the peptide-specific endocrine cells and feeding habits in different carnivorous fish. The largest number of endocrine cells immunoreactive for GAS, CCK-8, and CGRP were found in the pyloric stomach region and the pyloric caeca. However, NPY-immunoreactive endocrine cells were markedly restricted to the midgut. The distribution pattern of endocrine cells identified in S. brasiliensis is similar to that found in other carnivorous fishes.

Characterization, tissue distribution and regulation of neuropeptideY in Schizothorax prenanti

In this study, the full-length neuropeptide Y (npy) complementary (c)DNA was cloned in ya fish Schizothorax prenanti. npy cDNA was composed of 789 nucleotides with a 288 nucleotide open reading frame encoding a protein of 96 amino acids. The deduced amino acid sequences contained a 28 amino acids signal peptide followed by a 36 amino acids mature neuropeptide Y (NPY). The npy mRNA was expressed mainly in the brain and eye as detected by real-time quantitative polymerase chain reaction RT-PCR (rt-qPCR). The S. prenanti NPY was detectable from blastulation to hatch, suggesting that npy might be involved in the late embryonic development of S. prenanti. An experiment was conducted to determine the expression profile of npy during feeding of a single meal and during long-term fasting. The expression level of npy in fed fish was significantly decreased at 0.5, 1.5, 3 and 9 h post-feeding (hpf) than in fasting fish. Fasting for 14 days induced an increase in npy messenger (m)RNA expression in the brain. Overall, the results suggest that NPY is a conserved peptide that might be involved in the regulation of feeding and other physiological function in S. prenanti.

Neuropeptide Y mRNA and peptide in the night-migratory redheaded bunting brain

This study investigated the distribution of neuropeptide Y (NPY) in the brain of the night-migratory redheaded bunting (Emberiza bruniceps). We first cloned the 275-bp NPY gene in buntings, with ≥95% homology with known sequences from other birds. The deduced peptide sequence contained all conserved 36 amino acids chain of the mature NPY peptide, but lacked 6 amino acids that form the NPY signal peptide. Using digosigenin-labeled riboprobe prepared from the cloned sequence, the brain cells that synthesize NPY were identified by in-situ hybridization. The NPY peptide containing cell bodies and terminals (fibers) were localized by immunocytochemistry. NPY mRNA and peptide were widespread throughout the bunting brain. This included predominant pallial and sub-pallial areas (cortex piriformis, cortex prepiriformis, hyperpallium apicale, hippocampus, globus pallidus) and thalamic and hypothalamic nuclei (organum vasculosum laminae terminalis, nucleus (n.) dorsolateralis anterior thalami, n. rotundus, n. infundibularis) including the median eminence and hind brain (n. pretectalis, n. opticus basalis, n. reticularis pontis caudalis pars gigantocellularis). The important structures with only NPY-immunoreactive fibers included the olfactory bulb, medial and lateral septal areas, medial preoptic nucleus, medial suprachiasmatic nucleus, paraventricular nucleus, ventromedial hypothalamic nucleus, optic tectum, and ventro-lateral geniculate nucleus. These results demonstrate that NPY is possibly involved in the regulation of several physiological functions (e.g. daily timing feeding, and reproduction) in the migratory bunting.

Characterization of sea bass FSHβ 5' flanking region: transcriptional control by 17β-estradiol

The sea bass follicle-stimulating hormone 5' flanking region (sbFSHβ 5' FR) was cloned and characterized in order to study the molecular mechanisms underlying transcriptional regulation of the sbFSHβ gene. Analysis of the ~3.5 kb of this region revealed the presence of several putative cis-acting elements, including steroid hormone response elements, cAMP response elements, pituitary-specific transcription factor response elements, activator protein-1 response elements and TATA sequence. Deleted constructs containing ~3.5 kb of the sbFSHβ 5' FR fused to a luciferase reporter gene were transiently transfected into human embryonic kidney (HEK 293) and mouse mature gonadotrope (LβT2) cell lines. The sbFSHβ 5' FR was efficiently expressed under basal conditions in LβT2 but not in HEK 293, pointing to both positive and negative regulatory elements. In order to elucidate the estrogen-mediated sbFSHβ transcriptional activity, in vitro treatments with 17β-estradiol were carried out on primary cultures of pituitary cells and LβT2 cells transiently expressing luciferase under the control of sbFSHβ 5' FR. Overall, these results demonstrate that 17β-estradiol inhibits sbFSHβ gene expression directly at the level of the pituitary. However, it was also shown that estrogen did not induce changes of the sbFSH promoter-directed luciferase activity, suggesting that sbFSHβ 5'FR (~3.5 kb) activity is cell type dependent and its estrogen regulation could require cis-acting elements located upstream of the promoter region, which is characterized in this article.

