Details for: CL0000138

Cell ID: CL0000138

Cell Name: chondrocyte

Description: A skeletogenic cell that secretes a specialized, avascular, GAG-rich matrix, is embedded in cartilage tissue matrix, retains the ability to divide, and develops from a chondroblast cell.

Synonyms: cartilage cell

Selected Context(s): Overall

Gene Significance Landscape

Display Options
Score:
Display
Genes

Contexts:

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 chondrocyte 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 chondrocyte. 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 chondrocyte. 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 chondrocyte. 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:  chondrocyte (CL0000138)

 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.

Loading network (please wait)...

## Summary The [chondrocyte](/details-cell/CL0000138), or cartilage cell, is a skeletogenic cell type primarily responsible for secreting and maintaining the specialized, avascular, glycosaminoglycan-rich extracellular matrix of cartilage. Gene significance analysis reveals a highly distinctive molecular identity for this cell, defined not only by its matrix-related functions but also by an unexpected and highly specific expression of genes typically associated with detoxification and specialized sensory structures. The top markers, including the UDP-glucuronosyltransferase [UGT1A8](/details-gene/54576) and the inner-ear structural protein Stereocilin ([STRC](/details-gene/161497)), suggest that [chondrocytes](/details-cell/CL0000138) possess unique metabolic and mechanostructural capabilities that extend beyond their classically defined role in skeletal biology. ## Key Characteristics and Function Analysis of gene expression specificity (**Overall** context) highlights several functional clusters that define the [chondrocyte](/details-cell/CL0000138) phenotype. * **Specialized Metabolic and Detoxification Program:** The most specific marker is [UGT1A8](/details-gene/54576), an enzyme involved in Phase II metabolism that conjugates lipophilic compounds, facilitating their excretion. Its high specificity (CSI Z-Score: 62.97) suggests [chondrocytes](/details-cell/CL0000138) have a robust, intrinsic capacity to metabolize and neutralize endogenous or exogenous substances within the isolated cartilage matrix. This is further supported by the specific expression of [GALNT9](/details-gene/50614), a glycosyltransferase responsible for O-linked glycosylation, a critical post-translational modification for many secreted matrix proteins. * **Unique Structural and Adhesion Machinery:** The second most specific gene, [STRC](/details-gene/161497), encodes Stereocilin, a protein essential for the cohesion of stereocilia in the inner ear ([Link](https://doi.org/10.1038/ng726)). Its high specificity in [chondrocytes](/details-cell/CL0000138) is a striking finding and may indicate a novel role in organizing the extracellular matrix or mediating cell-matrix adhesion, potentially related to mechanosensation in a manner analogous to its function in hearing. This theme of cell adhesion is reinforced by the significant expression of [PCDHB15](/details-gene/56121), a protocadherin. * **Distinct Regulatory and Signaling Pathways:** The profile includes specific transcription factors such as [DBX2](/details-gene/440097) and signaling molecules like [MAPK15](/details-gene/225689) (ERK8), indicating that unique transcriptional programs and signaling cascades govern the [chondrocyte's](/details-cell/CL0000138) specialized state. The expression of [PRND](/details-gene/23627), encoding the prion-like protein Doppel, further points to unconventional signaling or protein-protein interactions being important for this cell type. The anti-marker profile helps to refine this cell's identity. The low specificity scores for ubiquitous housekeeping genes like [GAPDH](/details-gene/2597) and [CALM1](/details-gene/801) are expected in a z-score based analysis. More surprisingly, the low specificity of [COL11A2](/details-gene/1302), a gene for a key fibrillar collagen in cartilage, suggests that its expression, while functionally critical, is not as uniquely restricted to [chondrocytes](/details-cell/CL0000138) as the top markers in this dataset. Additionally, the negative scores for immune-related genes such as [HLA E](/details-gene/3133) are consistent with the [chondrocyte's](/details-cell/CL0000138) non-hematopoietic lineage. ## Clinical Significance and Contextual Roles The unique gene signature of [chondrocytes](/details-cell/CL0000138) has significant clinical implications, particularly for skeletal and metabolic disorders. * The high specificity of [STRC](/details-gene/161497), a gene whose mutations are a known cause of autosomal recessive non-syndromic deafness ([Link](https://doi.org/10.1038/ng726)), is a novel discovery. This finding could suggest an unrecognized link between cartilage biology and auditory function, perhaps through shared requirements for specific types of mechanostructural proteins. It may also implicate [STRC](/details-gene/161497) as a potential player in cartilage pathologies where mechanotransduction is disrupted, such as osteoarthritis. * The prominence of [UGT1A8](/details-gene/54576), an enzyme involved in the metabolism of drugs and endogenous compounds ([Link](https://doi.org/10.1097/00008571-200206000-00004)), suggests that [chondrocyte](/details-cell/CL0000138) metabolism could influence the efficacy and toxicity of intra-articular therapies. Variations in [UGT1A8](/details-gene/54576) activity might affect how patients with joint diseases respond to treatment or clear inflammatory mediators. * The expression of [PRND](/details-gene/23627), whose upregulation in the CNS is associated with ataxia in prion-protein deficient mice ([Link](https://doi.org/10.1006/jmbi.1999.3108)), is intriguing. While its function in cartilage is unknown, its presence suggests that pathways related to protein folding and copper homeostasis might be important for [chondrocyte](/details-cell/CL0000138) health and disease. ## Potential Mechanisms and Research Directions 1. **Hypothesis:** The high expression specificity of [STRC](/details-gene/161497), a gene crucial for the structural integrity of inner ear stereocilia, suggests it performs a similar mechanosensory or structural anchoring role in the cartilage extracellular matrix, potentially linking [chondrocytes](/details-cell/CL0000138) to the surrounding matrix and mediating responses to mechanical load. * **Surprising Findings:** The most prominent marker for a [skeletogenic cell](/details-cell/CL0000138) is a gene almost exclusively studied in the context of the inner ear. This challenges the conventional view of chondrocyte-specific structural proteins, which typically focuses on collagens and proteoglycans. * **Testable Questions:** Does conditional knockout of [STRC](/details-gene/161497) in chondrocytes lead to defects in cartilage matrix organization, altered biomechanical properties, or an impaired response to mechanical stress, potentially predisposing to osteoarthritis-like changes? 2. **Hypothesis:** The high specificity of the detoxification enzyme [UGT1A8](/details-gene/54576) indicates that [chondrocytes](/details-cell/CL0000138) possess a specialized metabolic barrier function within the avascular cartilage matrix. This allows them to locally conjugate and neutralize metabolic byproducts or xenobiotics that might otherwise accumulate and cause damage. * **Surprising Findings:** [Chondrocytes](/details-cell/CL0000138) are not typically viewed as major players in xenobiotic metabolism, a role usually ascribed to the liver or gut. The discovery of a highly specific UGT isoform suggests a level of metabolic autonomy and a protective role not previously appreciated. * **Testable Questions:** Can human [chondrocytes](/details-cell/CL0000138) in vitro metabolize known [UGT1A8](/details-gene/54576) substrates, and does inhibition or knockdown of [UGT1A8](/details-gene/54576) render these cells more susceptible to damage from pro-inflammatory lipids or specific drugs?