GO:0045198 establishment of epithelial cell apical/basal polarity: Mechanism, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0045198 describes the specification and formation of apicobasal polarity in epithelial cells, a fundamental process that creates distinct apical and basolateral membrane domains.
• Apical-basal polarity is controlled by conserved protein modules including the PAR, Crumbs, and Scribble complexes, which mutually antagonize each other to define membrane identity.
• Small GTPases such as Rho, Rac, and Cdc42, together with their GEFs and GAPs, are central regulators of polarity establishment.
• Disruption of apical-basal polarity is a hallmark of epithelial cancers and is linked to tumorigenesis, invasion, and metastasis.
• Bacterial pathogens can modulate epithelial polarity to breach host barriers, highlighting its role in infection.
• Emerging tools such as optogenetics and CRISPR-based genome editing enable precise dissection of polarity establishment in space and time.
Description
Epithelial tissues line the surfaces and cavities of the body and form barriers that separate distinct compartments. The establishment of epithelial cell apical/basal polarity (GO:0045198) is the process by which an epithelial cell specifies and forms its apical and basolateral membrane domains, a prerequisite for vectorial transport, barrier function, and tissue morphogenesis. This process is orchestrated by a network of conserved polarity proteins that include the PAR complex (PAR3, PAR6, aPKC), the Crumbs complex (Crb, PALS1, PATJ), and the Scribble module (Scrib, Lgl, Dlg). These modules localize to distinct membrane domains and mutually antagonize each other to maintain domain identity. Understanding GO:0045198 is critical for researchers in cell biology, developmental biology, and cancer biology because loss of polarity is a hallmark of epithelial cancers and is associated with tumor progression and metastasis. Moreover, polarity establishment is dynamically regulated during development, tissue repair, and in response to external cues, and its dysregulation contributes to a range of diseases including cancer and infectious diseases. Recent advances in imaging, optogenetics, and genome editing have provided new insights into the spatiotemporal dynamics of polarity establishment. This article synthesizes current knowledge on the mechanisms, key genes, and research methods relevant to GO:0045198, providing a resource for scientists studying epithelial polarity.
establishment of epithelial cell apical/basal polarity At A Glance
| GO ID | GO:0045198 |
|---|---|
| GO term | establishment of epithelial cell apical/basal polarity |
| Ontology | biological_process |
| Synonym | None |
| Major function | Specification and formation of apical and basolateral membrane domains in epithelial cells |
| Key regulators | PAR complex, Crumbs complex, Scribble module, Rho GTPases |
| Associated diseases | Epithelial cancers, infectious diseases |
| Research methods | Live imaging, optogenetics, CRISPR screens, proteomics |
What Is GO:0045198?
GO:0045198, establishment of epithelial cell apical/basal polarity, is defined as the specification and formation of the apicobasal polarity of an epithelial cell. In other words, it encompasses the molecular and cellular events that lead to the asymmetric organization of an epithelial cell, with distinct apical and basolateral membrane domains, which are essential for epithelial function.
Why Is establishment of epithelial cell apical/basal polarity Important in Cell Biology?
The establishment of epithelial apical/basal polarity is fundamental to tissue architecture and function. It underlies the formation of barriers, directed secretion, and cell-cell adhesion, and its disruption is a key event in the development of epithelial cancers and other diseases. Understanding this process provides insights into normal development and disease pathogenesis, and it offers potential targets for therapeutic intervention.
• Essential for epithelial barrier function and vectorial transport.
• Required for asymmetric cell division and tissue morphogenesis.
• Loss of polarity is a hallmark of epithelial cancers and correlates with poor prognosis.
• Polarity proteins are frequently mutated or misregulated in human tumors.
• Pathogens often target polarity machinery to disrupt host barriers.
• Polarity establishment is crucial for organ development, including gut, kidney, and lung.
• Defects in polarity contribute to developmental disorders and ciliopathies.
• Polarity dynamics are regulated by mechanical and chemical cues from the microenvironment.
• Understanding polarity can inform tissue engineering and regenerative medicine.
• Polarity regulators are potential therapeutic targets in cancer and infectious diseases.
What Happens During establishment of epithelial cell apical/basal polarity?
Initiation and symmetry breaking
In simple terms: The cell first decides which side will be the top (apical) and which will be the bottom/sides (basolateral).
Symmetry breaking is the first step in polarity establishment, where an initially unpolarized epithelial cell receives internal or external cues that define the apical and basolateral axes. This involves the localized activation of Rho GTPases and the recruitment of polarity complexes to specific membrane domains. In many epithelia, cell-cell adhesion and extracellular matrix contacts provide spatial cues that orient the polarity axis.