Characterization of neuropeptide Y in snakeskin gourami and the change in its expression due to feeding status and melanocortin 4 receptor expression

In this study, we characterized the neuropeptide Y (NPY) mRNA in snakeskin gourami (Trichogaster pectoralis) (TpNPY). TpNPY displayed characteristics typical of previously reported NPYs, and it exhibited a high degree of homology with the NPY proteins of other vertebrates. A phylogenetic analysis demonstrated that TpNPY was closely related to the NPYs found in the acanthomorpha and salmoniformes fish species. TpNPY was found to be ubiquitously expressed in all brain regions when assessed by real-time RT-PCR and in situ hybridization. In addition, a graded expression level of TpNPY was observed in peripheral tissues; for example, a moderate level of TpNPY was found in the gills, liver, kidney, stomach, intestine, spleen and gonads, while a low level of TpNPY was found in the muscle. The change in expression of TpNPY with respect to daily feeding habits was investigated in distinct brain regions, including the telencephalon, mesencephalon, metencephalon, and diencephalon. Fluctuations in the expression level of TpNPY were observed for a 24h post-prandial period. Except for the telencephalon, a reduction in TpNPY expression was found after a meal, while a peak level of TpNPY was observed 1h before the scheduled breakfast. Furthermore, there was a positive correlation between TpNPY and TpMC4R in the telencephalon and diencephalon throughout the circadian feeding cycle, which suggests that there is a connection between the function of NPY and the melanocortin system for the regulation of daily feeding. Fish brains were incubated with an MC4R antagonist (i.e., HS024), and the expression of TpNPY and TpMC4R was measured. Interestingly, there was a significant relationship between the expression of TpNPY and TpMC4R under the effects of HS024, which demonstrates that there are interactions between MC4R and NPY, particularly in a hyperphagic state.

Neuroendocrine system of the digestive tract in Rhamdia quelen juvenile: an immunohistochemical study

In this work, an immunohistochemical study was performed to determine the distribution and relative frequencies of some neuromodulators of the digestive tract of silver catfish (Rhamdia quelen). The digestive tract of silver catfish was divided into six portions; the oesophagus, stomach, intestine (ascendant, descendant and convoluted segments), and rectum. Immunohistochemical method using a pool of specific antisera against-gastrin, -cholecystokinin-8, -leu-enkephalin, -neuropeptide Y, -calcitonin gene-related peptide (CGRP), and -vasoactive intestinal peptide (VIP) was employed. Immunoreactivity to all antisera was identified in neuroendocrine cells (NECs) localized in the gut epithelium, although no reaction was observed in the oesophagus or stomach. The morphology of NECs immunopositive to each antibody was similar. They were slender in shape, with basally located nucleus, and their main axis perpendicular to the basement membrane. The number of NECs immunoreactive to all antisera was higher in the ascendant and descendant intestine, exhibiting a decreasing trend toward distal segments of the gut. In addition, immunoreactivity to CGRP and VIP was observed in the myenteric plexus and nerve fibers distributed in the mucosal, submucosal and muscular layers. The higher number of immunopositive NECs in the ascendant and descendant intestine may indicate the primary role of these segments in the control of food intake by means of orexigenic and anorexigenic peripheral signals.

An immunohistochemical study of the gut neuroendocrine system in juvenile pejerrey Odontesthes bonariensis (Valenciennes)

In this study, several neuropeptides were identified by immunohistochemistry in neuroendocrine cells (NEC) located in the gut epithelium and nerve cell bodies of the enteric nervous system of pejerrey Odontesthes bonariensis, a species that is a promising candidate for intensive aquaculture. The neuropeptides involved in orexigenic or anorexigenic action, i.e. gastrin, cholecystokinin-8, neuropeptide Y and calcitonin gene-related peptide (CGRP), displayed a significantly higher number of immunoreactive NECs in the anterior intestine, suggesting that this region of the gut plays an important role in the peripheral control of food intake. On the other hand, leu-enkephalin and vasoactive intestinal peptide (VIP), both associated with the modulation of the enteric immune system, showed no significant variations in the mean value of immunopositive NECs between the anterior and posterior intestine. This may indicate that their activity is required at a similar level along the entire gut. In addition, CGRP and VIP-immunoreactive neurons and nerve fibres were observed in the myenteric plexus, which might exert synergistic effects with the neuropeptides immunolocalized in NECs.

