title: Evolutionary history and epigenetic regulation of the three paralogous pax7 genes in rainbow trout.
abstract: The extraordinary muscle growth potential of teleost fish, particular those of the Salmoninae clade, elicits questions about the regulation of the relatively highly conserved transcription factors of the myogenic program. The pseudotetraploid nature of the salmonid genome adds another layer of regulatory complexity that must be reconciled with epigenetic data to improve our understanding of the achievement of lifelong muscle growth in these fish. We identify three paralogous pax7 genes (pax7a1, pax7a2 and pax7b) in the rainbow trout genome. During in vitro myogenesis, pax7a1 transcripts remain stable, whereas pax7a2 and pax7b mRNAs increase in abundance, similarly to myogenin mRNAs but in contrast to the expression pattern of the mammalian ortholog. We also profile the distribution of repressive H3K27me3 and H3K9me3 and permissive H3K4me3 marks during in vitro myogenesis across these loci and find that pax7a2 expression is associated with decreased H3K27 trimethylation, whereas pax7b expression is correlated with decreased H3K9me3 and H3K27me3. These data link the unique differential expression of pax7 paralogs with epigenetic histone modifications in a vertebrate species displaying growth divergent from that of mammals and highlight an important divergence in the regulatory mechanisms of pax7 expression among vertebrates. The system described here provides a more comprehensive picture of the combinatorial control mechanisms orchestrating skeletal muscle growth in a salmonid, leading to a better understanding of myogenesis in this species and across Vertebrata more generally.
authors.affiliation: INRA, UR1067 Nutrition Métabolisme Aquaculture, F-64310, St-Pée-sur-Nivelle, France.
authors.forename: Iban
authors.initials: I
authors.lastname: Seiliez
authors.forename: Jacob Michael
authors.initials: JM
authors.lastname: Froehlich
authors.forename: Lucie
authors.initials: L
authors.lastname: Marandel
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Gabillard
authors.forename: Peggy R
authors.initials: PR
authors.lastname: Biga
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D049109:Cell Proliferation; D047369:Chromatin Immunoprecipitation; D044127:Epigenesis, Genetic; D019143:Evolution, Molecular; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D056426:Genetic Loci; D006657:Histones / Q000378:metabolism; D008745:Methylation; D024510:Muscle Development / Q000235:genetics; D017686:Oncorhynchus mykiss / Q000235:genetics*; D051763:PAX7 Transcription Factor / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D032496:Satellite Cells, Skeletal Muscle / Q000166:cytology / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D026801:Synteny / Q000235:genetics
chemical_list: D029941:Fish Proteins; D006657:Histones; D051763:PAX7 Transcription Factor; D012333:RNA, Messenger