Details for: CL0002062

Cell ID: CL0002062

Cell Name: pulmonary alveolar type 1 cell

Description: A squamous pulmonary alveolar epithelial cell that is flattened and branched. A pulmonary alveolar type 1 cell covers more than 98% of the alveolar surface. This large cell has thin (50-100 nm) cytoplasmic extensions to form the air-blood barrier essential for normal gas exchange.

Synonyms: lung type 1 cells, membranous pneumocytes, pulmonary alveolar type I cell, small alveolar cells, squamous alveolar cell, squamous alveolar lining cell, type 1 alveolar epithelial cells, type I alveolar cells, type I alveolar epithelial cells, type I pneumocyte, AT1, ATI, type 1 pneumocyte

Selected Context(s): Overall

Gene Significance Landscape

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Score:
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Genes

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

Image representation

Depiction of pulmonary alveolar type 1 cell
Courtesy of SwissBioPics

Significant Genes List

Genes with the highest and lowest Percentile Rank Scores (PRS) for pulmonary alveolar type 1 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 pulmonary alveolar type 1 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 pulmonary alveolar type 1 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 pulmonary alveolar type 1 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.

Maximum number of selected genes.
Select a context for the baseline cell.
Select a context for the target cell.
Target Cell for CSI:  pulmonary alveolar type 1 cell (CL0002062)