Molecular characterization, appetite regulatory effects and feeding related changes of peptide YY in goldfish

Peptide YY (PYY) is a 36 amino acid multifunctional gut-brain hormone in mammals. PYY has recently raised great interest as it was shown to reduce food intake and body weight of mammals. While PYY and its receptors have been sequenced from many non-mammalian vertebrates, its functional role, especially in the regulation of food intake in lower vertebrates remain unknown. In this study, we identified the gene organization of goldfish PYY (gfPYY) and found abundant expression of PYY mRNA in the brain and digestive tract of goldfish. A 2.5-fold increase at 3h post-feeding and a 1.5-fold decrease in fasted animals was observed of PYY mRNA expression in the brain, suggesting an anorectic role for PYY in goldfish. A single intraperitoneal injection of 10 ng/g body weight gfPYY(1-36) or an intracerebroventricular injection of 5 ng/g body weight gfPYY(1-36) caused a 27% or 30% reduction in food intake in goldfish, respectively. Overall, our results, for the first time provide molecular and functional evidence for anorectic actions of PYY in goldfish.

Major genomic events and their consequences for vertebrate evolution and endocrinology

Comparative studies of proteins often face the problem of distinguishing a true orthologue (species homologue) from a paralogue (a gene duplicate). This identification task is particularly challenging for endocrine peptides and neuropeptides because they are short and usually have several invariant positions. For some peptide families, this has led to a terminology with peptide names relating to the first species where a specific peptide sequence was determined, such as chicken or salmon gonadotropin-releasing hormone, or names that highlight amino acid differences, e.g., Lys-vasopressin. With accumulating information from multiple species, such a terminology becomes almost impenetrable for nonexperts and difficult even for aficionados. The sequenced genomes offer a new way to distinguish orthologues and paralogues, namely by location of the genes relative to neighboring genes on the chromosomes. In addition, the genome databases can ideally provide a complete listing of the family members in each species. Many vertebrate gene families have expanded in the two basal tetraploidizations (2R) and the teleost fish third tetraploidization (3R), after which some vertebrate lineages have lost some of the duplicates. We review here some peptide families (neuropeptide Y, oxytocin-vasopressin, and somatostatin) where genomic information helps simplify nomenclature. This approach is useful also for other gene families, such as peptide receptors.

Neuropeptide Y (NPY), cocaine- and amphetamine-regulated transcript (CART) and cholecystokinin (CCK) in winter skate (Raja ocellata): cDNA cloning, tissue distribution and mRNA expression responses to fasting

cDNAs encoding for neuropeptide Y (NPY), cocaine- and amphetamine-regulated transcript (CART) and cholecystokinin (CCK) were cloned in an elasmobranch fish, the winter skate. mRNA tissue distribution was examined for the three peptides as well as the effects of two weeks of fasting on their expression. Skate NPY, CART and CCK sequences display similarities with sequences for teleost fish but in general the degree of identity is relatively low (50%). All three peptides are present in brain and in several peripheral tissues, including gut and gonads. Within the brain, the three peptides are expressed in the hypothalamus, telencephalon, optic tectum and cerebellum. Two weeks of fasting induced an increase in telencephalon NPY and an increase in CCK in the gut but had no effects on hypothalamic NPY, CART and CCK, or on telencephalon CART. Our results provide basis for further investigation into the regulation of feeding in winter skate.

Feeding behavior of fish and its control

Feeding behavior is a complex behavior that is closely associated with food intake. Fish have a wide variety of feeding habits and feeding patterns making them good experimental models for the study of the regulation of feeding behavior. The aquatic nature of fish often creates challenges in the study of feeding behavior and different approaches have been used by researchers, including field studies, observations of free-living animals, and laboratory experiments. Feeding behavior is regulated by a number of environmental factors and also by complex homeostatic mechanisms that involve central and peripheral hormonal factors as well as metabolites. This review summarizes our current knowledge on the control of feeding behavior of fish, with emphasis on the methodology used and on the endocrine and metabolic regulation of feeding.

