{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,18]],"date-time":"2026-04-18T06:07:53Z","timestamp":1776492473938,"version":"3.51.2"},"reference-count":55,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2022,4,14]],"date-time":"2022-04-14T00:00:00Z","timestamp":1649894400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Endocrinol."],"abstract":"<jats:p>The Hatschek\u2019s pit in the cephalochordate amphioxus, an invertebrate deuterostome basal to chordates is suggested to be the functional homolog structure of the vertebrate adenohypophysis based on anatomy and expression of homologous neuroendocrine genes. However, the endocrine potential of the cephalochordate Hatschek\u2019s pit remains to be demonstrated as well as the physiological actions of the secreted neuropeptides. In this study, we have explored the distribution and characterize the potential function of the amphioxus PACAP\/GCG precursor, which is the ortholog of the hypothalamic PACAP neuropeptide in vertebrates. In amphioxi, two PACAP\/GCG transcripts <jats:italic>PACAP\/GCGa<\/jats:italic> and <jats:italic>PACAP\/GCGbc<\/jats:italic> that are alternative isoforms of a single gene with different peptide coding potentials were isolated. Immunofluorescence staining detected their expression around the nucleus of Rohde, supporting that this structure may be homologous of the neurosecretory cells of the vertebrate hypothalamus where abundant PACAP is found. <jats:italic>PACAP\/GCGa<\/jats:italic> was also detected in the infundibulum\u2010like downgrowth approaching the Hatschek\u2019s pit, indicating diffusion of <jats:italic>PACAP\/GCGa<\/jats:italic> from the CNS to the pit <jats:italic>via<\/jats:italic> the infundibulum\u2010like downgrowth. Under a high salinity challenge, <jats:italic>PACAP\/GCGa<\/jats:italic> was upregulated in amphioxi head and <jats:italic>PACAP\/GCGa<\/jats:italic> treatment increased expression of GHl in Hatschek\u2019s pit in a dose-dependent manner, suggesting that <jats:italic>PACAP\/GCGa<\/jats:italic> may be involved in the regulation of <jats:italic>GHl via<\/jats:italic> hypothalamic-pituitary (HP)-like axis similar as in the vertebrates. Our results support that the amphioxus Hatschek\u2019s pit is likely to be the functional homolog of pituitary gland in vertebrates.<\/jats:p>","DOI":"10.3389\/fendo.2022.850040","type":"journal-article","created":{"date-parts":[[2022,4,14]],"date-time":"2022-04-14T09:23:56Z","timestamp":1649928236000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":7,"title":["PACAP\/GCGa Is an Important Modulator of the Amphioxus CNS-Hatschek\u2019s Pit Axis, the Homolog of the Vertebrate Hypothalamic-Pituitary Axis in the Basal Chordates"],"prefix":"10.3389","volume":"13","author":[{"given":"Jason S. W.","family":"On","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Liuru","family":"Su","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hong","family":"Shen","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Aloysius W. R.","family":"Arokiaraj","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jo\u00e3o C. R.","family":"Cardoso","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Guang","family":"Li","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Billy K. C.","family":"Chow","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1965","published-online":{"date-parts":[[2022,4,14]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"3","DOI":"10.1016\/j.ygcen.2017.10.016","article-title":"Landmark Discoveries in Elucidating the Origins of the Hypothalamic-Pituitary System From the Perspective of a Basal Vertebrate, Sea Lamprey","volume":"264","author":"Sower","year":"2018","journal-title":"Gen Comp Endocrinol"},{"key":"B2","doi-asserted-by":"publisher","first-page":"3","DOI":"10.1016\/j.ygcen.2005.10.011","article-title":"The Dawn and Evolution of Hormones in the Adenohypophysis","volume":"148","author":"Kawauchi","year":"2006","journal-title":"Gen Comp