Expression of the Emx-1 and Dlx-1 homeobox genes define three molecularly distinct domains in the telencephalon of mouse, chick, turtle and frog embryos: implications for the evolution of telencephalic subdivisions in amniotes.
Homologies between vertebrate forebrain subdivisions are still uncertain. In particular the identification of homologs of the mammalian neocortex or the dorsal ventricular ridge (DVR) of birds and reptiles is still a matter of dispute. To get insight about the organization of the primordia of the main telencephalic subdivisions along the anteroposterior axis of the neural tube, a fate map of the dorsal prosencephalon was obtained in avian chimeras at the 8- to 9-somite stage. At this stage, the primordia of the pallium, DVR and striatum were located on the dorsal aspect of the prosencephalon and ordered caudorostrally along the longitudinal axis of the brain. Expression of homeobox-containing genes of the Emx, Dlx and Pax families were used as markers of anteroposterior developmental subdivisions of the forebrain in mouse, chick, turtle and frog. Their expression domains delineated three main telencephalic subdivisions in all species at the onset of neurogenesis: the pallial, intermediate and striatal neuroepithelial domains. The fate of the intermediate subdivisions diverged, however, between species at later stages of development. Homologies between forebrain subdivisions are proposed based on the conservation and divergence of these gene expression patterns.
Fernandez
A S
AS
CNRS URA 1414, Equipe Régionalisation Nerveuse, Ecole Normale Supérieure, 46, rue d'Ulm 75230 PARIS Cedex 05 France.
Pieau
C
C
Repérant
J
J
Boncinelli
E
E
Wassef
M
M
D000818:Animals; D002642:Chick Embryo; D003001:Cloning, Molecular; D003370:Coturnix; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D005136:Eye Proteins; D015870:Gene Expression; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008954:Models, Biological; D009687:Nuclear Proteins / Q000096:biosynthesis; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D013687:Telencephalon / Q000196:embryology*; D013997:Time Factors; D014018:Tissue Distribution; D016378:Tissue Transplantation; D014157:Transcription Factors; D014426:Turtles; D014714:Vertebrates / Q000196:embryology; D014982:Xenopus laevis; D000099260:Empty Spiracles Homeobox Proteins
D004268:DNA-Binding Proteins; D005136:Eye Proteins; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins; D014157:Transcription Factors; D000099260:Empty Spiracles Homeobox Proteins; C088334:Distal-less homeobox proteins; C000605732:Pax6 protein, mouse