title: Novel calretinin and reelin expressing neuronal population includes Cajal-Retzius-type cells in the neocortex of adult pigs.
abstract: Cajal-Retzius cells and their secreted product reelin are essential for the lamination of the cerebral cortex. In all species studied to date Cajal-Retzius cells form a transient neuronal population that almost completely disappears from the neocortex postnatally. Recently, in the hippocampal formation of adult domestic pig, we have found a large calretinin- and reelin-immunoreactive cell population that morphologically corresponded to Cajal-Retzius cells. In the present study, we examined calretinin- and reelin-immunoreactive neurons in layer I of the prefrontal, temporal, parietal and occipital neocortical areas of newborn, young adult and adult domestic pigs. Large numbers of bipolar or fusiform calretinin-positive cells were found in the upper half of layer I in all examined age groups. The morphology of these neurons resembled that of the Cajal-Retzius cells. Layer I was occupied by a dense calretinin-positive axonal plexus that was similar to the previously described axons of Cajal-Retzius cells in other species. In a similar location, where calretinin-positive cells occurred in layer I, large numbers of reelin-immunoreactive cells were found in all examined age groups. In addition, reelin colocalized with calretinin in layer I neurons. The number of calretinin and reelin-positive neurons decreased from 1 day to one year, but calretinin-positive Cajal-Retzius-type cells still comprised a remarkable large population in 12-month-old animals. Correlated light and electron microscopic examination of calretinin-labeled Cajal-Retzius-type cells indicated that these cells are integrated in the synaptic circuitry of the neocortex. Our results suggest that Cajal-Retzius cells do not disappear inevitably from the mature neocortex in all mammalian species. The function of this cell type is not known, but late persisting Cajal-Retzius-type cells in the domestic pig provide an opportunity to study their neuronal connections and the possible role of reelin in plasticity and regeneration of neocortex.
authors.affiliation: Central Electron Microscopic Laboratory, Faculty of Medicine, University of Pécs, 7643 Pécs, Szigeti u. 12, P.O. Box 99, Hungary.
authors.forename: H
authors.initials: H
authors.lastname: Abrahám
authors.forename: Z
authors.initials: Z
authors.lastname: Tóth
authors.forename: F
authors.initials: F
authors.lastname: Bari
authors.forename: F
authors.initials: F
authors.lastname: Domoki
authors.forename: L
authors.initials: L
authors.lastname: Seress
mesh_terms: D000375:Aging / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D064032:Calbindin 2; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D016253:Microscopy, Immunoelectron; D019579:Neocortex / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure; D009778:Occipital Lobe / Q000378:metabolism; D010296:Parietal Lobe / Q000378:metabolism; D017397:Prefrontal Cortex / Q000378:metabolism; D000091042:Reelin Protein; D064030:S100 Calcium Binding Protein G / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000378:metabolism*; D013552:Swine; D014018:Tissue Distribution
chemical_list: D064032:Calbindin 2; D015816:Cell Adhesion Molecules, Neuronal; D016326:Extracellular Matrix Proteins; D009419:Nerve Tissue Proteins; D000091042:Reelin Protein; D064030:S100 Calcium Binding Protein G; D012697:Serine Endopeptidases