Endocrinol"},{"key":"B3","doi-asserted-by":"publisher","first-page":"53","DOI":"10.1093\/icb\/icq047","article-title":"Evolution of the Reproductive Endocrine System in Chordates","volume":"50","author":"Kubokawa","year":"2010","journal-title":"Integr Comp Biol"},{"key":"B4","doi-asserted-by":"publisher","DOI":"10.1093\/molbev\/mst031","article-title":"Expansion of Secretin-Like G Protein-Coupled Receptors and Their Peptide Ligands via Local Duplications Before and After Two Rounds of Whole-Genome Duplication","volume":"30","author":"Hwang","year":"2013","journal-title":"Mol Biol Evol"},{"key":"B5","doi-asserted-by":"publisher","DOI":"10.1093\/molbev\/mst269","article-title":"At the Transition From Invertebrates to Vertebrates, a Novel GnRH-Like Peptide Emerges in Amphioxus","volume":"31","author":"Roch","year":"2014","journal-title":"Mol Biol Evol"},{"key":"B6","doi-asserted-by":"publisher","DOI":"10.3389\/fendo.2015.00028","article-title":"Evolution of Parathyroid Hormone Receptor Family and Their Ligands in Vertebrate","volume":"6","author":"On","year":"2015","journal-title":"Front Endocrinol"},{"key":"B7","doi-asserted-by":"publisher","DOI":"10.1101\/gr.073676.107","article-title":"The Amphioxus Genome Illuminates Vertebrate Origins and Cephalochordate Biology","volume":"18","author":"Holland","year":"2008","journal-title":"Genome Res"},{"key":"B8","doi-asserted-by":"publisher","DOI":"10.1210\/en.2016-1848","article-title":"Demonstration of a Functional Kisspeptin\/Kisspeptin Receptor System in Amphioxus With Implications for Origin of Neuroendocrine Regulation","volume":"158","author":"Wang","year":"2017","journal-title":"Endocrinology"},{"key":"B9","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.1219956110","article-title":"Molecular Evolution of Peptidergic Signaling Systems in Bilaterians","volume":"110","author":"Mirabeau","year":"2013","journal-title":"Proc Natl Acad Sci USA"},{"key":"B10","doi-asserted-by":"publisher","DOI":"10.1046\/j.1463-6395.1999.00027.x","article-title":"Brain-Hatschek's Pit Relationships in Amphioxus Species","volume":"80","author":"Gorbman","year":"1999","journal-title":"Acta Zoologica"},{"key":"B11","doi-asserted-by":"publisher","DOI":"10.1210\/en.2014-1377","article-title":"Functional Characterization of GH-Like Homolog in Amphioxus Reveals an Ancient Origin of GH\/GH Receptor System","volume":"155","author":"Li","year":"2014","journal-title":"Endocrinology"},{"key":"B12","doi-asserted-by":"publisher","DOI":"10.1093\/molbev\/msv087","article-title":"Functional Pairing of Class B1 Ligand-GPCR in Cephalochordate Provides Evidence of the Origin of PTH and PACAP\/Glucagon Receptor Family","volume":"32","author":"On","year":"2015","journal-title":"Mol Biol Evol"},{"key":"B13","doi-asserted-by":"publisher","DOI":"10.3389\/fnins.2020.00366","article-title":"Tracing the Origins of the Pituitary Adenylate-Cyclase Activating Polypeptide (PACAP)","volume":"14","author":"Cardoso","year":"2020","journal-title":"Front Neurosci"},{"key":"B14","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.0611397104","article-title":"Solution Structure and Mutational Analysis of Pituitary Adenylate Cyclase-Activating Polypeptide Binding to the Extracellular Domain of PAC1-Rs","volume":"104","author":"Sun","year":"2007","journal-title":"Proc Natl Acad Sci USA"},{"key":"B15","doi-asserted-by":"publisher","DOI":"10.1021\/jm900291j","article-title":"Molecular and Conformational Determinants of Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) for Activation of the PAC1 Receptor","volume":"52","author":"Bourgault","year":"2009","journal-title":"J Medicinal Chem"},{"key":"B16","doi-asserted-by":"publisher","DOI":"10.1016\/j.biochi.2010.12.010","article-title":"Identification by Photoaffinity Labeling of the Extracellular N-Terminal Domain of PAC1 Receptor as the Major Binding Site for PACAP","volume":"93","author":"Dejda","year":"2011","journal-title":"Biochimie"},{"key":"B17","doi-asserted-by":"publisher","DOI":"10.1016\/j.peptides.2007.05.016","article-title":"PACAP, VIP