title: Integrated gene mapping and synteny studies give insights into the evolution of a sex proto-chromosome in Solea senegalensis.
abstract: The evolution of genes related to sex and reproduction in fish shows high plasticity and, to date, the sex determination system has only been identified in a few species. Solea senegalensis has 42 chromosomes and an XX/XY chromosome system for sex determination, while related species show the ZZ/ZW system. Next-generation sequencing (NGS), multi-color fluorescence in situ hybridization (mFISH) techniques, and bioinformatics analysis have been carried out, with the objective of revealing new information about sex determination and reproduction in S. senegalensis. To that end, several bacterial artificial chromosome (BAC) clones that contain candidate genes involved in such processes (dmrt1, dmrt2, dmrt3, dmrt4, sox3, sox6, sox8, sox9, lh, cyp19a1a, amh, vasa, aqp3, and nanos3) were analyzed and compared with the same region in other related species. Synteny studies showed that the co-localization of dmrt1-dmrt2-drmt3 in the largest metacentric chromosome of S. senegalensis is coincident with that found in the Z chromosome of Cynoglossus semilaevis, which would potentially make this a sex proto-chromosome. Phylogenetic studies show the close proximity of S. senegalensis to Oryzias latipes, a species with an XX/XY system and a sex master gene. Comparative mapping provides evidence of the preferential association of these candidate genes in particular chromosome pairs. By using the NGS and mFISH techniques, it has been possible to obtain an integrated genetic map, which shows that 15 out of 21 chromosome pairs of S. senegalensis have at least one BAC clone. This result is important for distinguishing those chromosome pairs of S. senegalensis that are similar in shape and size. The mFISH analysis shows the following co-localizations in the same chromosomes: dmrt1-dmrt2-dmrt3, dmrt4-sox9-thrb, aqp3-sox8, cyp19a1a-fshb, igsf9b-sox3, and lysg-sox6.
authors.affiliation: Área de Genética, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, 11510, Cádiz, Spain.
authors.forename: Silvia
authors.initials: S
authors.lastname: Portela-Bens
authors.affiliation: Área de Genética, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, 11510, Cádiz, Spain.
authors.forename: Manuel Alejandro
authors.initials: MA
authors.lastname: Merlo
authors.affiliation: Área de Genética, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, 11510, Cádiz, Spain.
authors.forename: María Esther
authors.initials: ME
authors.lastname: Rodríguez
authors.affiliation: Área de Genética, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, 11510, Cádiz, Spain.
authors.forename: Ismael
authors.initials: I
authors.lastname: Cross
authors.affiliation: Centro IFAPA "El Toruño", 11500, Puerto de Santa María, Cádiz, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Manchado
authors.affiliation: Institut für Humangenetik, Universitätsklinikum Jena, 07743, Jena, Germany.
authors.forename: Nadezda
authors.initials: N
authors.lastname: Kosyakova
authors.affiliation: Institut für Humangenetik, Universitätsklinikum Jena, 07743, Jena, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Liehr
authors.affiliation: Área de Genética, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, 11510, Cádiz, Spain. laureana.rebordinos@uca.es.
authors.forename: Laureana
authors.initials: L
authors.lastname: Rebordinos
mesh_terms: D000818:Animals; D002874:Chromosome Mapping; D022202:Chromosomes, Artificial, Bacterial; D019295:Computational Biology / Q000379:methods; D005399:Fishes / Q000145:classification / Q000235:genetics*; D023281:Genomics / Q000379:methods; D059014:High-Throughput Nucleotide Sequencing; D017404:In Situ Hybridization, Fluorescence; D010802:Phylogeny; D020161:Physical Chromosome Mapping; D012730:Sex Chromosomes; D026801:Synteny
keywords: Bacterial artificial chromosome (BAC); Integrated genetic maps; Multicolor fluorescence in situ hybridization (mFISH); Sex phenotype; Solea senegalensis