title: Tangentially migrating GABAergic cells of subpallial origin invade massively the pallium in developing sharks.
abstract: We studied the development of the GABAergic system in the telencephalon of the dogfish Scyliorhinus canicula using GABA and glutamate decarboxylase (GAD) immunocytochemistry. The earliest GABA-expressing cells appeared in the basal telencephalon (subpallium) of stage 24 embryos. Shortly after, the subpallium showed abundant GABA-expressing neuroblasts near the meningeal surface or migrating radially in the neuroepithelium. The limit between the GABA-expressing region and the remainder of the telencephalon (pallium) was sharp and coincides with the pallial/subpallial boundary. At stage 28, GABA-expressing cells with the morphology of tangentially migrating cells (showing a thick growth cone-like leading process) migrate from a dome-shaped protrusion of the lateral subpallium and extended laterally and rostrodorsally into the pallium following either a superficial route or coursing periventricularly. At later stages, abundant GABA-expressing cells were seen in various pallial regions and strings of GABA-expressing cells, possibly migrating, were also noted. The colonization of the dogfish pallium by GABA-expressing cells, originating from the subpallium, is strongly reminiscent of the palliopetal tangential migrations of GABA-expressing cells demonstrated in the telencephalon of mammals and follows similar routes. These results strongly suggest that tangential migrations of GABA-expressing cells appeared very early in vertebrate forebrain evolution.
authors.affiliation: Department of Cell Biology and Ecology, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain.
authors.forename: Iván
authors.initials: I
authors.lastname: Carrera
authors.forename: Susana
authors.initials: S
authors.lastname: Ferreiro-Galve
authors.forename: Catalina
authors.initials: C
authors.lastname: Sueiro
authors.forename: Ramón
authors.initials: R
authors.lastname: Anadón
authors.forename: Isabel
authors.initials: I
authors.lastname: Rodríguez-Moldes
mesh_terms: D000818:Animals; D004625:Embryo, Nonmammalian; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D005968:Glutamate Decarboxylase / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D012754:Sharks / Q000033:anatomy & histology* / Q000196:embryology / Q000378:metabolism*; D013687:Telencephalon / Q000166:cytology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase