{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,17]],"date-time":"2026-02-17T14:35:17Z","timestamp":1771338917144,"version":"3.50.1"},"reference-count":57,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2023,7,31]],"date-time":"2023-07-31T00:00:00Z","timestamp":1690761600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:p>Male pregnancy in syngnathids (seahorses, pipefishes, and sea dragons) is an evolutionary innovation in the animal kingdom. Paternal immune resistance to the fetus is a critical challenge, particularly in seahorses with fully enclosed brood pouches and sophisticated placentas. In this study, comparative genomic analysis revealed that all syngnathid species lost three vertebrate-conserved <jats:italic>Toll-like receptors<\/jats:italic> (<jats:italic>TLR1, TLR2<\/jats:italic>, and <jats:italic>TLR9<\/jats:italic>), of which all play essential roles in immune protection and immune tolerance in the uterus and placenta. Quantitative real-time PCR (qRT-PCR) analysis showed that the <jats:italic>TLR<\/jats:italic> paralog genes including <jats:italic>TLR18<\/jats:italic>, <jats:italic>TLR25<\/jats:italic>, and <jats:italic>TLR21<\/jats:italic> were highly expressed in the placenta inside the seahorse brood pouch and changed dynamically during the breeding cycle, suggesting the potentially important role of the <jats:italic>TLR<\/jats:italic>s during male pregnancy. Furthermore, the immune challenge test <jats:italic>in vitro<\/jats:italic> showed a remarkable expression response from all three <jats:italic>TLR<\/jats:italic> genes to specific pathogenic antigens, confirming their immune function in seahorse brood pouches. Notably, the altered antigen recognition spectrum of these genes appeared to functionally compensate in part for the lost TLRs, in contrast to that observed in other species. Therefore, we suggest that gene loss and co-option of <jats:italic>TLR<\/jats:italic>s may be a typical evolutionary strategy for facilitating paternal immunological adaptation during male pregnancy.<\/jats:p>","DOI":"10.3389\/fimmu.2023.1224698","type":"journal-article","created":{"date-parts":[[2023,7,31]],"date-time":"2023-07-31T11:32:28Z","timestamp":1690803148000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":1,"title":["Gene loss and co-option of toll-like receptors facilitate paternal immunological adaptation in the brood pouch of pregnant male seahorses"],"prefix":"10.3389","volume":"14","author":[{"given":"Bo","family":"Zhang","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Wanghong","family":"Xiao","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Geng","family":"Qin","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zelin","family":"Chen","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lihua","family":"Qiu","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xin","family":"Wang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Qiang","family":"Lin","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1965","published-online":{"date-parts":[[2023,7,31]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","DOI":"10.1016\/j.earlhumdev.2014.08.013","article-title":"The evolution of pregnancy","volume":"90","author":"Bainbridge","year":"2014","journal-title":"Early Hum Dev"},{"key":"B2","doi-asserted-by":"publisher","DOI":"10.1016\/j.ogc.2016.07.004","article-title":"Immune regulation in pregnancy: a matter of perspective","volume":"43","author":"Bonney","year":"2016","journal-title":"Obstetrics Gynecol Clinics"},{"key":"B3","doi-asserted-by":"publisher","DOI":"10.1016\/S0300-483X(02)00607-8","article-title":"Pregnancy and the immune system: between tolerance and rejection","volume":"185","author":"Thellin","year":"2003","journal-title":"Toxicology"},{"key":"B4","doi-asserted-by":"publisher","DOI":"10.1111\/mec.16333","article-title":"Immunological