Origin of Secretin Receptor Precedes the Advent of Tetrapoda: Evidence on the Separated Origins of Secretin and Orexin

At present, secretin and its receptor have only been identified in mammals, and the origin of this ligand-receptor pair in early vertebrates is unclear. In addition, the elusive similarities of secretin and orexin in terms of both structures and functions suggest a common ancestral origin early in the vertebrate lineage. In this article, with the cloning and functional characterization of secretin receptors from lungfish and X. laevis as well as frog (X. laevis and Rana rugulosa) secretins, we provide evidence that the secretin ligand-receptor pair has already diverged and become highly specific by the emergence of tetrapods. The secretin receptor-like sequence cloned from lungfish indicates that the secretin receptor was descended from a VPAC-like receptor prior the advent of sarcopterygians. To clarify the controversial relationship of secretin and orexin, orexin type-2 receptor was cloned from X. laevis. We demonstrated that, in frog, secretin and orexin could activate their mutual receptors, indicating their coordinated complementary role in mediating physiological processes in non-mammalian vertebrates. However, among the peptides in the secretin/glucagon superfamily, secretin was found to be the only peptide that could activate the orexin receptor. We therefore hypothesize that secretin and orexin are of different ancestral origins early in the vertebrate lineage

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Structural and functional divergence of growth hormone-releasing hormone receptors in early sarcopterygians: lungfish and Xenopus.

The evolutionary trajectories of growth hormone-releasing hormone (GHRH) receptor remain enigmatic since the discovery of physiologically functional GHRH-GHRH receptor (GHRHR) in non-mammalian vertebrates in 2007. Interestingly, subsequent studies have described the identification of a GHRHR(2) in chicken in addition to the GHRHR and the closely related paralogous receptor, PACAP-related peptide (PRP) receptor (PRPR). In this article, we provide information, for the first time, on the GHRHR in sarcopterygian fish and amphibians by the cloning and characterization of GHRHRs from lungfish (P. dolloi) and X. laevis. Sequence alignment and phylogenetic analyses demonstrated structural resemblance of lungfish GHRHR to their mammalian orthologs, while the X. laevis GHRHR showed the highest homology to GHRHR(2) in zebrafish and chicken. Functionally, lungfish GHRHR displayed high affinity towards GHRH in triggering intracellular cAMP and calcium accumulation, while X. laevis GHRHR(2) was able to react with both endogenous GHRH and PRP. Tissue distribution analyses showed that both lungfish GHRHR and X. laevis GHRHR(2) had the highest expression in brain, and interestingly, X. laevis(GHRHR2) also had high abundance in the reproductive organs. These findings, together with previous reports, suggest that early in the Sarcopterygii lineage, GHRHR and PRPR have already established diverged and specific affinities towards their cognate ligands. GHRHR(2), which has only been found in xenopus, zebrafish and chicken hitherto, accommodates both GHRH and PRP

Functional characterization of lfGHRHR and xGHRHR₂.

<p>Intracellular cAMP accumulation ([cAMP]_i) in response to 100 nM of GHRH and related peptides on CHO-K1 cells transfected with (A) lfGHRHR and (D) xGHRHR₂ (*** indicates <i>P</i><0.001, ** indicates <i>P</i><0.01, and * indicates <i>P</i><0.05). Effects of GHRH and related peptides on graded concentrations of peptides on [cAMP]_i (B) lfGHRHR- and (E) xGHRHR₂-expressing cells. The intracellular calcium mobilization ([Ca²⁺]_i) assays of (C) lfGHRHR- and (F) xGHRHR₂-expressing cells. For [cAMP]_i, values represent mean ± SEM (n = 4). For ([Ca²⁺]_i, data were expressed in ΔRFU value (maximum changes in the fluorescence signals from baseline) and converted to percentage of the maximum of xGHRH-induced [Ca²⁺]_i elevation. Results are expressed as mean ± SEM from at least 10 independent experiments, cell number = 20 to 50. Peptide species: h, human; x, <i>X. laevis</i>, zf, zebrafish <i>D. rerio</i>; gf, goldfish <i>C. auratus</i>.</p

Evolutionary analysis of the osteichthyans secretin GPCR family.

<p>The maximum likelihood (ML) optimal tree topology is presented and was constructed with MEGA5. ML bootstrap values higher than 50% are indicated at nodes. To facilitate interpretation, PTHR was used as an outgroup based on the proposed models for secretin GPCR family evolution <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053482#pone.0053482-Cardoso1" target="_blank">[7]</a>. The tree supported the identities of lfGHRHR and xGHRHR₂ as the orthologs of mammalian GHRHR and chicken GHRHR₂ respectively. Accession numbers of the sequences used were listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053482#pone.0053482.s009" target="_blank">Table S2</a>.</p

Gene linkage comparisons of GHRHRs in the Osteichthyes lineage.

<p>Genes in vicinity of GHRHR were mapped, and syntenic genes were linked by straight lines. Size of the chromosomal region analyzed was given underneath based on the current edition of Ensembl databases. Syntenic genes encoding other secretin GPCR receptors were drawn in grey boxes, and the conserved flanking genes of GHRHR were drawn in closed boxes. (A) Gene environment of GHRHR in the Sarcopterygii lineage represented by human, mouse, lizard, chicken, frog and coelacanth was compared. Despite the syntenic genomic locations of GHRHR and neighbouring genes from human to avians, GHRHR was not located in frog. (B) Gene environment of GHRHR in the Actinopterygii lineage represented by fugu, tetraodon, stickleback, medaka, and zebrafish. Apart from the less conserved genomic region of zebrafish GHRHR, genes in proximity of other teleost GHRHRs were highly syntenic. However, they displayed an entirely different gene environment when compared to the sarcopterygian GHRHRs. (C) Genomic location analysis of xGHRHR characterized in present work and GHRHR₂ in zebrafish and chicken. Gene synteny could neither be identified inter-species nor between the two GHRHR genes in the same species. The figures were not drawn to scale.</p