Gonadotropin-Releasing Hormone and Adipokinetic Hormone Signaling Systems Share a Common Evolutionary Origin

Gonadotropin-releasing hormone (GnRH) is a critical and central hormone that regulates vertebrate reproduction. The high conservation of GnRH signaling within the chordates (deuterostomians) raises the important question as to whether its appearance might date back prior to the divergence of protostomian and deuterostomian lineages, about 700 million years ago. This leads to several important questions regarding the evolution of the GnRH family. Has GnRH been retained in most protostomian lineages? And was regulation of reproduction already a function of ancestral GnRH? The first question can undoubtedly be answered affirmatively since several GnRH-like sequences have been found in wide variety of protostomian and deuterostomian phyla. However, based on their different primary functions in different phyla – which implies a less unanimous answer on the second question – consistency in the nomenclature of this peptide family has been lost. A comparative and phylogenetic approach shows that the ecdysozoan adipokinetic hormones (AKHs), lophotrochozoan GnRHs and chordate GnRHs are structurally related and suggests that they all originate from a common ancestor. This review supports the view that the AKH–GnRH signaling system probably arose very early in metazoan evolution, prior to the divergence of protostomians and deuterostomians

The functional characterization of the pigment dispersing factor (PDF) pathway in the nematode Caenorhabditis elegans.

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/* Style Definitions */ table.MsoNormalTable {mso-style-name:Standaardtabel; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;}The soildwelling nematode Caenorhabditis elegansis well established as a model for studying the molecular mechanisms underlyingbehavior because it has a fully sequenced genome, is easy to manipulate atgene- and transcript level, is either a self-fertilizing hermaphrodite or amale and because its nervous system has been extensively mapped. In this study, C. elegans was used to uncover the functions of three related neuropeptidesof the pigment dispersing hormone (PDH) family and of their receptors. The first members of the PDH neuropeptidefamily were discovered in crustaceans where they are exclusively called PDHs. The subsequently discovered homologues in insectsand nematodes are called pigment dispersing factors (PDFs). The neuropeptides PDF-1a, PDF-1b (encoded bythe pdf-1 gene) and PDF-2 (encoded bythe pdf-2 gene) and their receptorsPDFR-1a, b and c (isoforms encoded by the pdfr-1gene) are part of the PDF signaling pathway in C. elegans. Whereas PDH incrustaceans and PDF in insects are respectively engaged in pigment dispersionand circadian rhythms, C. elegans doesnot display pigment dispersion and until recently, was believed not to displaycircadian rhythms either. This projectaimed to characterize the PDF signaling pathway in C. elegans by 1) comparing the PDF neuropeptides, precursorproteins and receptors to crustacean PDH proteins and receptors at the level ofamino acid sequence as well as assessing the pigment dispersing ability of the C. elegans peptides in a crustaceanmodel, the shrimp Palaemon pacificus,2) studying behavioral traits of mutants wherein the pdf genes are compromised and 3) studying expression of the pdf genes in a site and time specificmanner.Althoughoverall precursor- and receptor structures are well conserved, it is clear fromthe comparison of amino acid sequences and length of the C. elegans PDF peptides that they deviate considerably from crustaceanPDH peptides. Although, PDF-1a and bboth are able to cause pigment dispersion in the shrimp P. pacificus, PDF-2 is not. This characteristic can be attributed to the N-terminal N-ELIN sequencewhich is generally conserved in crustacean PDH peptides and partially missingin PDF-2. Priorto the start of the present study, it was already known that pdf-1 is involved in the regulation oflocomotion sinceabsence of pdf-1 resultsin a reduction of speed and increase of reversals in crawling animals. In this study, a pdfr-1 mutant was generated and additionally, pdf-2 mutants became available for research. We here demonstrate that apart from pdf-1, also pdf-2 and pdfr-1 areinvolved in the regulation of locomotion as pdfr-1mutants display a similar but stronger crawling phenotype as pdf-1 animals. pdf-2 onthe other hand, is specifically involved in inducing reversals rather thanlocomotion speed. Moreover, PDFsignaling regulates another locomotion gait, namely swimming, as both pdf-1 and pdfr-1 mutants display reduced swimming activity. Although pdf-1expression levels do not vary during the course of the day, there are strongpresumptions that pdf-1 is alsoengaged in the regulation of circadian activity rhythms based on circadianactivity levels. The reintroduction of the different PDFreceptor isoforms in pdfr-1 mutants showsthat PDFR-1a, b and c are all involved in the regulation of locomotion. Transgenic C. elegans expressing fluorescent reporter proteins reveal that pdfr-1 is expressed in both neurons andbody wall muscles, two different tissues that are generally known for theirinvolvement in locomotion. Althoughmuscle specific expression of any of the three receptor isoforms was notsufficient to restore the diminished swimming activity in pdfr-1 mutants, pan-neuronal expression did restore activitylevels, suggesting that locomotion is mainly under neuronal control. Moreover, by studying body wall musclestructure, we show that the overall muscle structure is intact in pdfr-1 mutants. Forthe first time, we provide evidence that PDF signaling regulates reproductiveprocesses in both self-fertilizing hermaphrodites and in males. Although the brood sizes of hermaphroditesremain unchanged in pdf-1, pdf-2 and pdfr-1 mutants, the overall timing of egg-laying in pdf-1, pdf-2 and pdf-1/pdf-2 doublemutantsis delayed. pdfr-1 mutants seem superficially unaffected but in fact retainmore eggs in their uterus compared to wild type worms. A model including stimulation of egg-layingthrough the PDF peptides, PDFR-1a and b and the G-protein G&#945;s, andinhibition of egg-laying through the constitutively active PDFR-1c and G&#945;i/ois proposed based on these results. Alsomales are dependent on proper PDF signaling: matings with pdf-1, pdf-2 and pdfr-1 males show a reduced success rate. Overall,the PDF signaling system in C. elegansis similar to and shares functions with the corresponding systems incrustaceans and insects. In addition,new kinds of behavior such as male mating behavior could be functionally linkedto the PDF pathway. The extensivegenetic toolkit available for C. elegansallows further dissection of these in the future.nrpages: 173status: publishe