Assembly of polarity complexes
In simple terms: Specialized protein groups gather at the top and sides to mark each region.
The PAR complex (PAR3, PAR6, aPKC) and the Crumbs complex (Crb, PALS1, PATJ) localize to the apical domain, while the Scribble module (Scrib, Lgl, Dlg) localizes to the basolateral domain. These complexes are mutually antagonistic, ensuring that apical and basolateral identities are mutually exclusive. The recruitment of these complexes is regulated by small GTPases and phospholipid signaling.
Membrane domain specification
In simple terms: The cell builds distinct membrane regions with different proteins and lipids.
Once polarity complexes are in place, they direct the formation of distinct apical and basolateral membrane domains. This involves targeted delivery of proteins and lipids to each domain, as well as the establishment of tight junctions that separate the two domains. The apical domain is enriched in phosphatidylinositol 4,5-bisphosphate (PIP2) and specific lipids, while the basolateral domain has distinct lipid and protein composition.
Cytoskeletal reorganization
In simple terms: The cell's internal skeleton rearranges to support the new shape.
Polarity establishment is accompanied by reorganization of the actin and microtubule cytoskeletons. Actin filaments are enriched at the apical surface, and microtubules are oriented along the apical-basal axis. These cytoskeletal changes are regulated by Rho GTPases and their effectors, and they are essential for maintaining polarity and for processes such as cell division and migration.
Feedback and maintenance
In simple terms: The cell uses feedback loops to keep the top and bottom separate.
Positive and negative feedback loops reinforce the initial polarity cues. For example, aPKC phosphorylates PAR3 and Lgl to exclude them from the apical domain, while the Scribble module promotes basolateral identity and antagonizes apical proteins. This mutual antagonism ensures robust and stable polarity. Additionally, septin filaments contribute to the establishment of polarity through multivalent interactions.
Key Genes Involved in GO:0045198 establishment of epithelial cell apical/basal polarity
The following genes and proteins are key players in the establishment of epithelial cell apical/basal polarity, as supported by the literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| PARD3 (PAR3) | Apical scaffold protein, part of PAR complex | Regulates tight junction assembly and polarity; frequently downregulated in cancers |
| PARD6 (PAR6) | Apical adaptor, binds aPKC and Cdc42 | Essential for apical domain formation; target for polarity studies |
| PRKCI (aPKC) | Apical kinase, phosphorylates polarity substrates | Key regulator of apical identity; oncogenic in some cancers |
| CRB3 (Crumbs3) | Apical transmembrane protein | Defines apical domain; loss impairs polarity and promotes tumorigenesis |
| PALS1 (MPP5) | Apical scaffold, binds Crb | Links Crumbs to tight junctions; mutations linked to ciliopathies |
| PATJ (INADL) | Apical scaffold, part of Crumbs complex | Required for tight junction formation and polarity |
| SCRIB (Scribble) | Basolateral scaffold | Tumor suppressor; loss disrupts polarity and promotes invasion |
| LLGL1/2 (Lgl) | Basolateral protein, antagonizes apical complex | Regulates asymmetric division; downregulated in cancers |
| DLG1 (Dlg) | Basolateral scaffold | Maintains basolateral identity; implicated in cancer and viral oncogenesis |
| CDC42 | Rho GTPase, activates PAR complex | Central regulator of polarity initiation |
| RHOA | Rho GTPase, regulates actomyosin | Controls apical constriction and polarity maintenance |
| RAC1 | Rho GTPase, regulates actin | Promotes apical domain formation |
| ARHGEF7 (β-PIX) | GEF for Rac1/Cdc42 | Activates GTPases at specific sites to establish polarity |
| ARHGAP17 (Nadrin) | GAP for Cdc42 | Terminates GTPase signaling to maintain polarity |
| SEPT6 | Septin filament component | Promotes polarity establishment via multivalent interactions |
| VANGL1/2 | Planar cell polarity core protein | Coordinates planar polarity with apical-basal polarity |
| FZD (Frizzled) | Wnt receptor, planar polarity component | Regulates polarity orientation in Drosophila and vertebrates |
How Is establishment of epithelial cell apical/basal polarity Regulated?
