title: Recurrent DCC gene losses during bird evolution.
abstract: During development, midline crossing by axons brings into play highly conserved families of receptors and ligands. The interaction between the secreted ligand Netrin-1 and its receptor Deleted in Colorectal Carcinoma (DCC) is thought to control midline attraction of crossing axons. Here, we studied the evolution of this ligand/receptor couple in birds taking advantage of a wealth of newly sequenced genomes. From phylogeny and synteny analyses we can infer that the DCC gene has been conserved in most extant bird species, while two independent events have led to its loss in two avian groups, passeriformes and galliformes. These convergent accidental gene loss events are likely related to chromosome Z rearrangement. We show, using whole-mount immunostaining and 3Disco clearing, that in the nervous system of all birds that have a DCC gene, DCC protein expression pattern is similar to other vertebrates. Surprisingly, we show that the early developmental pattern of commissural tracts is comparable in all birds, whether or not they have a DCC receptor. Interestingly, only 4 of the 5 genes encoding secreted netrins, the DCC ligands in vertebrates, were found in birds, but Netrin-5 was absent. Together, these results support a remarkable plasticity of commissural axon guidance mechanisms in birds.
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 Rue Moreau, 75012 Paris, France.
authors.forename: François
authors.initials: F
authors.lastname: Friocourt
authors.affiliation: Muséum National d'Histoire Naturelle, Sorbonne Universités, Research Unit BOREA, Biology of Aquatic Organisms and Ecosystems, CNRS 7208, IRD207, UPMC, UCN, Paris, France.
authors.forename: Anne-Gaelle
authors.initials: AG
authors.lastname: Lafont
authors.affiliation: Université Lyon 1, INSERM, INRA, Stem Cell and Brain Research Institute, U1208, USC1361, 69500 Bron, France.
authors.forename: Clémence
authors.initials: C
authors.lastname: Kress
authors.affiliation: Université Lyon 1, INSERM, INRA, Stem Cell and Brain Research Institute, U1208, USC1361, 69500 Bron, France.
authors.forename: Bertrand
authors.initials: B
authors.lastname: Pain
authors.affiliation: Center for Interdisciplinary Research in Biology, CNRS UMR 7241, Collège de France, 75005 Paris, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Manceau
authors.affiliation: Muséum National d'Histoire Naturelle, Sorbonne Universités, Research Unit BOREA, Biology of Aquatic Organisms and Ecosystems, CNRS 7208, IRD207, UPMC, UCN, Paris, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Dufour
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 Rue Moreau, 75012 Paris, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Chédotal
mesh_terms: D000818:Animals; D030161:Avian Proteins / Q000235:genetics* / Q000378:metabolism; D000071437:Axon Guidance; D001369:Axons / Q000502:physiology*; D005075:Biological Evolution; D001717:Birds; D001921:Brain / Q000502:physiology*; D017124:Conserved Sequence; D000075389:DCC Receptor / Q000235:genetics* / Q000378:metabolism; D000075388:Netrin-1 / Q000378:metabolism*; D009473:Neuronal Plasticity; D009474:Neurons / Q000502:physiology*; D010802:Phylogeny; D017384:Sequence Deletion / Q000235:genetics*; D014714:Vertebrates
chemical_list: D030161:Avian Proteins; D000075389:DCC Receptor; D000075388:Netrin-1