and Their Receptors in the Metazoa: Insights About the Origin and Evolution of the Ligand\u2013Receptor Pair","volume":"28","author":"Cardoso","year":"2007","journal-title":"Peptides"},{"key":"B18","doi-asserted-by":"publisher","DOI":"10.1186\/1471-2148-10-135","article-title":"The Serendipitous Origin of Chordate Secretin Peptide Family Members","volume":"10","author":"Cardoso","year":"2010","journal-title":"BMC Evol Biol"},{"key":"B19","doi-asserted-by":"publisher","DOI":"10.1210\/edrv.21.6.0414","article-title":"The Origin and Function of the Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP)\/glucagon Superfamily","volume":"21","author":"Sherwood","year":"2000","journal-title":"Endocrine Rev"},{"key":"B20","doi-asserted-by":"publisher","first-page":"283","DOI":"10.1124\/pr.109.001370","article-title":"Pituitary Adenylate Cyclase-Activating Polypeptide and its Receptors: 20 Years After the Discovery","volume":"61","author":"Vaudry","year":"2009","journal-title":"Pharmacol Rev"},{"key":"B21","doi-asserted-by":"publisher","first-page":"269","DOI":"10.1124\/pr.109.001370","article-title":"Pituitary Adenylate Cyclase-Activating Polypeptide and its Receptors: From Structure to Functions","volume":"52","author":"Vaudry","year":"2000","journal-title":"Pharmacol Rev"},{"key":"B22","doi-asserted-by":"publisher","DOI":"10.1210\/endo-129-5-2787","article-title":"Tissue Distribution of Pacap as Determined by Ria - Highly Abundant in the Rat-Brain and Testes","volume":"129","author":"Arimura","year":"1991","journal-title":"Endocrinology"},{"key":"B23","doi-asserted-by":"publisher","DOI":"10.1677\/joe.0.1360159","article-title":"Distribution, Molecular Characterization of Pituitary Adenylate Cyclase-Activating Polypeptide and Its Precursor Encoding Messenger RNA in Human and Rat Tissues","volume":"136","author":"Ghatei","year":"1993","journal-title":"J Endocrinol"},{"key":"B24","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1186\/s10194-018-0855-1","article-title":"Discovery of PACAP and its Receptors in the Brain","volume":"19","author":"Hirabayashi","year":"2018","journal-title":"J Headache Pain"},{"key":"B25","doi-asserted-by":"publisher","DOI":"10.1177\/0333102419893962","article-title":"Cellular Distribution of PACAP-38 and PACAP Receptors in the Rat Brain: Relation to Migraine Activated Regions","volume":"40","author":"Warfvinge","year":"2020","journal-title":"Cephalalgia"},{"key":"B26","doi-asserted-by":"publisher","DOI":"10.1155\/2017\/9538685","article-title":"Activities of Amphioxus GH-Like Protein in Osmoregulation: Insight Into Origin of Vertebrate GH Family","volume":"2017","author":"Li","year":"2017","journal-title":"Int J Endocrinol"},{"key":"B27","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0099264","article-title":"Year-Round Reproduction and Induced Spawning of Chinese Amphioxus, Branchiostoma Belcheri, in Laboratory","volume":"9","author":"Li","year":"2014","journal-title":"PloS One"},{"key":"B28","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0050838","article-title":"Consecutive Spawnings of Chinese Amphioxus, Branchiostoma Belcheri, in Captivity","volume":"7","author":"Li","year":"2012","journal-title":"PloS One"},{"key":"B29","doi-asserted-by":"publisher","DOI":"10.1016\/j.fsi.2012.03.001","article-title":"Ef1\u03b1 Is a Useful Internal Reference for Studies of Gene Expression Regulation in Amphioxus Branchiostoma Japonicum","volume":"32","author":"Wang","year":"2012","journal-title":"Fish Shellfish Immunol"},{"key":"B30","doi-asserted-by":"publisher","DOI":"10.1006\/meth.2001.1262","article-title":"Analysis of Relative Gene Expression Data Using Real-Time Quantitative PCR and the 2(T)(-Delta Delta C) Method","volume":"25","author":"Livak","year":"2001","journal-title":"Methods"},{"key":"B31","doi-asserted-by":"publisher","first-page":"pdb prot5286","DOI":"10.1101\/pdb.prot5286","article-title":"Amphioxus Whole-Mount in Situ Hybridization","volume":"2009","author":"Yu","year":"2009","journal-title":"Cold