The establishment of epithelial apical/basal polarity is regulated at multiple levels, including transcriptional control of polarity regulators, post-translational modifications such as phosphorylation by aPKC, and GTPase cycling mediated by GEFs and GAPs. Additionally, mechanical cues from the extracellular matrix and cell-cell adhesion receptors modulate polarity orientation. Bacterial pathogens can also modulate polarity signaling to disrupt epithelial barriers.
establishment of epithelial cell apical/basal polarity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SCRIB | Epithelial cancer, tumor suppression | Knockout in human epithelial cell lines (e.g., MCF10A) |
| LLGL1/2 | Cancer, cell polarity defects | Conditional knockout in mouse models |
| PALS1 (MPP5) | Ciliopathy, retinal degeneration | Knock-in of patient mutations in iPSCs |
| CRB3 | Cancer, polarity loss | Overexpression and knockout in 3D organoids |
| CDC42 | Cancer, developmental disorders | Point mutation knock-in in cell lines |
Epithelial cancers
Loss of apical-basal polarity is a hallmark of epithelial cancers and is associated with tumor progression, invasion, and metastasis. Polarity proteins such as Scribble, Lgl, and Dlg are frequently downregulated or mislocalized in human tumors, and their loss promotes uncontrolled proliferation and epithelial-to-mesenchymal transition. For example, Scribble acts as a tumor suppressor, and its depletion disrupts tissue architecture and enhances tumorigenesis in model organisms.
Infectious diseases
Several bacterial pathogens target epithelial polarity to breach host barriers. For instance, Helicobacter pylori and enteropathogenic E. coli can disrupt apical-basal polarity, leading to altered barrier function and inflammation. Understanding how pathogens modulate polarity may inform new therapeutic strategies.
Developmental disorders
Mutations in polarity genes can cause developmental disorders, including ciliopathies and neural tube defects. For example, mutations in PALS1 (MPP5) are linked to severe ciliopathies, and disruption of polarity in Drosophila leads to developmental defects.
From establishment of epithelial cell apical/basal polarity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of Scribble disrupt polarity and promote invasion? | SCRIB knockout in MCF10A cells |
| How does aPKC phosphorylation regulate PAR3 localization? | Point mutation of aPKC phosphorylation sites in PAR3 |
| Can restored Crumbs expression rescue polarity in cancer cells? | CRB3 knock-in overexpression in cancer cell lines |
| What is the role of Septin 6 in polarity establishment? | SEPT6 knockout and tagged knock-in in epithelial cells |
| How do bacterial pathogens modulate polarity? | Infection of polarized epithelial cells with H. pylori |
| What is the spatiotemporal dynamics of polarity establishment? | Optogenetic control of Rho GTPases in live cells |
How to Study the establishment of epithelial cell apical/basal polarity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Live-cell imaging | Dynamics of polarity protein localization | Visualizing PAR complex assembly |
| Optogenetics | Light-controlled manipulation of signaling | Dissecting Rho GTPase function in polarity |
| CRISPR knockout screens | Gene requirement for polarity | Identifying novel polarity regulators |
| Proteomics (AP-MS) | Protein interactions | Mapping polarity complex components |
| RNA-seq | Transcriptional changes | Identifying polarity-regulated genes |
| Immunofluorescence | Protein localization and domain markers | Assessing polarity in tissues and cells |
| Organoid culture | 3D tissue architecture | Modeling epithelial polarity in vitro |
| GTPase activity assays | GTPase activation state | Measuring Rho GTPase cycling |
Live-cell imaging
Live-cell imaging using fluorescently tagged polarity proteins allows real-time visualization of polarity establishment. This method can reveal the dynamics of PAR complex assembly and membrane domain formation.
Optogenetics
Optogenetic tools enable precise spatiotemporal control of signaling molecules such as Rho GTPases, allowing researchers to manipulate polarity establishment with light. This approach has been used to dissect the shared mechanisms of polarity and mitosis.
CRISPR screens
Genome-wide CRISPR knockout screens can identify novel regulators of epithelial polarity. Such screens have uncovered genes involved in membrane trafficking and signaling that are required for polarity establishment.
Proteomics
Proteomic approaches, including affinity purification and mass spectrometry, can identify protein-protein interactions within polarity complexes. These methods help define the composition and dynamics of polarity modules.
How CRISPR Can Be Used to Study GO:0045198 establishment of epithelial cell apical/basal polarity
Knockout
CRISPR knockout of polarity genes such as SCRIB, LLGL1, or CRB3 in epithelial cell lines can disrupt apical-basal polarity, leading to loss of domain markers and altered morphology. These models are valuable for studying the consequences of polarity loss in cancer and development.
Point Mutation
Introducing point mutations in polarity genes, such as phosphorylation sites in PAR3 or GTPase-activating residues in CDC42, allows precise dissection of signaling events. For example, mutation of aPKC phosphorylation sites in PAR3 can reveal their role in polarity establishment.
Knock-in
Knock-in of fluorescent tags (e.g., GFP) into endogenous polarity genes enables real-time tracking of protein localization and dynamics. Tagged knock-in of SEPT6 has been used to study its role in polarity establishment.
Overexpression
Overexpression of polarity genes, such as CRB3 or PARD3, can rescue polarity defects or induce ectopic polarity. This approach is useful for gain-of-function studies and for testing sufficiency of a gene in polarity establishment.