tolerance in the evolution of male pregnancy","volume":"32","author":"Parker","year":"2023","journal-title":"Mol Ecol"},{"key":"B5","doi-asserted-by":"publisher","first-page":"7610","DOI":"10.1038\/s41467-022-35338-7","article-title":"Immunogenetic losses co-occurred with seahorse male pregnancy and mutation in tlx1 accompanied functional asplenia","volume":"13","author":"Liu","year":"2022","journal-title":"Nat Commun"},{"key":"B6","doi-asserted-by":"publisher","DOI":"10.1007\/s11427-022-2317-6","article-title":"The genetic basis of the leafy seadragon\u2019s unique camouflage morphology and avenues for its efficient conservation derived from habitat modeling","volume":"66","author":"Qu","year":"2023","journal-title":"Sci China Life Sci"},{"key":"B7","doi-asserted-by":"publisher","first-page":"19","DOI":"10.1186\/s40851-017-0080-9","article-title":"Morphology of brood pouch formation in the pot-bellied seahorse Hippocampus abdominalis","volume":"3","author":"Kawaguchi","year":"2017","journal-title":"Zool Lett"},{"key":"B8","doi-asserted-by":"publisher","DOI":"10.1093\/nsr\/nwaa002","article-title":"Comparative genomics reveal shared genomic changes in syngnathid fishes and signatures of genetic convergence with placental mammals","volume":"7","author":"Zhang","year":"2020","journal-title":"Natl Sci Rev"},{"key":"B9","doi-asserted-by":"publisher","first-page":"497","DOI":"10.1071\/MF05112","article-title":"Alteration of the brood pouch morphology during gestation of male seahorses, Hippocampus kuda","volume":"57","author":"Laksanawimol","year":"2006","journal-title":"Mar Freshw Res"},{"key":"B10","doi-asserted-by":"publisher","DOI":"10.1093\/molbev\/msv177","article-title":"Seahorse brood pouch transcriptome reveals common genes associated with vertebrate pregnancy","volume":"32","author":"Whittington","year":"2015","journal-title":"Mol Biol Evol"},{"key":"B11","doi-asserted-by":"publisher","DOI":"10.1038\/nature20595","article-title":"The seahorse genome and the evolution of its specialized morphology","volume":"540","author":"Lin","year":"2016","journal-title":"Nature"},{"key":"B12","doi-asserted-by":"publisher","first-page":"736628","DOI":"10.1016\/j.aquaculture.2021.736628","article-title":"Molecular characterization of TLR22 and its role in immunological modification of the brood pouch of the lined seahorse, Hippocampus erectus","volume":"539","author":"Wu","year":"2021","journal-title":"Aquaculture"},{"key":"B13","doi-asserted-by":"publisher","DOI":"10.3389\/fimmu.2022.884417","article-title":"Hepcidin gene Co-option balancing paternal immune protection and Male pregnancy","volume":"13","author":"Xiao","year":"2022","journal-title":"Front Immunol"},{"key":"B14","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.1916251117","article-title":"Evolution of male pregnancy associated with remodeling of canonical vertebrate immunity in seahorses and pipefishes","volume":"117","author":"Roth","year":"2020","journal-title":"Proc Natl Acad Sci"},{"key":"B15","doi-asserted-by":"publisher","first-page":"100185","DOI":"10.1016\/j.xinn.2021.100185","article-title":"Genomic basis of evolutionary adaptation in a warm-blooded fish","volume":"3","author":"Wang","year":"2022","journal-title":"Innovation"},{"key":"B16","article-title":"Male Pregnancy and the evolutionary importance of immunological tolerance in syngnathid fishes","author":"Parker","year":"2021"},{"key":"B17","doi-asserted-by":"publisher","DOI":"10.1002\/bies.20626","article-title":"Male Pregnancy in seahorses and pipefish: beyond the mammalian model","volume":"29","author":"St\u00f6lting","year":"2007","journal-title":"BioEssays"},{"key":"B18","doi-asserted-by":"publisher","DOI":"10.1038\/nrg2303","article-title":"Toll-like receptors\u2013taking an evolutionary approach","volume":"9","author":"Leulier","year":"2008","journal-title":"Nat