Spring Harb Protoc"},{"key":"B32","doi-asserted-by":"publisher","DOI":"10.1139\/z04-163","article-title":"The Nervous System of Amphioxus: Structure, Development, and Evolutionary Significance","volume":"83","author":"Wicht","year":"2005","journal-title":"Can J Zoology"},{"key":"B33","doi-asserted-by":"publisher","DOI":"10.1002\/cne.23785","article-title":"Neuronal Organization of the Brain in the Adult Amphioxus (Branchiostoma Lanceolatum): A Study With Acetylated Tubulin Immunohistochemistry","volume":"523","author":"Castro","year":"2015","journal-title":"J Comp Neurol"},{"key":"B34","doi-asserted-by":"publisher","DOI":"10.1006\/gcen.1994.1194","article-title":"Diffusion Between the Neurohypophysis and the Adenohypophysis of Lampreys, Petromyzon Marinus","volume":"96","author":"Nozaki","year":"1994","journal-title":"Gen Comp Endocrinol"},{"key":"B35","doi-asserted-by":"publisher","DOI":"10.1006\/gcen.1998.7193","article-title":"A Brain-Hatschek's Pit Connection in Amphioxus","volume":"113","author":"Gorbman","year":"1999","journal-title":"Gen Comp Endocrinol"},{"key":"B36","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.0900708106","article-title":"Light-Transduction in Melanopsin-Expressing Photoreceptors of Amphioxus","volume":"106","author":"Gomez Mdel","year":"2009","journal-title":"Proc Natl Acad Sci USA"},{"key":"B37","doi-asserted-by":"publisher","first-page":"Rc191","DOI":"10.1523\/JNEUROSCI.22-01-j0002.2002","article-title":"The Photopigment Melanopsin Is Exclusively Present in Pituitary Adenylate Cyclase-Activating Polypeptide-Containing Retinal Ganglion Cells of the Retinohypothalamic Tract","volume":"22","author":"Hannibal","year":"2002","journal-title":"J Neurosci"},{"key":"B38","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1677\/joe.0.1430001","article-title":"Effect of Pituitary Adenylate Cyclase-Activating Polypeptide 38 on Growth Hormone and Prolactin Expression","volume":"143","author":"Velkeniers","year":"1994","journal-title":"J Endocrinol"},{"key":"B39","doi-asserted-by":"publisher","DOI":"10.1046\/j.1365-2826.1999.00334.x","article-title":"Evidence That Corticotropin-Releasing Hormone Acts as a Growth Hormone-Releasing Factor in a Primitive Teleost, the European Eel (Anguilla Anguilla)","volume":"11","author":"Rousseau","year":"1999","journal-title":"J\u00a0Neuroendocrinol"},{"key":"B40","doi-asserted-by":"publisher","DOI":"10.1677\/jme.0.0250157","article-title":"Molecular Evolution of the Growth Hormone-Releasing Hormone\/Pituitary Adenylate Cyclase-Activating Polypeptide Gene Family. Functional Implication in the Regulation of Growth Hormone Secretion","volume":"25","author":"Montero","year":"2000","journal-title":"J Mol Endocrinol"},{"key":"B41","doi-asserted-by":"publisher","DOI":"10.1210\/en.2005-1534","article-title":"Identification of the Chicken Growth Hormone-Releasing Hormone Receptor (GHRH-R) mRNA and Gene: Regulation of Anterior Pituitary GHRH-R mRNA Levels by Homologous and Heterologous Hormones","volume":"147","author":"Porter","year":"2006","journal-title":"Endocrinology"},{"key":"B42","doi-asserted-by":"publisher","DOI":"10.1016\/j.ygcen.2007.05.007","article-title":"Differential Involvement of Nitric Oxide Signaling in Dopamine and PACAP Stimulation of Growth Hormone Release in Goldfish","volume":"155","author":"Mitchell","year":"2008","journal-title":"Gen Comp Endocrinol"},{"key":"B43","doi-asserted-by":"publisher","DOI":"10.1111\/j.1463-6395.1986.tb00864.x","article-title":"The Wheel Organ and Hatschek's Groove in the Lancelet, Branchiostoma Lanceolatum (Cephalochordata)","volume":"67","author":"Sahlin","year":"1986","journal-title":"Acta Zoologica"},{"key":"B44","doi-asserted-by":"crossref","DOI":"10.1007\/978-3-319-35135-3_1","article-title":"Molecular Evolution of Pituitary Adenylyl Cyclase-Activating Polypeptide Subfamily and Cognate Receptor Subfamily","volume-title":"Pituitary Adenylate Cyclase Activating