The term
Cajal–Retzius cell is applied to
reelinReelin is a protein that helps regulate processes of neuronal migration and positioning in the developing brain. Besides this important role in early development, reelin continues to work in the adult brain. It modulates the synaptic plasticity by enhancing the induction and maintenance of...
-producing neurons of the human embryonic marginal zone which display, as a salient feature, radial ascending processes that contact the
pial surfaceThe pia mater is the delicate innermost layer of the meninges—the membranes surrounding the brain and spinal cord....
, and a horizontal axon plexus located in the deep marginal zone. These cells were first described by
RetziusMagnus Gustaf Retzius was a Swedish physician and anatomist who dedicated a large part of his life to researching the histology of the sense organs and nervous system.-Biography:...
(Retzius, 1893, 1894).
Cajal–Retzius cells possess very long horizontal axons that form asymmetric synaptic contacts with dendritic shafts or spines of neocortical pyramidal cells.
The term
Cajal–Retzius cell is applied to
reelinReelin is a protein that helps regulate processes of neuronal migration and positioning in the developing brain. Besides this important role in early development, reelin continues to work in the adult brain. It modulates the synaptic plasticity by enhancing the induction and maintenance of...
-producing neurons of the human embryonic marginal zone which display, as a salient feature, radial ascending processes that contact the
pial surfaceThe pia mater is the delicate innermost layer of the meninges—the membranes surrounding the brain and spinal cord....
, and a horizontal axon plexus located in the deep marginal zone. These cells were first described by
RetziusMagnus Gustaf Retzius was a Swedish physician and anatomist who dedicated a large part of his life to researching the histology of the sense organs and nervous system.-Biography:...
(Retzius, 1893, 1894).
Cajal–Retzius cells possess very long horizontal axons that form asymmetric synaptic contacts with dendritic shafts or spines of neocortical pyramidal cells. Although their exact origin remains a subject of controversy, the caudomedial wall of the telencephalic vesicle has been proposed as the primary source.
Cajal–Retzius cells are found in the marginal zone in all
amnioteThe amniotes are a group of tetrapod vertebrates that have a terrestrially adapted egg. They include mammals, birds and reptiles, as well as their fossil ancestors. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes. In humans,...
s, which indicates their evolutionary
homologyIn evolutionary biology, homology refers to any similarity between characteristics of organisms that is due to their shared ancestry. The word homologous derives from the ancient Greek ομολογειν, 'to agree'. There are examples in different branches of biology...
. However,
mammalMammals are a class of vertebrate animals whose females are characterized by the possession of mammary glands while both males and females are characterized by sweat glands, hair, three middle ear bones used in hearing, and a neocortex region in the brain.Mammals are divided into three main...
ian Cajal–Retzius cells produce substantially higher amounts of
reelinReelin is a protein that helps regulate processes of neuronal migration and positioning in the developing brain. Besides this important role in early development, reelin continues to work in the adult brain. It modulates the synaptic plasticity by enhancing the induction and maintenance of...
, pointing to the spatiotemporal control of reelin expression as a key feature of cortical evolution.
History
CajalSantiago Ramón y Cajal was a Spanish histologist, physician, pathologist and Nobel laureate. His pioneering investigations of the microscopic structure of the brain were so original and influential that he is considered by many to be the greatest neuroscientist of all time...
described in 1891 slender horizontal bipolar cells in the developing marginal zone of lagomorphs.
(See the Cajal's original drawing of the cells) These cells were considered by Retzius as homologues to the cells he found in humans and in other mammals (Retzius, 1893, 1894). Similar cells are also present in the rodent marginal zone.
In 2006 a comparison of human and chimpanzees DNA determined that the gene designated
HAR1FHAR1F is a RNA gene which is part of a human accelerated region of the human genome. HAR1F is found on the long arm of chromosome 20 and the RNA product is expressed in Cajal-Retzius cells, where it colocalizes with the protein reelin....
was the most "
Human accelerated regionHuman accelerated regions , first described in August 2006, are a set of 49 segments of the human genome which are conserved throughout vertebrate evolution but are strikingly different in humans. They are named HAR1 through HAR49 according to their degree of difference between humans and chimpanzees...
" of the genome. It was determined that the RNA product of the
HAR1FHAR1F is a RNA gene which is part of a human accelerated region of the human genome. HAR1F is found on the long arm of chromosome 20 and the RNA product is expressed in Cajal-Retzius cells, where it colocalizes with the protein reelin....
gene is expressed in Cajal-Retzius cells.