Rev Genet"},{"key":"B19","doi-asserted-by":"publisher","first-page":"e12771","DOI":"10.1111\/sji.12771","article-title":"Toll-like receptor polymorphism in host immune response to infectious diseases: a review","volume":"90","author":"Mukherjee","year":"2019","journal-title":"Scandinavian J Immunol"},{"key":"B20","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.0502272102","article-title":"The evolution of vertebrate toll-like receptors","volume":"102","author":"Roach","year":"2005","journal-title":"Proc Natl Acad Sci"},{"key":"B21","doi-asserted-by":"publisher","DOI":"10.1016\/j.dci.2013.08.010","article-title":"Ligand specificities of toll-like receptors in fish: indications from infection studies","volume":"43","author":"Pietretti","year":"2014","journal-title":"Dev Comp Immunol"},{"key":"B22","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1186\/1471-2148-12-256","article-title":"Diversification of the expanded teleost-specific toll-like receptor family in Atlantic cod, gadus morhua","volume":"12","author":"Sundaram","year":"2012","journal-title":"BMC Evolutionary Biol"},{"key":"B23","doi-asserted-by":"publisher","DOI":"10.1016\/j.molimm.2009.06.002","article-title":"Chicken TLR21 acts as a functional homologue to mammalian TLR9 in the recognition of CpG oligodeoxynucleotides","volume":"46","author":"Brownlie","year":"2009","journal-title":"Mol Immunol"},{"key":"B24","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.1305273110","article-title":"Toll-like receptor 9 and 21 have different ligand recognition profiles and cooperatively mediate activity of CpG-oligodeoxynucleotides in zebrafish","volume":"110","author":"Yeh","year":"2013","journal-title":"Proc Natl Acad Sci"},{"key":"B25","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1016\/j.placenta.2016.07.005","article-title":"Differential expression of toll-like receptors in the human placenta across early gestation","volume":"46","author":"Pudney","year":"2016","journal-title":"Placenta"},{"key":"B26","doi-asserted-by":"publisher","DOI":"10.17192\/z2010.0376","article-title":"The role of toll-like receptors in the development of immunological tolerance in neonates","author":"Patrascan","year":"2010"},{"key":"B27","doi-asserted-by":"publisher","first-page":"192","DOI":"10.1111\/aji.12258","article-title":"Toll-like receptors at the maternal-fetal interface in normal pregnancy and pregnancy complications","volume":"72","author":"Koga","year":"2014","journal-title":"Am J Reprod Immunol"},{"key":"B28","doi-asserted-by":"publisher","DOI":"10.1038\/nri3095","article-title":"TLR-dependent T cell activation in autoimmunity","volume":"11","author":"Mills","year":"2011","journal-title":"Nat Rev Immunol"},{"key":"B29","doi-asserted-by":"publisher","first-page":"7","DOI":"10.1016\/j.cell.2012.06.020","article-title":"Maternal-fetal immune tolerance, block by block","volume":"150","author":"Gobert","year":"2012","journal-title":"Cell"},{"key":"B30","doi-asserted-by":"publisher","first-page":"587","DOI":"10.1111\/j.1600-0897.2010.00848.x","article-title":"Toll-like receptors at the maternal\u2013fetal interface in normal pregnancy and pregnancy disorders","volume":"63","author":"Koga","year":"2010","journal-title":"Am J Reprod Immunol"},{"key":"B31","doi-asserted-by":"publisher","first-page":"25","DOI":"10.1016\/j.theriogenology.2018.01.010","article-title":"Expression patterns of toll-like receptors in the ovine corpus luteum during the early pregnancy and prostaglandin F2\u03b1-induced luteolysis","volume":"111","author":"Atli","year":"2018","journal-title":"Theriogenology"},{"key":"B32","doi-asserted-by":"publisher","DOI":"10.1016\/j.placenta.2004.08.010","article-title":"Toll-like receptors and their role in the