Details for: CL0000695

Cell ID: CL0000695

Cell Name: Cajal-Retzius cell

Description: A type of transient, early-born glutamatergic neuron located primarily in the marginal zone (future layer I) of the developing cerebral cortex and hippocampus in vertebrates. it is characterized by a bipolar morphology with an elongated soma, a single thick dendrite oriented toward the pial surface, and a long, thin axon that extends tangentially to form horizontal plexuses across the cortical surface. It is important for the multiple developmental processes including migration, dendritogenesis and synaptogenesis. It typically undergoes programmed cell death following cortical maturation with species- and region specific patterns of survival. In mice, it is predominantly observed in the hippocampal formation, particularly in the stratum lacunosum-moleculare and outer molecular layer of the dentate gyrus (van Bruggen et al., 2023). In contrast, in humans, a second morphologically distinct subpopulation emerges mid-gestation and persists postnatally, with surviving cells observed in the cortical sulci and the hippocampus.

Synonyms: CR cells, Horizontal cells of Cajal

Selected Context(s): Overall

Gene Significance Landscape

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Cell Significance Index (CSI) is uniquely calculated to reveal cell-specific gene markers. More info here

Significant Genes List

Genes with the highest and lowest Percentile Rank Scores (PRS) for Cajal-Retzius cell within the selected context(s).

Gene ID: A unique numerical identifier for this specific gene.
Symbol: Shortened abbreviation or name that represents this gene.
Ensembl Gene ID: A unique identifier assigned by Ensembl for genomic data mapping.
CSI Score: A combined effect size and statistical significance measure for Cajal-Retzius cell. Higher scores indicate a stronger, more significant difference in expression.
(Previously described as "Fold Change", but now represents Cliff's Delta × –log10(p).)

Gene ID: A unique numerical identifier for this specific gene.
Symbol: Shortened abbreviation or name that represents this gene.
Ensembl Gene ID: A unique identifier assigned by Ensembl for genomic data mapping.
CSI Score: A combined effect size and statistical significance measure for Cajal-Retzius cell. Higher scores indicate a stronger, more significant difference in expression.
Average CSI: csi sum / gene count
Cell network configuration

This network visualizes key genes for Cajal-Retzius cell. It primarily includes:
1. Top genes highly significant for this cell (Num. Top Cell Genes - based on the 'Min. CSI' setting).
2. Any additional specific 'Context Genes' you add below.
The final network is a combined view. Choose an Interaction Source (pathways or protein interactions) and optionally compare CSI scores with a Baseline Cell Type.

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Target Cell for CSI:  Cajal-Retzius cell (CL0000695)

