title: Appendage expression driven by the Hoxd Global Control Region is an ancient gnathostome feature.
abstract: The evolutionary transition of the fins of fish into tetrapod limbs involved genetic changes to developmental systems that resulted in novel skeletal patterns and functions. Approaches to understanding this issue have entailed the search for antecedents of limb structure in fossils, genes, and embryos. Comparative genetic analyses have produced ambiguous results: although studies of posterior Hox genes from homology group 13 (Hoxa-13 and Hoxd-13) reveal similarities in gene expression between the distal segments of fins and limbs, this functional homology has not been supported by genomic comparisons of the activity of their cis-regulatory elements, namely the Hoxd Global Control Region. Here, we show that cis-regulatory elements driving Hoxd gene expression in distal limbs are present in fish. Using an interspecies transgenesis approach, we find functional conservation between gnathostome Hoxd enhancers, demonstrating that orthologous sequences from tetrapods, zebrafish and skate can drive reporter gene expression in mouse limbs and zebrafish fins. Our results support the notion that some of the novelties associated with tetrapod limbs arose by modification of deeply conserved cis- and trans-acting mechanisms of Hox regulation in gnathostomes.
authors.affiliation: Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Igor
authors.initials: I
authors.lastname: Schneider
authors.forename: Ivy
authors.initials: I
authors.lastname: Aneas
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Gehrke
authors.forename: Randall D
authors.initials: RD
authors.lastname: Dahn
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Nobrega
authors.forename: Neil H
authors.initials: NH
authors.lastname: Shubin
mesh_terms: D058500:Animal Fins / Q000033:anatomy & histology / Q000196:embryology / Q000378:metabolism; D000818:Animals; D030801:Animals, Genetically Modified; D005075:Biological Evolution; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism; D004622:Embryo, Mammalian / Q000196:embryology / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000196:embryology / Q000378:metabolism; D005121:Extremities / Q000033:anatomy & histology / Q000196:embryology; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D018398:Homeodomain Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D010802:Phylogeny; D000075223:Poly-ADP-Ribose Binding Proteins; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D012860:Skates, Fish / Q000196:embryology / Q000235:genetics; D014157:Transcription Factors / Q000145:classification / Q000235:genetics / Q000378:metabolism; D014714:Vertebrates / Q000145:classification / Q000196:embryology / Q000235:genetics*; D015027:Zebrafish / Q000196:embryology / Q000235:genetics
chemical_list: D018398:Homeodomain Proteins; C084118:Hoxd13 protein, mouse; D000075223:Poly-ADP-Ribose Binding Proteins; D014157:Transcription Factors; C099959:homeobox protein HOXA13; D049452:Green Fluorescent Proteins; D004265:DNA Helicases; C078673:ERCC6 protein, human; D045643:DNA Repair Enzymes