trophoblast","volume":"26","author":"Abrahams","year":"2005","journal-title":"Placenta"},{"key":"B33","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.1710470114","article-title":"Integrative single-cell and cell-free plasma RNA transcriptomics elucidates placental cellular dynamics","volume":"114","author":"Tsang","year":"2017","journal-title":"PNAS"},{"key":"B34","doi-asserted-by":"publisher","DOI":"10.1016\/j.cell.2020.02.041","article-title":"Toll-like receptors and the control of immunity","volume":"180","author":"Fitzgerald","year":"2020","journal-title":"Cell"},{"key":"B35","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1186\/1471-2164-9-62","article-title":"Evolution of the chicken toll-like receptor gene family: a story of gene gain and gene loss","volume":"9","author":"Temperley","year":"2008","journal-title":"BMC Genomics"},{"key":"B36","doi-asserted-by":"publisher","first-page":"131","DOI":"10.3390\/d11080131","article-title":"The vertebrate TLR supergene family evolved dynamically by gene gain\/loss and positive selection revealing a host\u2013pathogen arms race in birds","volume":"11","author":"Khan","year":"2019","journal-title":"Diversity"},{"key":"B37","doi-asserted-by":"publisher","DOI":"10.1016\/j.dci.2011.03.006","article-title":"Toll-like receptors in bony fish: from genomics to function","volume":"35","author":"Palti","year":"2011","journal-title":"Dev Comp Immunol"},{"key":"B38","doi-asserted-by":"publisher","first-page":"25211","DOI":"10.1038\/srep25211","article-title":"Evolutionary redesign of the Atlantic cod (Gadus morhua L.) toll-like receptor repertoire by gene losses and expansions","volume":"6","author":"Solbakken","year":"2016","journal-title":"Sci Rep"},{"key":"B39","doi-asserted-by":"publisher","first-page":"100052","DOI":"10.1016\/j.xinn.2020.100052","article-title":"Regulatory role of retinoic acid in male pregnancy of the seahorse","volume":"1","author":"Li","year":"2020","journal-title":"Innovation"},{"key":"B40","doi-asserted-by":"publisher","DOI":"10.1016\/j.coi.2003.09.002","article-title":"Toll-like receptors: balancing host resistance with immune tolerance","volume":"15","author":"Pasare","year":"2003","journal-title":"Curr Opin Immunol"},{"key":"B41","doi-asserted-by":"publisher","DOI":"10.1016\/j.meegid.2010.05.005","article-title":"The toll-like receptor 1 variant S248N influences placental malaria","volume":"10","author":"Hamann","year":"2010","journal-title":"Infect Genet Evol"},{"key":"B42","doi-asserted-by":"publisher","DOI":"10.1080\/09674845.2019.1687151","article-title":"Links between SNPs in TLR-2 and TLR-4 and idiopathic recurrent pregnancy loss","volume":"77","author":"Bahia","year":"2020","journal-title":"Br J Biomed Sci"},{"key":"B43","doi-asserted-by":"publisher","DOI":"10.4049\/jimmunol.0900788","article-title":"TLR9 activation coupled to IL-10 deficiency induces adverse pregnancy outcomes","volume":"183","author":"Thaxton","year":"2009","journal-title":"J Immunol"},{"key":"B44","doi-asserted-by":"publisher","DOI":"10.1016\/j.intimp.2015.11.004","article-title":"Excessive TLR9 signaling contributes to the pathogenesis of spontaneous abortion through impairment of treg cell survival by activation of caspase 8\/3","volume":"29","author":"Kang","year":"2015","journal-title":"Int Immunopharmacol"},{"key":"B45","doi-asserted-by":"publisher","first-page":"692","DOI":"10.1016\/j.immuni.2010.04.010","article-title":"Toll-like receptor 2 signaling in CD4(+) T lymphocytes promotes T helper 17 responses and regulates the pathogenesis of autoimmune disease","volume":"32","author":"Reynolds","year":"2010","journal-title":"Immunity"},{"key":"B46","doi-asserted-by":"publisher","DOI":"10.1046\/j.1365-2567.2002.01491.x","article-title":"Expression and regulation of the pattern recognition receptors toll-like receptor-2 and toll-like receptor-4 in the human