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Node size also reflects Target Cell CSI magnitude.
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Edges (Interactions):
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## Summary The [Cajal-Retzius cell](/details-cell/CL0000695) is a transient, glutamatergic neuron critical for the development and organization of the cerebral cortex. It resides in the marginal zone of the developing cortex, where it orchestrates neuronal migration and synaptogenesis. Based on gene significance analysis, the **Overall** defining characteristic of this cell is an exceptionally specific and pronounced expression of genes related to mitochondrial respiration and energy metabolism. This suggests that a highly specialized and robust metabolic program is fundamental to its unique identity and function in guiding cortical lamination, distinguishing it from other cell types primarily through its bioenergetic capacity rather than its neurotransmitter profile alone. ## Key Characteristics and Function The molecular profile of the [Cajal-Retzius cell](/details-cell/CL0000695) underscores its role as a highly active, post-mitotic neuron with a unique metabolic specialization. The top marker genes can be organized into several key functional clusters. * **Mitochondrial Respiration and Energy Metabolism:** The most striking feature is the high specificity (CSI Z-Score) of numerous genes encoding components of the electron transport chain and ATP synthesis. This includes [NDUFA4](/details-gene/4697) (CSI: 13.60), multiple cytochrome c oxidase subunits like [COX4I1](/details-gene/1327), [COX6A1](/details-gene/1337), [COX7A2](/details-gene/1347), [COX5B](/details-gene/1329), and [COX6C](/details-gene/1345), as well as ATP synthase components such as [ATP5PF](/details-gene/522) and [ATP5F1E](/details-gene/514). The high significance of genes involved in glycolysis ([GAPDH](/details-gene/2597)) and lactate metabolism ([LDHB](/details-gene/3945)) further supports the notion of a highly active and specialized metabolic state. This intense bioenergetic activity is likely required to fuel the cell's extensive tangential axonal growth and the synthesis of signaling molecules crucial for cortical development. The high specificity of the antioxidant enzyme [SOD1](/details-gene/6647) also suggests a dedicated mechanism to manage the oxidative stress resulting from this high metabolic rate. * **Neuronal Structure and Axon Guidance:** The cell's identity as a neuron is supported by the specific expression of [STMN2](/details-gene/11075), a neuron-specific growth-associated protein. Furthermore, the high significance of [CFL1](/details-gene/1072), a key regulator of actin dynamics, points to its role in maintaining cytoskeletal integrity and motility required for its morphology and function. Intriguingly, [RTN4](/details-gene/57142) (Nogo), a well-known inhibitor of neurite outgrowth in the mature central nervous system, is also a highly specific marker. This suggests a potential role in refining its own axonal pathways, confining them to the marginal zone, or providing repulsive cues to migrating neurons. * **Protein Homeostasis and Calcium Signaling:** The high specificity of [SKP1](/details-gene/6500), an essential component of ubiquitin ligase complexes, indicates robust control over protein turnover. Additionally, the specific expression of two calmodulin genes, [CALM2](/details-gene/805) and [CALM1](/details-gene/801), highlights the importance of calcium signaling pathways, which are central to neuronal activity, neurotransmitter release, and developmental processes. * **Negative Profile:** The anti-marker list confirms the cell's identity. The low significance of various transcription factors like [JUN](/details-gene/3725) and [KLF6](/details-gene/1316), and cell cycle regulators like [RPRM](/details-gene/56475), is consistent with a terminally differentiated, post-mitotic state. The negative CSI for [B2M](/details-gene/567), a component of the MHC class I complex, strongly suggests that these cells have low immunogenicity and are not primary targets for T-cell surveillance, befitting their crucial role in the immunoprivileged developing brain. ## Clinical Significance and Contextual Roles **Overall**, the gene signature of the [Cajal-Retzius cell](/details-cell/CL0000695) points to its potential vulnerability in neurodevelopmental disorders. Its profound reliance on a specific mitochondrial and metabolic program suggests that genetic or environmental factors disrupting cellular energy production during gestation could disproportionately affect Cajal-Retzius cell function or survival, leading to cascading defects in cortical layer formation. The high specificity of [SOD1](/details-gene/6647), an enzyme whose mutations are famously linked to amyotrophic lateral sclerosis (ALS), indicates that managing oxidative stress is a key feature of this cell. While its role here is developmental, this finding underscores the general importance of antioxidant defenses in specialized neurons. Similarly, the specific expression of [RTN4](/details-gene/57142) is clinically significant; while typically studied in the context of inhibiting regeneration after CNS injury, its prominent role in this key developmental neuron suggests its functions are highly context-dependent and crucial for establishing proper neural circuits from the outset. ## Potential Mechanisms and Research Directions 1. **Hypothesis:** The defining functional characteristic of Cajal-Retzius cells is a highly specialized metabolic program, marked by the specific expression of numerous mitochondrial genes. This unique bioenergetic state is not merely for housekeeping but is a primary driver of their core developmental functions, including the synthesis and secretion of guidance cues (e.g., Reelin) and the maintenance of their extensive, tangentially-oriented axon plexuses that span the developing cortex. * **Surprising Findings:** The most specific molecular identifiers for this critical neurodevelopmental cell are not classic guidance receptors or transcription factors, but rather core components of the electron transport chain ([NDUFA4](/details-gene/4697), [COX4I1](/details-gene/1327)). This suggests that metabolic phenotype, rather than signaling identity, may be the most unique feature distinguishing this cell from its neighbors during development. * **Testable Questions:** Does selective inhibition of key mitochondrial respiratory chain components, such as NDUFA4, in developing cortical organoids or in vivo mouse models lead to specific defects in Cajal-Retzius cell morphology, Reelin secretion, and subsequent neuronal migration, thereby phenocopying known corticogenesis disorders? 2. **Hypothesis:** The specific expression of the neurite outgrowth inhibitor [RTN4](/details-gene/57142) (Nogo) in Cajal-Retzius cells serves a non-canonical, constructive role in cortical lamination. Instead of being broadly inhibitory, it may function to precisely constrain the cell's own axons to the marginal zone (layer I) or act as a short-range repulsive signal that helps "corral" migrating neurons into their correct positions just below this layer. * **Surprising Findings:** A molecule best known for preventing axon regeneration in the mature, injured brain ([RTN4](/details-gene/57142)) is a highly specific marker of a cell type that is instrumental in building the brain's architecture. This paradoxical expression suggests a fundamental, context-dependent repurposing of its molecular function during development. * **Testable Questions:** What is the effect of a conditional knockout of [RTN4](/details-gene/57142) specifically within Cajal-Retzius cells on their axonal morphology, the integrity of the marginal zone axon plexus, and the final laminar positioning of projection neurons in the developing cortex?