Evolution of the neuropeptide Y family: new genes by chromosome duplications in early vertebrates and in teleost fishes

Despite sequence information from many vertebrates the evolution of the neuropeptide Y (NPY) family of peptides has been difficult to resolve, particularly among ray-finned fishes. We have used chromosomal location and sequence analyses to identify orthologs and gene duplicates in teleost fish genomes. Our analyses support origin of NPY and peptide YY (PYY) from a common ancestor in early vertebrate evolution through a chromosome duplication. We report here that the teleost tetraploidization generated duplicates of both NPY and PYY and that all four genes are still present in the two sequenced pufferfish genomes Tetraodon nigroviridis and Takifugu rubripes as well as three-spined stickleback, Gasterosteus aculeatus. The zebrafish Danio rerio NPYb gene has probably been lost whereas medaka, Oryzias latipes seems to lack PYYb. Some of the previously published PYY sequences were misidentified and actually constitute NPYb. Our analyses confirm that the peptide previously named PY in some fish species is a duplicate of the PYY gene and hence should be called PYYb. The NPYa and NPYb genes in Takifugu rubripes are predominantly expressed in brain, as detected by RT-PCR, whereas PYYa and PYYb are expressed in several organs including brain, intestine and gonads. Thus, also the resemblance in expression pattern supports the fish gene duplication scenario. Our study shows that when sequence comparisons give ambiguous results, chromosomal location can serve as a useful criterion to identify orthologs. This strategy may help to resolve relationships in several families of short peptides.

Molecular characterization of neuropeptide Y gene in Chinese perch, an acanthomorph fish

The full-length neuropeptide Y (NPY) cDNA of Chinese perch Siniperca chuatsi was 704 bp in length, and contained a 300 bp open reading frame encoding a prepro-NPY with 99 amino acids. The predicted prepro-NPY peptide contained a putative signal peptide of 28 amino acids and a mature NPY of 36 amino acids, followed by the proteolytic processing site Gly-Lys-Arg and 35 amino acids that comprise the C-terminal peptide of NPY. Amino acid alignment and phylogenetic analysis indicate that the predicted Chinese perch prepro-NPY (composed of 99 amino acids) had high identities to the prepro-NPY of acanthomorph fishes (93-95%), whereas it had much lower identities to the prepro-NPY (composed of 96 or 97 amino acids) of cyprinid fishes (59-60%) or mammals (57-63%). Chinese perch NPY gene consists of four exons and three introns. The ratio of intron 2 to intron 3 was over 14 in Chinese perch NPY gene, whereas this ratio was below 4 in zebrafish and mammalian NPY gene. The total size of the Chinese perch NPY gene was 2223 bp, which was only about 28% of the size of NPY gene in higher vertebrate. Analysis of a 1622 bp promoter region of Chinese perch NPY gene, revealed a typical TATA box, a GC box and an untypical CAAT box, located at 84 bp, 101 bp and 303 bp upstream of the start codon respectively. Three STAT binding site-like elements (TCCAGTA) which were necessary for the leptin-induced transcriptional control of rat NPY gene were identified. In consistence to the effect of cortisol on fish brain NPY mRNA expression, four glucocorticoid-responsive elements were detected. Besides the highest expression in brain, substantial level of Chinese perch NPY mRNA expression was detected in the spleen and liver, and trace level of NPY mRNA expression was also detected in the adipose tissue, intestine and muscle. These results indicated that Chinese perch NPY might be involved in the food intake control by leptin and cortisol system, and diversification of NPY signaling should exist between acanthomorph fishes and cyprinid fishes as well as mammals.

Cloning and characterization of neuropeptide Y (NPY) and cocaine and amphetamine regulated transcript (CART) in Atlantic cod (Gadus morhua)

