Global map of oxytocin/vasopressin-like neuropeptide signalling in insects.

Oxytocin and vasopressin mediate a range of physiological functions that are important for osmoregulation, reproduction, social behaviour, memory and learning. The origin of this signalling system is thought to date back ~600 million years. Oxytocin/vasopressin-like peptides have been identified in several invertebrate species and they appear to be functionally related across the entire animal kingdom. There is little information available about the biology of this peptide G protein-coupled receptor signalling system in insects. Recently over 200 insect genome/transcriptome datasets were released allowing investigation of the molecular structure and phylogenetic distribution of the insect oxytocin/vasopressin orthologue - inotocin peptides and their receptors. The signalling system is present in early arthropods and representatives of some early-diverging lineages. However, Trichoptera, Lepidoptera, Siphonaptera, Mecoptera and Diptera, lack the presence of inotocin genes, which suggests the peptide-receptor system was probably lost in their common ancestor ~280 million-years-ago. In addition we detected several losses of the inotocin signalling system in Hemiptera (white flies, scale insects and aphids), and the complete absence in spiders (Chelicerata). This unique insight into evolutionarily patterns and sequence diversity of neuroendocrine hormones will provide opportunities to elucidate the physiology of the inotocin signalling system in one of the largest group of animals.

Endogenous vs exogenous oxytocin / Oxitocina endógena vs exógena

No disponible

Molecular evolution of the oxytocin-oxytocin receptor system in eutherians.

Oxytocin (OXT) is a nine-amino-acid peptide hormone that is mainly released at the times of uterine contractions during parturition and milk ejection during lactation, whereas a similar peptide hormone, arginine vasopressin, primarily exerts direct antidiuretic action on the kidney and causes vasoconstriction of the peripheral vessels. The genes coding for these peptides are tandemly located on the same chromosome. A tandem duplication occurring in the common ancestor of jawed vertebrates has been proposed as responsible. In contrast to the two peptide hormones, only one oxytocin receptor (OXTR) but three arginine vasopressin receptors (AVPR1A, AVPR1B, and AVPR2) are known; these receptors probably arose from two rounds of genome duplication in the common ancestor of vertebrates. In this study, we addressed the molecular evolution of the OXT-OXTR system in eutherians. Our analyses suggest that an amino acid change from isoleucine to lysine on the eighth site (I8L) of the peptide, which corresponded to a change from mesotocin to OXT, had occurred during the common ancestral lineage of eutherians. At around the same time that the emergence of OXT occurred, functional constraints on the OXT receptor (pre-OXTR) might have relaxed, and a series of nonsynonymous substitutions might have accumulated. Only a few of these nonsynonymous substitutions might have contributed to reestablishing the molecular relationship between the OXT ligand and its receptor, after which functional constraints on the OXTR were reinstated. Since the OXT-OXTR system plays an important role in eutherians, the evolution of the OXT-OXTR system was probably an essential component of the genesis of the eutherian signature.

Neuropeptide families: evolutionary perspectives.

Examination of neuropeptide families can provide information about phyletic relationships and evolutionary processes. In this article the oxytocin/vasopressin family, growth hormone releasing factor (GRF) superfamily and the substance P/tachykinin family have been considered in detail because they have been isolated from an extraordinarily diverse array of species from several vertebrate classes and invertebrate phyla. More important is that the nucleotide sequence of mRNA or cDNA encoding many of these peptides has been determined, which has allowed evolutionary distances to be estimated based on the DNA mutation rate. The origin of a given family lies in a primordial gene that arose many millions of years ago, and through time, exon duplication and insertion, gene duplication, point mutation and exon loss, the family developed into the forms that are now recognised. For example, in birds, GRF and pituitary adenylate cyclase activating peptide (PACAP) are encoded by the same gene, which probably arose as a result of exon duplication and tandem insertion of the ancestral GRF gene. In mammals GRF is the sole product on one gene, and PACAP is the product of a gene that also produces PACAP-related peptide (PRP), which is homologous to GRF. Thus it appears that between birds and mammals the GRF/PACAP gene duplicated: exon loss gave rise to the mammalian GRF gene, while mutation led to the formation of the mammalian PRP/PACAP gene. The neuropeptide Y superfamily is considered briefly, as is cionin, which is an invertebrate peptide that is closely related to the mammalian gastrin/cholecystokinin family.