Conservation of Three-Dimensional Helix-Loop-Helix Structure through the Vertebrate Lineage Reopens the Cold Case of Gonadotropin-Releasing Hormone-Associated Peptide

GnRH-associated peptide (GAP) is the C-terminal portion of the gonadotropin-releasing hormone (GnRH) preprohormone. Although it was reported in mammals that GAP may act as a prolactin-inhibiting factor and can be co-secreted with GnRH into the hypophyseal portal blood, GAP has been practically out of the research circuit for about 20 years. Comparative studies highlighted the low conservation of GAP primary amino acid sequences among vertebrates, contributing to consider that this peptide only participates in the folding or carrying process of GnRH. Considering that the three-dimensional (3D) structure of a protein may define its function, the aim of this study was to evaluate if GAP sequences and 3D structures are conserved in the vertebrate lineage. GAP sequences from various vertebrates were retrieved from databases. Analysis of primary amino acid sequence identity and similarity, molecular phylogeny, and prediction of 3D structures were performed. Amino acid sequence comparison and phylogeny analyses confirmed the large variation of GAP sequences throughout vertebrate radiation. In contrast, prediction of the 3D structure revealed a striking conservation of the 3D structure of GAP1 (GAP associated with the hypophysiotropic type 1 GnRH), despite low amino acid sequence conservation. This GAP1 peptide presented a typical helix-loop-helix (HLH) structure in all the vertebrate species analyzed. This HLH structure could also be predicted for GAP2 in some but not all vertebrate species and in none of the GAP3 analyzed. These results allowed us to infer that selective pressures have maintained GAP1 HLH structure throughout the vertebrate lineage. The conservation of the HLH motif, known to confer biological activity to various proteins, suggests that GAP1 peptides may exert some hypophysiotropic biological functions across vertebrate radiation

Conservation of Three-Dimensional Helix-Loop-Helix Structure through the Vertebrate Lineage Reopens the Cold Case of Gonadotropin-Releasing Hormone-Associated Peptide

International audienceGnRH-associated peptide (GAP) is the C-terminal portion of the gonadotropin-releasing hormone (GnRH) preprohormone. Although it was reported in mammals that GAP may act as a prolactin-inhibiting factor and can be co-secreted with GnRH into the hypophyseal portal blood, GAP has been practically out of the research circuit for about 20 years. Comparative studies highlighted the low conservation of GAP primary amino acid sequences among vertebrates, contributing to consider that this peptide only participates in the folding or carrying process of GnRH. Considering that the three-dimensional (3D) structure of a protein may define its function, the aim of this study was to evaluate if GAP sequences and 3D structures are conserved in the vertebrate lineage. GAP sequences from various vertebrates were retrieved from databases. Analysis of primary amino acid sequence identity and similarity, molecular phylogeny, and prediction of 3D structures were performed. Amino acid sequence comparison and phylogeny analyses confirmed the large variation of GAP sequences throughout vertebrate radiation. In contrast, prediction of the 3D structure revealed a striking conservation of the 3D structure of GAP1 (GAP associated with the hypophysiotropic type 1 GnRH), despite low amino acid sequence conservation. This GAP1 peptide presented a typical helix-loop-helix (HLH) structure in all the vertebrate species analyzed. This HLH structure could also be predicted for GAP2 in some but not all vertebrate species and in none of the GAP3 analyzed. These results allowed us to infer that selective pressures have maintained GAP1 HLH structure throughout the vertebrate lineage. The conservation of the HLH motif, known to confer biological activity to various proteins, suggests that GAP1 pep-tides may exert some hypophysiotropic biological functions across vertebrate radiation

Fish skin pigmentation in aquaculture: the influence of rearing conditions and its neuroendocrine regulation

