title: Origin of the cortical layer I in rodents.
abstract: Using birthdating techniques, we have studied when cells that settle in the marginal zone (future layer 1) of the cortical neuroepithelium are generated in developing rat embryos. The majority of marginal zone cells are generated at embryonic day 12 (E12), E13 and E14, although some cells generated later can incorporate into this stratum after the cortical plate forms. The nature and the origin of the cell populations that colonize the preplate/marginal zone was studied by means of immunohistochemistry using cell markers for gamma-amino butyric acid (GABA), reelin and the calcium binding proteins calretinin and calbindin. At early stages of development, the preplate is formed by Cajal-Retzius cells, subplate cells, subpial granular layer cells, some interneurons and some glial cells. With the arrival of the cortical plate cells, the subplate cells descend to occupy the stratum below. Layer 1 cells are of diverse origin as some of them are generated in the ventricular zone of the cortical neuroepithelium, whereas other cell populations come from extracortical regions such as the olfactory placode or the ganglionic eminences of the basal telencephalon. The predominant cell type in the marginal zone is the Cajal-Retzius cell, which expresses reelin and calretinin, and is probably generated in the cortical neuroepithelium. These cells can be readily distinguished from cells that come from the ganglionic eminences as these later populations mainly express GABA and calbindin. Finally, our results suggest that the cells of the subpial granular layer might be generated in the rostral pole of the lateral ganglionic eminences.
authors.affiliation: Instituto Cajal (CSIC), Madrid, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Jiménez
authors.forename: Rocío
authors.initials: R
authors.lastname: Rivera
authors.forename: Laura
authors.initials: L
authors.lastname: López-Mascaraque
authors.forename: Juan A
authors.initials: JA
authors.lastname: De Carlos
mesh_terms: D000818:Animals; D001973:Bromodeoxyuridine; D064032:Calbindin 2; D064026:Calbindins; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D019070:Cell Lineage / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D002540:Cerebral Cortex / Q000166:cytology* / Q000196:embryology*; D004622:Embryo, Mammalian; D005314:Embryonic and Fetal Development / Q000502:physiology*; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005260:Female; D007150:Immunohistochemistry; D008856:Microscopy, Fluorescence; D009419:Nerve Tissue Proteins; D009474:Neurons / Q000166:cytology*; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D000091042:Reelin Protein; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D012697:Serine Endopeptidases; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: C576512:Calb2 protein, rat; D064032:Calbindin 2; D064026:Calbindins; D015816:Cell Adhesion Molecules, Neuronal; D016326:Extracellular Matrix Proteins; D009419:Nerve Tissue Proteins; D000091042:Reelin Protein; C000717129:Reln protein, rat; D064030:S100 Calcium Binding Protein G; D005680:gamma-Aminobutyric Acid; D012697:Serine Endopeptidases; D001973:Bromodeoxyuridine