Neuropeptide Y (NPY) and cocaine and amphetamine regulated transcript (CART) are two neuropeptides involved in the regulation of feeding in both mammals and fish. NPY stimulates feeding whereas CART inhibits feeding. In this study, we have cloned the full-length cDNA and complete genomic DNA sequences for NPY and CART in Atlantic cod. Atlantic cod preproNPY share a 45-85% identity with preproNPY from other fish whereas preproCART shows a 70% identity to CART peptides from zebrafish and goldfish. RT-PCR revealed that NPY mRNA is expressed in brain, in particular the forebrain, and in peripheral tissues, including intestine and kidney. CART mRNA is expressed throughout the brain and in ovaries. In order to assess the role of these peptides in the regulation of feeding, we examined changes in mRNA expression in the forebrain before, during and after a meal. NPY and CART mRNA both undergo peri-prandial changes in expression, with NPY levels being elevated around meal time and CART showing a decline 2 h after a meal. Food deprivation for 7 days induced a decrease in CART mRNA expression in the brain but did not affect NPY mRNA expression. Overall, our results suggest that NPY and CART are conserved peptides that might be involved in the regulation of feeding and other physiological functions in Atlantic cod.

Changes in cholecystokinin and peptide Y gene expression with feeding in yellowtail (Seriola quinqueradiata): relation to pancreatic exocrine regulation

In fish, the regulation of digestive enzyme secretion by hormonal control such as cholecystokinin (CCK) and neuropeptide Y (NPY)-related peptide is not well understood. To investigate the roles of fish CCK and peptide Y (PY) in digestive enzyme secretion, mRNA levels of CCK and PY, pyloric caeca enzyme activities and mRNA levels of pancreatic digestive enzymes (lipase, trypsin and amylase) were measured at pre- and post-prandial stages in yellowtail. Pyloric caeca were sampled at 0, 0.5, 1.5, 3, 6, 12, 24 and 48 h after feeding. The mRNA levels of trypsin and amylase increased after feeding, suggesting that transcription was induced by feed ingestion. Digestive enzyme activities decreased in exocrine pancreas after feeding, suggesting the stored enzyme was secreted from pancreas post-prandially. mRNA levels for CCK displayed a time-dependent increase, peaking between 1.5 and 3 h after-feeding followed by a rapid decrease 3 to 6 h after feeding. The mRNA expression pattern of PY was inverse to the pattern of CCK, decreasing until 1.5 h after feeding and then rising to initial levels by 12 h after feeding. These results suggest that CCK and PY work antagonistically in the exocrine pancreas of yellowtail.

Immunohistochemical study on distribution of endocrine cells in gastrointestinal tract of flower fish (Pseudophoxinus antalyae)

AIM: To detect distribution and relative frequency of endocrine cells in gastrointestinal tract of flower fish (Pseudophoxinus antalyae).

METHODS: The intestinal tract of flower fish was divided into four portions from proximal to distal; the enlarged area after oesophagus and anterior, middle and posterior intestine. Immunohistochemical method using the peroxidase anti-peroxidase complex was employed. All antisera between four portions of flower fish were compared using ANOVA.

RESULTS: Eleven types of gut endocrine cells were determined; they were immunoreactive for calcitonin gene related peptide, substance P, vasoactive intestinal peptide, bombesin, somatostatin-14, secretin, TrkA, TrkB, TrkC, neurotensin, neuropeptide Y, which were found in almost all portions of the gastrointestinal tract.

CONCLUSION: The regional distribution and relative frequency of immunoreactive cells in the flower fish, Pseudophoxinus antalyae, are essentially similar to those of other fish.

Gastroenteropancreatic hormones and metabolism in fish

Metabolism of vertebrates integrates a vast array of systems and processes, including the pursuit and capture of food, feeding and digestion of ingested food, absorption and transport of nutrients, assimilation, partitioning and utilization of energy, and the processing and elimination of wastes. Fish, which are the most diverse group of vertebrates and occupy a wide range of habitats and display numerous life history patterns, have proven to be important models for the study of the structure, biosynthesis, evolution, and function of gastroenteropancreatic (GEP) hormones. Food intake is promoted by galanin, neuropeptide Y, and pancreatic polypeptide (PP), while cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1) inhibit food intake. Digestion of ingested food is facilitated by CCK, PP, and secretin by coordinating gastrointestinal tract motility and regulation of exocrine secretion. Somatostatins (SS), on the other hand, generally inhibit exocrine secretions. Insulin facilitates assimilation by promoting the uptake of nutrient molecules (e.g., glucose, amino acids, and fatty acids) into cells. Insulin also is generally anabolic and stimulates the synthesis and deposition of energy reserves (e.g., glycogen, triacylglycerol) as well as of proteins, thereby facilitating organismal growth. Insulin-like growth factors (e.g., IGF-1) also promote cell proliferation and organismal growth. Breakdown and mobilization of stored energy reserves is stimulated by glucagon, GLP-1, and SS. Somatostatins also affect metabolism and reproduction via their effects on the thyroid axis as well as growth via effects on growth hormone (GH) release and perhaps directly via modulation of GH sensitivity. Studies in fish have revealed that GEP hormones play an important role in coordinating the various aspects of metabolism with each other and with the physiological and developmental status of the animal as well as with the environment.