Skin pigmentation pattern is a species-specific characteristic that depends on the number and the spatial combination of several types of chromatophores. This feature can change during life, for example in the metamorphosis or reproductive cycle, or as a response to biotic and/or abiotic environmental cues (nutrition, UV incidence, surrounding luminosity, and social interactions). Fish skin pigmentation is one of the most important quality criteria dictating the market value of both aquaculture and ornamental species because it serves as an external signal to infer its welfare and the culture conditions used. For that reason, several studies have been conducted aiming to understand the mechanisms underlying fish pigmentation as well as the influence exerted by rearing conditions. In this context, the present review focuses on the current knowledge on endocrine regulation of fish pigmentation as well as on the aquaculture conditions affecting skin coloration. Available information on Iberoamerican fish species cultured is presented

Digestive enzyme activities during pejerrey (Odontesthes bonariensis) ontogeny

The first step for assessing and refining the nutritional requirements during the larval and early juvenile stages of a fish is the study of the ontogeny of digestive system functionality. The combination of these studies with ecological and anatomical knowledge of the species of interest establishes the base for facing one of the major aquaculture challenges: promoting larvae growth and survival. Considering this, changes in the activity of the main digestive (pancreatic and intestinal) enzymes during larval development of the agastric South America pejerrey (Odontesthes bonariensis) were described in the present work. Digestive enzymes for protein, lipid, and carbohydrate hydrolysis were present from the first-week post-hatching (6.85 ± 0.07 mm total length, TL). Changes in the activity of trypsin, chymotrypsin, and alkaline protease indicated that the exocrine pancreas in pejerrey achieves its functional development at the 2nd week post-hatching (9.22 ± 0.17 mm TL). Interestingly, α-amylase and maltase total activity progressively increased over development, suggesting that gradual incorporation of dietary carbohydrates in a feeding protocol may have a protein-sparing effect, as well as a cheap and fast way to obtain energy for the development and growth of pejerrey. The analysis of intestinal enzymes revealed that the typical shift between intracellular and luminal protein digestion that occurs during larval development in gastric species does not take place in pejerrey, indicating that in agastric species intracellular protein digestion plays a major role in comparison to luminal digestion during larval development. Contrary to gastric species, our results suggest that the ratio of alkaline phosphatase to leucine-aminopeptidase for evaluating gut maturation in agastric species is not recommended, and other parameters should be measured when evaluating the maturation process in fish larvae from this group of species.info:eu-repo/semantics/acceptedVersio

From zero to ossified: Larval skeletal ontogeny of the Neotropical Cichlid fish Cichlasoma dimerus

The identification of skeletal elements, the analysis of their developmental sequence, and the time of their appearance during larval development are essential to broaden the knowledge of each fish species and to recognize skeletal abnormalities that may affect further fish performance. Therefore, this study aimed to provide a general description of the development of the entire skeleton highlighting its variability in Cichlasoma dimerus. Larvae of C. dimersus were stained with alcian blue and alizarin red from hatching to 25 days posthatching. Skeletogenesis began with the endoskeletal disk and some cartilage structures from the caudal fin and the splachnocranium, while the first bony structure observed was the cleithrum. When larvae reached the free-swimming and exogenous feeding stage, mostly bones from the jaws, the branchial arches, and the opercle series evidenced some degree of ossification, suggesting that the ossification sequence of C. dimerus adjusts to physiological demands such as feeding and ventilation. The caudal region was the most variable regarding meristic counts and evidenced higher incidence of bone deformities. In conclusion, this work provides an overview of C. dimerus skeletogenesis and lays the groundwork for further studies on diverse topics, like developmental plasticity, rearing conditions, or phylogenetic relationships.We thank the Laboratory of Entomology and the Laboratory of Amphibian Biology-Animal Histology of the FCEN-UBA for allowing the use of their Leica MZ6 and Leica EZ4D stereoscopic microscopes. Universidad de Buenos Aires (UBACyT 20020190100294BA to P. G. V.), Agencia Nacional de Promoción Científica y Tecnológica (PICT-2018-02577 to P. G. V.). MICIU and the European Social Fund, “The European Social Fund invests in your future” through the Ramón y Cajal (Ref. RYC2018-025337-I to I. F.) contract from the Plan Estatal de Investigación Científica y Técnica e Innovación 2017–2020. 632. This work was carried out with the collaboration of Red CYTED LARVAplus (117RT0521).Peer reviewe