title: Selective early expression of the orphan nuclear receptor Nr4a2 identifies the claustrum homolog in the avian mesopallium: Impact on sauropsidian/mammalian pallium comparisons.
abstract: The transcription factor Nr4a2 was recently revealed as a very early developmental marker of the claustrum (CL) proper in the mouse. The earliest claustral primordium was identified superficially, dorsal to the olfactory cortex, and was subsequently covered by the Nr4a2-negative cells of the insular cortex. Some tangentially migrating claustral derivatives (subplate cells and some endopiriform elements) also expressed this marker. The present study employs the same genetic marker to explore the presence of a comparable pallial division in chicken in which, in principle, the same pallial sectors exist as in mammals. We were indeed able to delineate an early-developing Nr4a2-positive mantle domain at the expected topologic position within the developing chicken lateral pallium. In the chicken as well as in the turtle (from data in the literature), the earliest postmitotic lateropallial cells likewise express Nr4a2 and occupy a corticoid superficial stratum of the mesopallium, which is clearly comparable in spatial and chronological profile to the mouse CL. Other cells produced in this pallial sector include various tangentially migrating Nr4a2-labeled derivatives as well as Nr4a2-negative and Nr4a2-positive local deeper subpopulations that partially interdigitate, forming mesopallial core and shell populations. We hold that the deep avian and reptilian mesopallial formation developing under the superficial corticoid CL homolog represents a field homolog of the insula, although additional studies are required to underpin this hypothesis.
authors.affiliation: Department of Human Anatomy, Faculty of Medicine, University of Murcia, and Instituto Murciano de Investigación Biosanitaria, Murcia, 30071, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Puelles
authors.affiliation: Department of Human Anatomy, Faculty of Medicine, University of Murcia, and Instituto Murciano de Investigación Biosanitaria, Murcia, 30071, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Ayad
authors.affiliation: Department of Human Anatomy, Faculty of Medicine, University of Murcia, and Instituto Murciano de Investigación Biosanitaria, Murcia, 30071, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Alonso
authors.affiliation: Department of Human Anatomy, Faculty of Medicine, University of Murcia, and Instituto Murciano de Investigación Biosanitaria, Murcia, 30071, Spain.
authors.forename: J E
authors.initials: JE
authors.lastname: Sandoval
authors.affiliation: Department of Human Anatomy, Faculty of Medicine, University of Murcia, and Instituto Murciano de Investigación Biosanitaria, Murcia, 30071, Spain.
authors.forename: M
authors.initials: M
authors.lastname: MartÍnez-de-la-Torre
authors.affiliation: Laboratory of Brain Development and Evolution, Department of Experimental Medicine, Faculty of Medicine, University of Lleida, and IRBLleida Institute of Biomedical Research of Lleida, Lleida, 25198, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Medina
authors.affiliation: Department of Human Anatomy, Faculty of Medicine, University of Murcia, and Instituto Murciano de Investigación Biosanitaria, Murcia, 30071, Spain.
authors.forename: J L
authors.initials: JL
authors.lastname: Ferran
mesh_terms: D000818:Animals; D030161:Avian Proteins / Q000378:metabolism*; D005075:Biological Evolution; D002642:Chick Embryo / Q000033:anatomy & histology* / Q000378:metabolism*; D017403:In Situ Hybridization; D051379:Mice; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2 / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013045:Species Specificity; D013687:Telencephalon / Q000033:anatomy & histology* / Q000196:embryology* / Q000378:metabolism; D014426:Turtles
chemical_list: D030161:Avian Proteins; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2
keywords: dorsal pallium; dorsal ventricular ridge; endopiriform nucleus; lateral pallium; olfactory cortex; pallial thickening; subplate; ventral pallium