Cajal-Retzius cell
Encyclopedia
The term Cajal–Retzius cell is applied to reelin
-producing neurons of the human embryonic marginal zone which display, as a salient feature, radial ascending processes that contact the pial surface
, and a horizontal axon plexus located in the deep marginal zone. These cells were first described by Retzius
(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 not only in the marginal zone of the human brain but in that of all amniote
s, which indicates their evolutionary homology
. However, mammal
ian Cajal–Retzius cells produce substantially higher amounts of reelin, pointing to the spatiotemporal control of reelin expression as a key feature of cortical evolution.
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 HAR1F
was the most "Human accelerated region
" of the genome. It was determined that the RNA product of the HAR1F
gene is expressed in Cajal–Retzius cells.
Chameau et al. (2009) report that Cajal–Retzius cells postnatally receive a major excitatory synaptic input via 5-HT3 receptor
s, and that abolishing this interaction deregulates cortical development, leading to an overgrowth of apical dendrites of layer 2\3 pyramidal cells.
Reelin
Reelin is a large secreted extracellular matrix protein that helps regulate processes of neuronal migration and positioning in the developing brain by controlling cell–cell interactions. Besides this important role in early development, reelin continues to work in the adult brain. It modulates the...
-producing neurons of the human embryonic marginal zone which display, as a salient feature, radial ascending processes that contact the pial surface
Pia mater
Pia mater often referred to as simply the pia, is the delicate innermost layer of the meninges, the membranes surrounding the brain and spinal cord. The word finds its roots in Latin, meaning literally "tender mother." The other two meningeal membranes are the dura mater and the arachnoid mater....
, and a horizontal axon plexus located in the deep marginal zone. These cells were first described by Retzius
Gustaf Retzius
Magnus 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 not only in the marginal zone of the human brain but in that of all amniote
Amniote
The amniotes are a group of tetrapods that have a terrestrially adapted egg. They include synapsids and sauropsids , 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...
s, which indicates their evolutionary homology
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...
. However, mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
ian Cajal–Retzius cells produce substantially higher amounts of reelin, pointing to the spatiotemporal control of reelin expression as a key feature of cortical evolution.
History
CajalSantiago Ramón y Cajal
Santiago Ramón y Cajal ForMemRS was a Spanish pathologist, histologist, neuroscientist, and Nobel laureate. His pioneering investigations of the microscopic structure of the brain were original: he is considered by many to be the father of modern neuroscience...
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 HAR1F
HAR1F
In molecular biology, Human accelerated region 1 is a segment of the human genome found on the long arm of chromosome 20. It is a Human accelerated region...
was the most "Human accelerated region
Human accelerated regions
Human 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 HAR1F
HAR1F
In molecular biology, Human accelerated region 1 is a segment of the human genome found on the long arm of chromosome 20. It is a Human accelerated region...
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 lissencephalyLissencephalyLissencephaly, 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...
; - EMX2EMX2Homeobox protein EMX2 is a protein that in humans is encoded by the EMX2 gene....
(Mallamaci et al., 1998); - FukutinFukutinFukutin is a eukaryotic protein necessary for the maintenance of muscle integrity, cortical histogenesis, and normal ocular development. Mutations in the fukutin gene have been shown to result in Fukuyama congenital muscular dystrophy characterised by brain malformation - one of the most common...
; - RELN (Meyer and Goffinet, 1998). The gene RELN encodes the protein reelinReelinReelin is a large secreted extracellular matrix protein that helps regulate processes of neuronal migration and positioning in the developing brain by controlling cell–cell interactions. Besides this important role in early development, reelin continues to work in the adult brain. It modulates the...
, which is secreted extracellularly by layer I neurones through a constitutive, nonvesicular mechanism (Lacor et al., 2000). This extracellular matrixExtracellular 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 reelerReelerA reeler is a mouse mutant, so named because of its characteristic "reeling" gait. This is caused by profound hypoplasia of the mouse's cerebellum, in which the normal cerebellar folia are missing. The mutation is autosomal and recessive....
mouse mutant, disturbance of the reelin signaling pathway or ablation of Cajal–Retzius cells causes disorders in cortical lamination. - HAR1FHAR1FIn molecular biology, Human accelerated region 1 is a segment of the human genome found on the long arm of chromosome 20. It is a Human accelerated region...
- P73P73p73 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 p53P53p53 , is a tumor suppressor protein that in humans is encoded by the TP53 gene. p53 is crucial 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 apoptosisApoptosisApoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
.
Chameau et al. (2009) report that Cajal–Retzius cells postnatally receive a major excitatory synaptic input via 5-HT3 receptor
5-HT3 receptor
The 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.
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 FrameworkNeuroscience Information FrameworkThe Neuroscience Information Framework is a repository of global neuroscience web resources, including experimental, clinical, and translational neuroscience databases, knowledge bases, atlases, and genetic/genomic resources.-Description:...