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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 [pulmonary alveolar type 1 cell](/details-cell/CL0002062), also known as the type I pneumocyte, is a squamous epithelial cell that constitutes the primary structural unit of the lung alveoli, covering over 98% of the alveolar surface. Its extremely thin and branched cytoplasmic extensions form the air-blood barrier, which is essential for efficient gas exchange. **Overall**, the gene significance profile of this cell type points to a highly specialized role that extends beyond a simple passive barrier. The high expression specificity of genes involved in oxidative stress response, such as [GSTP1](/details-gene/2950), and iron metabolism, like [FTH1](/details-gene/2495) and [FTL](/details-gene/2512), suggests that the [pulmonary alveolar type 1 cell](/details-cell/CL0002062) functions as an active metabolic shield, protecting the delicate alveolar structure from inhaled insults. ## Key Characteristics and Function The functional identity of the [pulmonary alveolar type 1 cell](/details-cell/CL0002062) is defined by several key biological themes, as revealed by its top marker genes. * **Oxidative Stress Defense and Detoxification:** A prominent feature is the high significance of genes involved in managing cellular stress. [GSTP1](/details-gene/2950) (CSI: 15.29), a glutathione S-transferase, is crucial for detoxifying reactive oxygen species, a constant threat at the air-liquid interface. This is complemented by the very high significance of both the heavy and light chains of ferritin, [FTH1](/details-gene/2495) (CSI: 16.58) and [FTL](/details-gene/2512) (CSI: 14.06), which sequester intracellular iron, thereby preventing its participation in the generation of hydroxyl radicals. This coordinated system suggests a primary role for this cell in maintaining a low-oxidant microenvironment. * **High Metabolic Activity:** The significant expression of numerous mitochondrial genes, including those encoding subunits of the electron transport chain like [COX1](/details-gene/4512) (CSI: 11.13), [ND2](/details-gene/4536) (CSI: 11.07), and [ND1](/details-gene/4535) (CSI: 10.54), indicates a high energy demand. This metabolic activity is likely required to maintain the vast surface area of the cell, power ion transport across the membrane to regulate alveolar fluid, and support its active defense mechanisms. * **Calcium-Dependent Signaling and Regulation:** The top marker, [S100A6](/details-gene/6277) (CSI: 17.50), is a calcium-binding protein whose expression is inducible by growth factors ([Link](https://pubmed.ncbi.nlm.nih.gov/3755724/)). Together with [CALM2](/details-gene/805) (CSI: 12.31), this points to a sophisticated calcium signaling network. This network may regulate the cell's extensive cytoskeleton, mediate responses to mechanical stretch during breathing, or initiate repair processes following injury. * **Polyamine Metabolism:** The high significance of [SAT1](/details-gene/6303) (CSI: 14.72), the rate-limiting enzyme in polyamine catabolism, and [OAZ1](/details-gene/4946) (CSI: 13.67), an inhibitor of polyamine synthesis, suggests tight regulation of cellular polyamines. This pathway is critical for cell growth and differentiation, and its active modulation in this terminally differentiated cell might be important for cellular homeostasis or response to injury. * **Immune Surveillance:** The presence of [B2M](/details-gene/567) (CSI: 14.63), the light chain of MHC class I molecules, as a top marker suggests the cell's active participation in antigen presentation, allowing it to signal the presence of intracellular pathogens like viruses to the immune system. The anti-marker profile further refines the cell's identity. The low significance of multiple heterogeneous nuclear ribonucleoproteins ([HNRNPC](/details-gene/3183), [HNRNPA1](/details-gene/3178)) and splicing factors ([SRSF5](/details-gene/6430), [RBM39](/details-gene/9584)) is consistent with a terminally differentiated state with a specialized, rather than a globally active, transcriptional and post-transcriptional program. Similarly, the low scores for key glycolytic enzymes like [GAPDH](/details-gene/2597) and [LDHB](/details-gene/3945) align with the high mitochondrial gene signature, suggesting a preference for more efficient aerobic respiration over glycolysis. ## Clinical Significance and Contextual Roles **Overall**, the gene signature of the [pulmonary alveolar type 1 cell](/details-cell/CL0002062) highlights its vulnerability and its defensive posture in the context of lung health and disease. As it forms the primary barrier to the external environment, its integrity is paramount. The pronounced expression of detoxification enzymes like [GSTP1](/details-gene/2950) and iron-sequestering proteins [FTH1](/details-gene/2495) and [FTL](/details-gene/2512) positions this cell type as a critical frontline defender against damage from air pollutants, cigarette smoke, and hyperoxia. Failure of these protective mechanisms could be an initiating event in inflammatory lung diseases such as Chronic Obstructive Pulmonary Disease (COPD) or Acute Respiratory Distress Syndrome (ARDS). The top marker, [S100A6](/details-gene/6277), is of particular interest as its expression is linked to cell proliferation and has been noted in myeloid leukemias ([Link](https://pubmed.ncbi.nlm.nih.gov/3755724/)). While AT1 cells are considered quiescent, their expression of such a potent signaling molecule suggests a role in orchestrating the response to alveolar injury. Dysregulation of [S100A6](/details-gene/6277) signaling could potentially contribute to failed alveolar repair or the development of pulmonary fibrosis. Furthermore, the high significance of [SAT1](/details-gene/6303), a gene involved in the cytotoxic response of lung carcinoma cells to certain therapies ([Link](https://pubmed.ncbi.nlm.nih.gov/1985966/)), underscores its potential relevance in lung cancer biology. The specific expression of [SAT1](/details-gene/6303) in this cell of origin for some lung cancers may influence tumor development or treatment efficacy. ## Potential Mechanisms and Research Directions 1. **Hypothesis:** The [pulmonary alveolar type 1 cell](/details-cell/CL0002062) functions as an active metabolic shield at the air-blood interface, utilizing a robust glutathione- and ferritin-based system ([GSTP1](/details-gene/2950), [FTH1](/details-gene/2495)) to sense and neutralize inhaled oxidants and manage iron, a potent catalyst of reactive oxygen species. This defense system is central to preventing alveolar injury. * **Surprising Findings:** The most specific markers for this cell are not classical structural proteins (e.g., caveolins, aquaporins) but are instead related to cellular defense and metabolism. This reframes the cell's primary role from a passive structural component to an active biochemical gatekeeper. * **Testable Questions:** Does conditional knockout of [GSTP1](/details-gene/2950) or [FTH1](/details-gene/2495) specifically in AT1 cells increase murine susceptibility to lung injury induced by hyperoxia or environmental pollutants like ozone? 2. **Hypothesis:** The calcium-binding protein [S100A6](/details-gene/6277) acts as a critical transducer in the AT1 cell's response to injury, integrating calcium signals elicited by mechanical stress or damage with growth factor pathways to orchestrate repair of the alveolar barrier, potentially by signaling to adjacent progenitor cells. * **Surprising Findings:** A gene strongly associated with cell proliferation and growth factor response, [S100A6](/details-gene/6277) ([Link](https://pubmed.ncbi.nlm.nih.gov/3755724/)), is the most specific marker for a cell traditionally considered terminally differentiated and quiescent. This suggests a previously underappreciated signaling plasticity. * **Testable Questions:** In murine models of acute lung injury (e.g., bleomycin- or LPS-induced), how does the expression and subcellular localization of [S100A6](/details-gene/6277) change within AT1 cells, and does targeted inhibition of [S100A6](/details-gene/6277) impair the kinetics of alveolar epithelial repair?