placenta","volume":"107","author":"Holmlund","year":"2002","journal-title":"Immunology"},{"key":"B47","doi-asserted-by":"publisher","DOI":"10.1002\/eji.200425336","article-title":"Binding of lipopeptide to CD14 induces physical proximity of CD14, TLR2 and TLR1","volume":"35","author":"Manukyan","year":"2005","journal-title":"Eur J Immunol"},{"key":"B48","doi-asserted-by":"publisher","DOI":"10.1016\/j.fsi.2014.09.022","article-title":"Toll-like receptor recognition of bacteria in fish: ligand specificity and signal pathways","volume":"41","author":"Zhang","year":"2014","journal-title":"Fish Shellfish Immunol"},{"key":"B49","doi-asserted-by":"publisher","DOI":"10.4049\/jimmunol.0900990","article-title":"Evolution of recognition of ligands from gram-positive bacteria: similarities and differences in the TLR2-mediated response between mammalian vertebrates and teleost fish","volume":"184","author":"Ribeiro","year":"2010","journal-title":"J Immunol"},{"key":"B50","doi-asserted-by":"publisher","DOI":"10.1016\/j.vetimm.2011.02.016","article-title":"Cloning and expression of toll-like receptors 1 and 2 from a teleost fish, the orange-spotted grouper Epinephelus coioides","volume":"141","author":"Wei","year":"2011","journal-title":"Vet Immunol Immunopathol"},{"key":"B51","doi-asserted-by":"publisher","DOI":"10.1111\/jfd.13006","article-title":"TLR2 gene in seahorse brood pouch plays key functional roles in LPS-induced antibacterial responses","volume":"42","author":"Zhang","year":"2019","journal-title":"J Fish Dis"},{"key":"B52","doi-asserted-by":"publisher","DOI":"10.1007\/s42995-021-00099-7","article-title":"Wnt8a is one of the candidate genes that play essential roles in the elongation of the seahorse prehensile tail","volume":"3","author":"Zhang","year":"2021","journal-title":"Mar Life Sci Technol"},{"key":"B53","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1093\/gigascience\/gix030","article-title":"Draft genome of the lined seahorse, Hippocampus erectus","volume":"6","author":"Lin","year":"2017","journal-title":"GigaScience"},{"key":"B54","doi-asserted-by":"publisher","first-page":"136840","DOI":"10.1016\/j.scitotenv.2020.136840","article-title":"Environmental estrogens and progestins disturb testis and brood pouch development with modifying transcriptomes in male-pregnancy lined seahorse Hippocampus erectus","volume":"715","author":"Qin","year":"2020","journal-title":"Sci Total Environ"},{"key":"B55","doi-asserted-by":"publisher","first-page":"1094","DOI":"10.1038\/s41467-021-21379-x","article-title":"Genome sequences reveal global dispersal routes and suggest convergent genetic adaptations in seahorse evolution","volume":"12","author":"Li","year":"2021","journal-title":"Nat Commun"},{"key":"B56","doi-asserted-by":"publisher","DOI":"10.1126\/sciadv.abg5196","article-title":"Seadragon genome analysis provides insights into its phenotype and sex determination locus","volume":"7","author":"Qu","year":"2021","journal-title":"Sci Adv"},{"key":"B57","doi-asserted-by":"publisher","DOI":"10.1038\/nprot.2008.73","article-title":"Analyzing real-time PCR data by the comparative CT method","volume":"3","author":"Schmittgen","year":"2008","journal-title":"Nat Protoc"}],"container-title":["Frontiers in Immunology"],"original-title":[],"link":[{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fimmu.2023.1224698\/full","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,7,31]],"date-time":"2023-07-31T11:32:33Z","timestamp":1690803153000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fimmu.2023.1224698\/full"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,7,31]]},"references-count":57,"alternative-id":["10.3389\/fimmu.2023.1224698"],"URL":"https:\/\/doi.org\/10.3389\/fimmu.2023.1224698","relation":{},"ISSN":["1664-3224"],"issn-type":[{"value":"1664-3224","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,7,31]]},"article-number":"1224698"}}