Cholecystokinin and peptide Y in yellowtail (Seriola quinqueradiata): molecular cloning, real-time quantitative RT-PCR, and response to feeding and fasting

In fish, the peptide hormones cholecystokinin (CCK) and peptide Y (PY) may be involved in pancreatic exocrine secretion, as found with mammalian CCK and peptide YY (PYY); CCK stimulates, whereas PYY inhibits, pancreatic exocrine secretion in mammals. However, there is very little information on these hormones in fish; in particular, the function of PY is still unknown. Therefore, as a first step for understanding the role of CCK and PY in regulating pancreatic exocrine in fish, the cDNAs of CCK and PY were cloned from the digestive tract of yellowtail (Seriola quinqueradiata). The peptide sequence of yellowtail CCK-8, DYLGWMDF, is identical to sequences found in several teleosts. The mature form of yellowtail PY consists of 36 amino acids and has high identity to other fish PYs (88.9-97.2%). Real-time quantitative RT-PCR assays were developed to measure yellowtail CCK and PY mRNA levels. CCK mRNA levels were extremely high in the brain and, among the digestive organs, high concentrations were found in the pyloric caeca and anterior intestine. PY mRNA levels were low in the brain and highest in the anterior intestine. In fasting experiments, mRNA levels of CCK and PY in the anterior intestine showed an antagonistic change after fasting; CCK decreased whereas PY increased. These data suggest that CCK and PY in yellowtail may relate to digestion including, enzyme secretion.

cDNA cloning and mRNA expression of neuropeptide Y in orange spotted grouper, Epinephelus coioides

A full-length cDNA encoding the neuropeptide Y (NPY) was cloned from the hypothalamus of orange spotted grouper (Epinephelus coioides) by rapid amplification of cDNA ends approaches. The NPY cDNA sequence is 688 bp long and has an open reading frame of 300 bp encoding prepro-NPY with 99 amino acids. The deduced amino acid sequences contain a 28-amino-acids signal peptide followed by a 36-amino-acids mature NPY peptide. mRNA expression of NPY was determined using semi-quantitative RT-PCR followed by Southern blot analysis. NPY mRNA was expressed in olfactory bulb, telencephalon, pituitary, hypothalamus, optic tectum-thalamus, medulla oblongata, cerebellum and spinal cord. Low levels of NPY mRNA expression were found in retina, ovary and stomach, while much lower levels of expression were detected in liver, heart, gill, skin, anterior intestine, thymus and blood. No NPY mRNA expression was observed in unfertilized eggs, newly fertilized eggs, 16-cells stage and morula stage of the embryo and lower levels of expression were detected in the blastula, gastrula and neurula stages. It was highly expressed from lens formation stage to 52-day-old larval stage. NPY might be involved in the late embryonic and larval development of the orange spotted grouper.

Neuropeptides and the control of food intake in fish

The brain, particularly the hypothalamus, integrates input from factors that stimulate (orexigenic) and inhibit (anorexigenic) food intake. In fish, the identification of appetite regulators has been achieved by the use of both peptide injections followed by measurements of food intake, and by molecular cloning combined with gene expression studies. Neuropeptide Y (NPY) is the most potent orexigenic factor in fish. Other orexigenic peptides, orexin A and B and galanin, have been found to interact with NPY in the control of food intake in an interdependent and coordinated manner. On the other hand cholecystokinin (CCK), cocaine and amphetamine-regulated transcript (CART), and corticotropin-releasing factor (CRF) are potent anorexigenic factors in fish, the latter being involved in stress-related anorexia. CCK and CART have synergistic effects on food intake and modulate the actions of NPY and orexins. Although leptin has not yet been identified in fish, administration of mammalian leptin inhibits food intake in goldfish. Moreover, leptin induces CCK gene expression in the hypothalamus and its actions are mediated at least in part by CCK. Other orexigenic factors have been identified in teleost fish, including the agouti-related protein (AgRP) and ghrelin. Additional anorexigenic factors include bombesin (or gastrin-releasing peptide), alpha-melanocyte-stimulating hormone (alpha-MSH), tachykinins, and urotensin I. In goldfish, nutritional status can modify the expression of mRNAs encoding a number of these peptides, which provides further evidence for their roles as appetite regulators: (1) brain mRNA expression of CCK, CART, tachykinins, galanin, ghrelin, and NPY undergo peri-prandial variations; and (2) fasting increases the brain mRNA expression of NPY, AgRP, and ghrelin as well as serum ghrelin levels, and decreases the brain mRNA expression of tachykinins, CART, and CCK. This review will provide an overview of recent findings in this field.

