Details for: CL0002306

Cell ID: CL0002306

Cell Name: epithelial cell of proximal tubule

Description: The vast majority of proximal tubule epithelial cells have a brush border, but there are rare exceptions.

Synonyms: kidney proximal tubule epithelial cell

Selected Context(s): Overall

Gene Significance Landscape

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Score:
Display
Genes

Contexts:

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

Image representation

Depiction of epithelial cell of proximal tubule
Courtesy of SwissBioPics

Significant Genes List

Genes with the highest and lowest Percentile Rank Scores (PRS) for epithelial cell of proximal tubule 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 epithelial cell of proximal tubule. 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 epithelial cell of proximal tubule. 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 epithelial cell of proximal tubule. 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.

Maximum number of selected genes.
Select a context for the baseline cell.
Select a context for the target cell.
Target Cell for CSI:  epithelial cell of proximal tubule (CL0002306)

 Legend
Nodes (Genes):
 Query Gene
Node size also reflects Target Cell CSI magnitude.
Node Color (Target Cell CSI in specific network):
 Very High
 High
 Medium
 Low
 Very Low
 N/A or Not Sig.
Edges (Interactions):
 STRING (Protein-Protein)
 ONTOLOGY (Shared Pathway)
 Colors vary by pathway category; default arrow applies.

