title: Divergent mechanisms regulate conserved cardiopharyngeal development and gene expression in distantly related ascidians.
abstract: Ascidians present a striking dichotomy between conserved phenotypes and divergent genomes: embryonic cell lineages and gene expression patterns are conserved between distantly related species. Much research has focused on Ciona or Halocynthia spp. but development in other ascidians remains poorly characterized. In this study, we surveyed the multipotent myogenic B7.5 lineage in Molgula spp. Comparisons to the homologous lineage in Ciona revealed identical cell division and fate specification events that result in segregation of larval, cardiac, and pharyngeal muscle progenitors. Moreover, the expression patterns of key regulators are conserved, but cross-species transgenic assays uncovered incompatibility, or 'unintelligibility', of orthologous cis-regulatory sequences between Molgula and Ciona. These sequences drive identical expression patterns that are not recapitulated in cross-species assays. We show that this unintelligibility is likely due to changes in both cis- and trans-acting elements, hinting at widespread and frequent turnover of regulatory mechanisms underlying otherwise conserved aspects of ascidian embryogenesis.
authors.affiliation: Center for Developmental Genetics, Department of Biology, New York University, New York, United States.
authors.forename: Alberto
authors.initials: A
authors.lastname: Stolfi
authors.affiliation: Department of Computer Science and Engineering, Michigan State University, East Lansing, United States.
authors.forename: Elijah K
authors.initials: EK
authors.lastname: Lowe
authors.affiliation: Cellular and Developmental Biology Laboratory, Stazione Zoologica Anton Dohrn, Napoli, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Racioppi
authors.affiliation: Cellular and Developmental Biology Laboratory, Stazione Zoologica Anton Dohrn, Napoli, Italy.
authors.forename: Filomena
authors.initials: F
authors.lastname: Ristoratore
authors.affiliation: Department of Computer Science and Engineering, Michigan State University, East Lansing, United States.
authors.forename: C Titus
authors.initials: CT
authors.lastname: Brown
authors.affiliation: Department of Biology, University of Washington, Seattle, United States.
authors.forename: Billie J
authors.initials: BJ
authors.lastname: Swalla
authors.affiliation: Center for Developmental Genetics, Department of Biology, New York University, New York, United States.
authors.forename: Lionel
authors.initials: L
authors.lastname: Christiaen
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000235:genetics; D019070:Cell Lineage / Q000235:genetics; D002465:Cell Movement / Q000235:genetics; D002938:Ciona intestinalis / Q000166:cytology / Q000196:embryology / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000166:cytology; D004789:Enzyme Activation; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D016678:Genome; D006321:Heart / Q000196:embryology*; D008648:Mesoderm / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009132:Muscles / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D010614:Pharynx / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D014561:Urochordata / Q000166:cytology / Q000196:embryology* / Q000235:genetics*
chemical_list: D020928:Mitogen-Activated Protein Kinases
keywords: DSD; ascidians; cardiopharyngeal mesoderm; development; developmental biology; evolution; evolutionary biology; genomics; stem cells; tunicates