The evolution of neuroendocrine peptides

The genomes of extant vertebrates have been shaped by a series of whole genome and individual gene duplication events. The 2R hypothesis, which postulates that two whole genome duplications occurred in relatively rapid succession very early in chordate evolution, is gaining increasing acceptance. A further entire genome duplication is believed to have occurred in the ancestral fish lineage approximately 320-350 Myr ago, as well as more recent independent tetraploidization events, mostly but not exclusively, in particular teleost and amphibian lineages. Superimposed upon these whole genome duplications are tandem or segmental duplications of individual genes or groups of genes that have taken place at different rates in the various vertebrate lineages. The majority of duplicated genes become pseudogenes or are deleted but some may evolve to encode components with new functional roles. Genes encoding members of neuropeptide Y- and tachykinin-families are associated with the HOX-bearing chromosomes and these systems provide examples of duplication events that have led to rapid evolution of the duplicated gene which has occasionally produced peptides, such as pancreatic polypeptide, seminalplasmin and hemokinin-1, with new biological functions.

PREDICT modeling and in-silico screening for G-protein coupled receptors

G-protein coupled receptors (GPCRs) are a major group of drug targets for which only one x-ray structure is known (the nondrugable rhodopsin), limiting the application of structure-based drug discovery to GPCRs. In this paper we present the details of PREDICT, a new algorithmic approach for modeling the 3D structure of GPCRs without relying on homology to rhodopsin. PREDICT, which focuses on the transmembrane domain of GPCRs, starts from the primary sequence of the receptor, simultaneously optimizing multiple 'decoy' conformations of the protein in order to find its most stable structure, culminating in a virtual receptor-ligand complex. In this paper we present a comprehensive analysis of three PREDICT models for the dopamine D2, neurokinin NK1, and neuropeptide Y Y1 receptors. A shorter discussion of the CCR3 receptor model is also included. All models were found to be in good agreement with a large body of experimental data. The quality of the PREDICT models, at least for drug discovery purposes, was evaluated by their successful utilization in in-silico screening. Virtual screening using all three PREDICT models yielded enrichment factors 9-fold to 44-fold better than random screening. Namely, the PREDICT models can be used to identify active small-molecule ligands embedded in large compound libraries with an efficiency comparable to that obtained using crystal structures for non-GPCR targets.

Long-term exposure to continuous light inhibits precocity in European male sea bass (Dicentrarchus labrax, L.): hormonal aspects

The effect of long-term exposure to continuous light on the hormonal aspects of the reproductive axis was investigated in juvenile male sea bass (Dicentrarchus labrax, L.) during the first annual cycle. Four-month-old fish were exposed to a simulated natural photoperiod (NP) and a continuous light (24 h) regime (LL) under natural conditions of temperature (13.3-25.8 degrees C). A dot-blot technique was used to analyse gonadotropin (the common glycoprotein alpha, GPalpha; the follicle stimulating hormone beta, FSHbeta; and the luteinizing hormone beta, LHbeta, subunits) mRNA levels in the pituitary during the experiment. A homologous ELISA was used to determine pituitary sea bream gonadotropin-releasing hormone (sbGnRH) and LH and plasma LH levels; gonadal and plasma sex steroids concentrations were determined by specific immunoassays. LL significantly inhibited the expression of all three gonadotropins subunits in the pituitary. However, no significant differences on plasma LH levels were observed between NP and LL groups throughout the period of the experience. Long-term exposure to LL regime was extremely effective in inhibiting gonadal growth and hence precocious maturation as well as the accumulation of Testosterone (T) and 11-ketotestosterone (11-KT) in the gonads compared to the control group. 11-KT plasma levels remained low and unchanged in the LL group during the study. This work describe important alterations of the endocrine system, particularly at the pituitary-gonad axis provoked by exposure to continuous illumination and discusses the mechanism by which precocity in male sea bass is generated.