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## Summary The [epithelial cell of proximal tubule](/details-cell/CL0002306) is a highly specialized cell type lining the proximal tubules of the kidney, characterized by a dense apical brush border that facilitates its primary function of reabsorption. **Overall**, the gene significance profile of this cell is overwhelmingly dominated by the specific and abundant expression of genes encoding components of the mitochondrial electron transport chain and ATP synthase complex. This molecular signature strongly underscores its role as a metabolically hyperactive cell, with an immense capacity for aerobic respiration to fuel the extensive active transport required for reclaiming the majority of solutes and water from the glomerular filtrate. ## Key Characteristics and Function The defining characteristic of the [epithelial cell of proximal tubule](/details-cell/CL0002306) is its exceptionally high metabolic rate, a feature reflected in its top marker genes. * **Mitochondrial Bioenergetics:** A large cluster of genes encoded by the mitochondrial genome exhibits profoundly high specificity, as indicated by their top-tier Z-score CSI values. These include multiple subunits of Complex I (NADH dehydrogenase), such as [ND4](/details-gene/4538), [ND2](/details-gene/4536), [ND1](/details-gene/4535), and [ND5](/details-gene/4540), and Complex IV (cytochrome c oxidase), including [COX1](/details-gene/4512), [COX2](/details-gene/4513), and [COX3](/details-gene/4514). Additionally, key nuclear-encoded components of the respiratory chain and ATP synthase, like [COX5B](/details-gene/1329), [ATP5F1B](/details-gene/506), [UQCRB](/details-gene/7381), [COX6C](/details-gene/1345), and [ATP5F1E](/details-gene/514), are also highly significant markers. This coordinated high expression of the entire oxidative phosphorylation machinery is consistent with the cell's massive ATP demand, which is necessary to power the ion pumps (e.g., Na+/K+ ATPase) driving transepithelial transport. * **Protein Synthesis and Transport:** The high significance of genes involved in protein synthesis and trafficking, such as the translation elongation factor [EEF1B2](/details-gene/1933) and the signal recognition particle subunit [SRP14](/details-gene/6727), suggests a robust capacity for producing and maintaining the vast array of transporters, channels, and enzymes located on its apical and basolateral membranes. * **Cellular Adhesion and Structure:** The high specificity score for [CDH9](/details-gene/1007) (Cadherin-9, Effect Size: +1.0000) indicates that a particular type of cell-cell adhesion is a defining feature. This is critical for maintaining the structural integrity of the tubular epithelium, forming a tight barrier that allows for selective, vectorial transport. * **Detoxification and Stress Response:** The prominence of [GSTP1](/details-gene/2950), a glutathione S-transferase, points to a specialized role in detoxification. This is crucial for protecting the cell from reactive oxygen species generated as a byproduct of its high metabolic rate and for metabolizing xenobiotics and drugs that are filtered by the glomerulus. The profile of anti-markers, or genes with low significance, is also informative. The low significance of immediate early genes like [FOS](/details-gene/2353) may suggest a terminally differentiated and functionally stable state. Furthermore, the negative CSI for the non-classical MHC class I molecule [HLA E](/details-gene/3133) could indicate a relatively low level of constitutive interaction with certain immune cells, such as NK cells, compared to other tissues. ## Clinical Significance and Contextual Roles Given the singular focus of the **Overall** context, the analysis highlights the fundamental biology of the [epithelial cell of proximal tubule](/details-cell/CL0002306) and its inherent vulnerabilities. The cell's profound reliance on oxidative phosphorylation makes it exceptionally susceptible to ischemic and toxic insults. Conditions that compromise oxygen or nutrient delivery, or directly inhibit mitochondrial function, can rapidly lead to ATP depletion, loss of ion gradients, cell swelling, and necrosis, which are hallmarks of acute kidney injury (AKI). The high expression of mitochondrial-encoded genes such as [ND4](/details-gene/4538) and [COX1](/details-gene/4512) positions these cells as a primary site of pathology in mitochondrial diseases that can manifest as renal tubulopathies. The significant expression of [GSTP1](/details-gene/2950) underscores the cell's central role in drug metabolism and highlights its susceptibility to drug-induced nephrotoxicity, where the metabolic processing of a compound can lead to the formation of toxic byproducts that damage the tubular epithelium. ## Potential Mechanisms and Research Directions 1. **Hypothesis: Mitochondrial bioenergetics as the primary determinant of cellular vulnerability.** The unique metabolic profile, defined by extremely high and specific expression of mitochondrial genome-encoded electron transport chain components like [ND4](/details-gene/4538) and [COX1](/details-gene/4512), renders the [epithelial cell of proximal tubule](/details-cell/CL0002306) exquisitely sensitive to metabolic insults. This suggests that mitochondrial dysfunction is a primary initiating event in many forms of acute kidney injury (AKI), rather than a secondary consequence of cellular damage. * **Surprising Findings:** While high metabolic activity in these cells is well-established, the data suggest that the *specificity* of this mitochondrial gene signature is a more defining characteristic than many canonical surface markers. The exceptionally high percentile rank scores (PRS < 1%) for numerous mitochondrial genes underscore their remarkable standing relative to all other genes in defining this cell's identity. * **Testable Questions:** Does selective inhibition of specific mitochondrial complexes, whose components (e.g., [ND4](/details-gene/4538) or [COX1](/details-gene/4512)) show top CSI scores, disproportionately affect the viability and reabsorptive capacity of proximal tubule cells compared to other kidney cell types in an ex vivo organoid model? 2. **Hypothesis: Specialized structural and defense mechanisms are integral to proximal tubule identity.** Beyond metabolic activity, the identity and function of the [epithelial cell of proximal tubule](/details-cell/CL0002306) are critically maintained by a specific molecular toolkit for structural integrity and detoxification. The high specificity of [CDH9](/details-gene/1007) (Cadherin-9) suggests it mediates unique cell-cell interactions crucial for tubular architecture, while the high significance of [GSTP1](/details-gene/2950) indicates a specialized, frontline defense mechanism against both xenobiotics and endogenous oxidative stress. * **Surprising Findings:** It is notable that a specific type-II cadherin like [CDH9](/details-gene/1007) appears as a top marker with a perfect effect size of +1.0000. This suggests its expression is highly restricted to this cell type and may play a more specialized role in organizing tubular function than more ubiquitously expressed cadherins. * **Testable Questions:** What is the functional consequence of knocking down [CDH9](/details-gene/1007) on the barrier function, polarity, and polarized transport activity of a proximal tubule epithelial cell monolayer in vitro?