Cajal-Retzius cell

[
Santiago Ramón y Cajal in 1891]

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. Takiguchi-Hayashi K, Sekiguchi M, Ashigaki S, Takamatsu M, Hasegawa H, Suzuki-Migishima R, Yokoyama M, Nakanishi S, Tanabe Y. (2004) "Generation of reelin-positive marginal zone cells from the caudomedial wall of telencephalic vesicles." J Neurosci. 24(9):2286-95. PMID 14999079 ( [http://www.jneurosci.org/cgi/content/full/24/9/2286 free full text] )]

Cajal–Retzius cells are found in the marginal zone in all amniotes, which indicates their evolutionary homology. However, mammalian Cajal–Retzius cells produce substantially higher amounts of reelin, pointing to the spatiotemporal control of reelin expression as a key feature of cortical evolution. Bar I, Lambert de Rouvroit C, Goffinet AM. (2000) "The evolution of cortical development. An hypothesis based on the role of the Reelin signaling pathway." Trends Neurosci. 23(12):633-8. PMID 11137154 ]

History

Cajal described in 1891 slender horizontal bipolar cells in the developing marginal zone of lagomorphs. [http://cercor.oxfordjournals.org/cgi/content/full/9/8/765/F2 (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.

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;
* EMX2 (Mallamaci et al., 1998);
* Fukutin; cite journal |author=Saito Y, Mizuguchi M, Oka A, Takashima S |title=Fukutin protein is expressed in neurons of the normal developing human brain but is reduced in Fukuyama-type congenital muscular dystrophy brain |journal=Ann. Neurol. |volume=47 |issue=6 |pages=756–64 |year=2000 |pmid=10852541 |doi=]
* RELN (Meyer and Goffinet, 1998). The gene RELN encodes the protein reelin, which is secreted extracellularly by layer I neurones through a constitutive, nonvesicular mechanism (Lacor et al., 2000). This extracellular matrix 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 reeler mouse mutant, disturbance of the reelin signaling pathway or ablation of Cajal-Retzius cells causes disorders in cortical lamination.
*HAR1F
*P73 protein, a p53-family member involved in the processes of cell survival and apoptosis. Meyer G, Cabrera Socorro A, Perez Garcia CG, Martinez Millan L, Walker N, Caput D. (2004) "Developmental roles of p73 in Cajal-Retzius cells and cortical patterning."J Neurosci.24(44):9878-87.PMID 15525772]

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

References

External links

* [http://cercor.oxfordjournals.org/cgi/content/full/9/8/765 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

* [http://www.sciencemag.org/cgi/content/short/297/5588/1773a 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