Endogenous melanocortin antagonist in fish: structure, brain mapping, and regulation by fasting of the goldfish agouti-related protein gene

Agouti-related protein (AGRP) is a naturally occurring antagonist of melanocortin. In mammals, central AGRP expression is restricted to the arcuate nucleus in which it plays a key role in the control of energy balance by antagonizing melanocortin effects at melanocortin 4 receptors. In goldfish, melanocortin 4 receptor is profusely expressed within the main brain areas for the control of energy balance, and central administration of agonist or antagonist analogs inhibits or stimulates food intake, respectively. Here we demonstrate that the goldfish genome has a homologous gene to mammalian AGRP. Detailed brain mapping by in situ hybridization shows that AGRP is exclusively expressed in the ventrobasal hypothalamic lateral tuberal nucleus, the teleostean homolog of the arcuate nucleus. Fasting up-regulates its mRNA levels in the lateral tuberal nucleus. In the periphery, AGRP is expressed in several tissues including ovary, muscle, and ventral skin, suggesting that AGRP might regulate peripheral actions of melanocortin peptides. The results provide the first evidence for an endogenous melanocortin antagonist in nontetrapod species and suggest that hypothalamic overexpression during fasting might regulate the inhibitory effects of melanocortin peptides on food intake in goldfish.

Molecular characterization of sea bass gonadotropin subunits (alpha, FSHbeta, and LHbeta) and their expression during the reproductive cycle

Reproduction is controlled by two pituitary gonadotropin hormones, follicle-stimulating hormone (FSH) and luteinizing hormone (LH). This study reports the cloning, sequence analysis, and gene expression of gonadotropin (GTH) subunits from the European sea bass (Dicentrarchus labrax). The GTH subunits were cloned from a sea bass brain-pituitary cDNA library. The nucleotide sequences of the common alpha, the FSHbeta, and the LHbeta subunit cDNAs were 625, 521, and 591 base pair (bp) long, respectively, encoding for mature peptides of 94, 105, and 115 amino acids (aa), respectively. Sequence analysis showed that sea bass FSHbeta is more similar to higher vertebrate FSHbeta's (35-37%) than to LHbeta's (26-30%), whereas sea bass LHbeta is more similar to LHbeta's (40-53%) than to FSHbeta's (26-41%). Phylogenetic analysis of fish GTH sequences grouped the beta subunits into two groups, FSH and LH, distributed into four classes, corresponding to the accepted divisions of Elopomorphs, Ostariophysis, Salmonids, and Percomorphs. A dot-blot technique was developed to analyze GTH pituitary mRNA levels during the reproductive cycle of male sea bass. From October (initiation of gametogenesis) to February (spermiation), the expression of all three subunits in the pituitary increased in parallel, concomitantly with the gonadosomatic index (GSI) and the accumulation of LH protein in the pituitary, all values declining sharply at post-spermiation. This study demonstrates that the pituitary of sea bass contains two gonadotropin hormones and that both gonadotropins are probably involved in the control of gametogenesis, gamete maturation, and spermiation.

Cloning, pharmacology, and distribution of the neuropeptide Y-receptor Yb in rainbow trout

This work describes the isolation and pharmacological characterization of a neuropeptide Y (NPY) receptor from rainbow trout (Oncorhynchus mykiss). The receptor exhibits approximately 45% amino acid sequence identity to mammalian Y1-subfamily receptors, Y1, Y4 and y6, a similar degree of identity as these subtypes display to one another. Because it displays highest sequence identity to zebrafish Yb (75%), we named it the trout Yb receptor. The receptor exhibits high binding affinity for zebrafish and human NPY and peptide YY (PYY) but not truncated forms of the peptides. Human pancreatic polypeptide (PP) also binds with high affinity. Y1 selective antagonists exhibit poor binding as is the case for Y2 and Y5 selective ligands. This binding profile supports membership in the Y1 subfamily. Sequence data also support this relationship suggesting that Yb is a fourth and separate member of the Y1 subfamily. NPY has a number of important physiological functions such as regulating food intake and reproduction. The expression of the receptor in the hypothalamus and telencephalon suggests a possible role in these processes. This and other receptors from this species have potential for improving aquaculture.