Role in the cortex
CR cells establish early neuronal circuitry in the developing brain (Aguiló et al., 1999), and express a number of genes known to be important in human cerebral development:
- LIS1 (Clark et al., 1997), which is mutated in lissencephaly
Lissencephaly, which literally means smooth brain, is a rare brain formation disorder caused by defective neuronal migration during the 12th to 24th weeks of gestation, resulting in a lack of development of brain folds and grooves . It is a form of cephalic disorder...
;
- EMX2 (Mallamaci et al., 1998);
- Fukutin
Fukutin is a protein associated with Fukuyama congenital muscular dystrophy.It has also been associated with dilated cardiomyopathy....
;
- RELN (Meyer and Goffinet, 1998). The gene RELN encodes the protein reelin
Reelin is a protein that helps regulate processes of neuronal migration and positioning in the developing brain. Besides this important role in early development, reelin continues to work in the adult brain. It modulates the synaptic plasticity by enhancing the induction and maintenance of...
, which is secreted extracellularly by layer I neurones through a constitutive, nonvesicular mechanism (Lacor et al., 2000). This extracellular matrixIn biology, the extracellular matrix is the extracellular part of animal tissue that usually provides structural support to the animal cells in addition to performing various other important functions. The extracellular matrix is the defining feature of connective tissue in animals.Extracellular...
protein, which is also secreted by Cajal–Retzius neurons, serves as a signal to dissociate for migrating neurons, which travel in clusters, and controls the formation of cortical layers. Lack of reelin, as in the reelerThe reeler is an autosomal recessive mouse mutant, in which cortical neurons are generated normally but are abnormally placed, resulting in disorganization of cortical laminar layers in the CNS...
mouse mutant, disturbance of the reelin signaling pathway or ablation of Cajal–Retzius cells causes disorders in cortical lamination.
- HAR1F
HAR1F is a RNA gene which is part of a human accelerated region of the human genome. HAR1F is found on the long arm of chromosome 20 and the RNA product is expressed in Cajal-Retzius cells, where it colocalizes with the protein reelin....
- P73
p73 is a protein related to the p53 tumor protein. Because of its structural resemblance to p53, it has also been considered a tumor suppressor. It is involved in cell cycle regulation, and induction of apoptosis. Like p53, p73 is characterized by the presence of different isoforms of the protein...
protein, a p53p53 , is a transcription factor which in humans is encoded by the TP53 gene. p53 is important in multicellular organisms, where it regulates the cell cycle and thus functions as a tumor suppressor that is involved in preventing cancer...
-family member involved in the processes of cell survival and apoptosisApoptosis is the process of programmed cell death that may occur in multicellular organisms. Programmed cell death involves a series of biochemical events leading to a characteristic cell morphology and death; in more specific terms, a series of biochemical events that lead to a variety of...
.
Chameau et al. (2009) report that Cajal–Retzius cells postnatally receive a major excitatory synaptic input via
5-HT3 receptorThe 5-HT3 receptor is a member of the superfamily of ligand-gated ion channels, a superfamily that also includes the neuronal nicotinic acetylcholine receptors , and the inhibitory neurotransmitter receptors for GABA and glycine...
s, and that abolishing this interaction deregulates cortical development, leading to an overgrowth of apical dendrites of layer 2\3 pyramidal cells.
Sources
- Retzius G (1893) Die Cajal'schen Zellen der Grosshirnrinde beim Menschen und bei Säugetieren. Biologische Untersuchungen, Neue Folge 5:1–8.
- Retzius G (1894) Weitere Beiträge zur Kenntniss der Cajal'schen Zellen der Grosshirnrinde des Menschen. Biologische Untersuchungen. Neue Folge 6:29–36.
- Meyer G, Goffinet AM, Fairen A. (1999) What is a Cajal–Retzius cell? A reassessment of a classical cell type based on recent observations in the developing neocortex. Cereb Cortex. 9(8):765-75. PMID 10600995
External links
- Feature Article: What is a Cajal–Retzius cell? A Reassessment of a Classical Cell Type Based on Recent Observations in the Developing Neocortex - Cerebral Cortex, Vol. 9, No. 8, 765-775, December 1999
- Active Networks in the Early Brain - "Editors' Choice: Highlights of the recent literature" in the journal Science, 13 September 2002, Vol. 297. no. 5588, p. 1773
- NIF Search - Cajal-Retzius Cell via the Neuroscience Information Framework
The Neuroscience Information Framework is a repertory of global neuroscience web resources, including experimental, clinical, and translational neuroscience databases, knowledge bases, atlases, and genetic/genomic resources.- Description :...