Pigment dispersing hormone-like signaling in Caenorhabditis elegans

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Vasopressin/Oxytocin related signaling regulates associative learning in Caenorhabditis elegans

oral presentationstatus: publishe

Pigment-dispersing factor signaling in the circadian system of Caenorhabditis elegans

The neuropeptide pigment-dispersing factor (PDF) is important for the generation and entrainment of circadian rhythms in the fruitfly Drosophila melanogaster. Recently two pdf homologs, pdf-1 and pdf-2, and a PDF receptor, pdfr-1, have been found in Caenorhabditis elegans and have been implicated in locomotor activity. In this work, we have studied the role of the PDF neuropeptide in the circadian system of C. elegans and found that both pdf-1 and pdf-2 mutants affect the normal locomotor activity outputs. In particular, loss of pdf-1 induced circadian arrhythmicity under both light-dark (LD) and constant dark (DD) conditions. These defects can be rescued by a genomic copy of the pdf-1 locus. Our results indicate that PDF-1 is involved in rhythm generation and in the synchronization to LD cycles, as rhythmic patterns of activity rapidly disappear when pdf-1 mutants are recorded under both entrained and free-running conditions. The role of PDF-2 and the PDF receptors is probably more complex and involves the interaction between the two pdf paralogues found in the nematode.status: publishe

Neuroendocrine signalling systems in Caenorhabditis elegans

status: publishe

A pharmacological study of NLP-12 neuropeptide signaling in free-living and parasitic nematodes

status: publishe

A forward mutagenesis approach to study the control of reproduction in C. elegans

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C. elegans homologs of insect clock proteins: a tale of many stories

As a consequence of the Earth's axial rotation, organisms display daily recurring rhythms in behavior and biochemical properties, such as hormone titers. The neuronal system controlling such changes is best studied in the fruit fly Drosophila melanogaster. In the nematode worm Caenorhabditis elegans, most homologs of these genes function in the heterochronic pathway controlling the (timing of) developmental events. Recent data indicate that in the worm at least one of the genes involved in developmental timing is also active in circadian rhythm control, thereby opening up new perspectives on a central (neuronal) timer interfering with many processes. Also, new neuropeptidergic clock homologs have been identified in nematodes, supporting the idea of a broad range of clock-regulated targets. We will describe the current knowledge on homologous clock genes in C. elegans with a focus on the recently discovered pigment dispersing factor gene homologs. Similarities between developmental and daily timing are discussed.status: publishe

Vasopressin/Oxytocin-Related Signaling Regulates Gustatory Associative Learning in C. elegans

Vasopressin- and oxytocin-related neuropeptides are key regulators of animal physiology, including water balance and reproduction. Although these neuropeptides also modulate social behavior and cognition in mammals, the mechanism for influencing behavioral plasticity and the evolutionary origin of these effects are not well understood. Here, we present a functional vasopressin- and oxytocin-like signaling system in the nematode Caenorhabditis elegans. Through activation of its receptor NTR-1, a vasopressin/oxytocin- related neuropeptide, designated nematocin, facilitates the experience-driven modulation of salt chemotaxis, a type of gustatory associative learning in C. elegans. Our study suggests that vasopressin and oxytocin neuropeptides have ancient roles in modulating sensory processing in neural circuits that underlie behavioral plasticity