Polypeptide\u2014PACAP","author":"On","year":"2016"},{"key":"B45","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1186\/1471-2148-10-135","article-title":"The Serendipitous Origin of Chordate Secretin Peptide Family Members","volume":"10","author":"Cardoso","year":"2010","journal-title":"BMC evolutionary Biol"},{"key":"B46","doi-asserted-by":"publisher","DOI":"10.1007\/s00441-018-2958-z","article-title":"Two Ancient Neuropeptides, PACAP and AVP, Modulate Motivated Behavior at Synapses in the Extrahypothalamic Brain: A Study in Contrast","volume":"375","author":"Zhang","year":"2019","journal-title":"Cell Tissue Res"},{"key":"B47","doi-asserted-by":"publisher","first-page":"8682","DOI":"10.3390\/ijms22168682","article-title":"Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) in Physiological and Pathological Processes Within the Gastrointestinal Tract: A Review","volume":"22","author":"Karpiesiuk","year":"2021","journal-title":"Int J Mol Sci"},{"key":"B48","doi-asserted-by":"publisher","DOI":"10.1007\/bf00226606","article-title":"Electron Microscopical Observations on K\u00f6lliker's and Hatschek's Pit and on the Wheel Organ in the Head Region of Amphioxus (Branchiostoma Lanceolatum)","volume":"153","author":"Tjoa","year":"1974","journal-title":"Cell Tissue Res"},{"key":"B49","doi-asserted-by":"publisher","first-page":"32","DOI":"10.1002\/jez.b.44","article-title":"Development of the Adenohypophysis in the Lamprey: Evolution of Epigenetic Patterning Programs in Organogenesis","volume":"300","author":"Uchida","year":"2003","journal-title":"J Exp Zool B Mol Dev Evol"},{"key":"B50","article-title":"Distribution of Prolactin and PRL Receptor-Like Immunoreactivities in the Nervous System, Hatschek\u2019s Pit and Other Tissues of Amphioxus Branchiostoma Belcheri","volume":"52","author":"Weng","year":"2006","journal-title":"Acta Zool Sin"},{"key":"B51","article-title":"The Question of Functional Homology of Hatschek's Pit of Amphioxus (Branchiostoma Belcheri) and the Vertebrate Adenohypophysis","volume":"9","author":"Nozaki","year":"1992","journal-title":"Zoological Sci"},{"key":"B52","doi-asserted-by":"publisher","DOI":"10.1016\/j.brainresbull.2007.10.023","article-title":"Expression of the Amphioxus Pit-1 Gene (AmphiPOU1F1\/Pit-1) Exclusively in the Developing Preoral Organ, a Putative Homolog of the Vertebrate Adenohypophysis","volume":"75","author":"Candiani","year":"2008","journal-title":"Brain Res Bull"},{"key":"B53","doi-asserted-by":"publisher","DOI":"10.1016\/j.peptides.2007.07.011","article-title":"PACAP-Related Peptide (PRP)\u2014molecular Evolution and Potential Functions","volume":"28","author":"Tam","year":"2007","journal-title":"Peptides"},{"key":"B54","doi-asserted-by":"publisher","DOI":"10.1210\/endo.138.1.4830","article-title":"Exon Skipping in the Gene Encoding Pituitary Adenylate Cyclase-Activating Polypeptide in Salmon Alters the Expression of Two Hormones That Stimulate Growth Hormone Release","volume":"138","author":"Parker","year":"1997","journal-title":"Endocrinology"},{"key":"B55","doi-asserted-by":"publisher","DOI":"10.1210\/endo.139.10.6239","article-title":"Distribution, Characterization, and Growth Hormone-Releasing Activity of Pituitary Adenylate Cyclase-Activating Polypeptide in the European Eel, Anguilla Anguilla","volume":"139","author":"Montero","year":"1998","journal-title":"Endocrinology"}],"container-title":["Frontiers in Endocrinology"],"original-title":[],"link":[{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fendo.2022.850040\/full","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2022,4,14]],"date-time":"2022-04-14T09:24:03Z","timestamp":1649928243000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fendo.2022.850040\/full"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,4,14]]},"references-count":55,"alternative-id":["10.3389\/fendo.2022.850040"],"URL":"https:\/\/doi.org\/10.3389\/fendo.2022.850040","relation":{},"ISSN":["1664-2392"],"issn-type":[{"value":"1664-2392","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,4,14]]},"article-number":"850040"}}