How EDITGENE Supports establishment of epithelial cell apical/basal polarity Research
Researchers studying establishment of epithelial cell apical/basal polarity-related genes often need to determine whether a candidate gene is causally involved in polarity establishment, and to dissect its precise function using targeted genome editing. EDITGENE provides a comprehensive suite of CRISPR services to accelerate this research.
Contact EDITGENE today to design your custom CRISPR model for establishment of epithelial cell apical/basal polarity research.
Related Products
| Product name | Cat.No. | Species | Gene ID | |
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| EZR Knockout HEK293 Cell Line | EDJ-KQ3384 | Human | 7430 | Details Get a Quote |
| MSN Knockout HEK293 Cell Line | EDJ-KQ3822 | Human | 4478 | Details Get a Quote |
| NHERF1 Knockout HEK293 Cell Line | EDJ-KQ3929 | Human | 9368 | Details Get a Quote |
| MYO9A Knockout HEK293 Cell Line | EDJ-KQ5294 | Human | 4649 | Details Get a Quote |
| OPHN1 Knockout HEK293 Cell Line | EDJ-KQ5381 | Human | 4983 | Details Get a Quote |
| CAMSAP3 Knockout HEK293 Cell Line | EDJ-KQ12719 | Human | 57662 | Details Get a Quote |
| SYNE4 Knockout HEK293 Cell Line | EDJ-KQ14799 | Human | 163183 | Details Get a Quote |
| CDC42 Knockout A-549 Cell Line | EDJ-KQ18123 | Human | 998 | Details Get a Quote |
| EZR Knockout A-549 Cell Line | EDJ-KQ25070 | Human | 7430 | Details Get a Quote |
| EZR Knockout HCT 116 Cell Line | EDJ-KQ25071 | Human | 7430 | Details Get a Quote |
| EZR Knockout HeLa Cell Line | EDJ-KQ25072 | Human | 7430 | Details Get a Quote |
| MSN Knockout A-549 Cell Line | EDJ-KQ25961 | Human | 4478 | Details Get a Quote |
| MSN Knockout HCT 116 Cell Line | EDJ-KQ25962 | Human | 4478 | Details Get a Quote |
| NHERF1 Knockout A-549 Cell Line | EDJ-KQ26166 | Human | 9368 | Details Get a Quote |
| NHERF1 Knockout HCT 116 Cell Line | EDJ-KQ26167 | Human | 9368 | Details Get a Quote |
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Frequently Asked Questions About establishment of epithelial cell apical/basal polarity
What is GO:0045198?
GO:0045198 is the Gene Ontology term for the establishment of epithelial cell apical/basal polarity, defined as the specification and formation of the apicobasal polarity of an epithelial cell.
What genes are involved in establishment of epithelial cell apical/basal polarity?
Key genes include PARD3, PARD6, PRKCI, CRB3, PALS1, PATJ, SCRIB, LLGL1/2, DLG1, CDC42, RHOA, RAC1, and SEPT6, among others.
Why is apical-basal polarity important?
Apical-basal polarity is essential for epithelial barrier function, tissue morphogenesis, and asymmetric cell division; its loss is a hallmark of cancer.
How is apical-basal polarity established?
It is established through symmetry breaking, assembly of polarity complexes (PAR, Crumbs, Scribble), membrane domain specification, cytoskeletal reorganization, and feedback loops.
What diseases are associated with defects in epithelial polarity?
Defects in epithelial polarity are associated with epithelial cancers, infectious diseases, and developmental disorders such as ciliopathies.
What methods are used to study apical-basal polarity?
Common methods include live-cell imaging, optogenetics, CRISPR screens, proteomics, and organoid culture.
How do bacterial pathogens affect epithelial polarity?
Some bacterial pathogens modulate polarity signaling to disrupt epithelial barriers, aiding infection and inflammation.
What is the role of Rho GTPases in polarity?
Rho GTPases such as Cdc42, Rac1, and RhoA regulate polarity establishment by controlling cytoskeletal dynamics and polarity complex localization.
Can CRISPR be used to study polarity genes?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are powerful tools to dissect polarity gene function.
What is the difference between apical-basal polarity and planar cell polarity?
Apical-basal polarity refers to the top-bottom axis of an epithelial cell, while planar cell polarity refers to the coordinated orientation of cells within the plane of a tissue.
Conclusion
The establishment of epithelial cell apical/basal polarity (GO:0045198) is a fundamental biological process that governs epithelial architecture and function. Its dysregulation is implicated in cancer, infectious diseases, and developmental disorders. Continued research using advanced tools such as CRISPR genome editing and optogenetics will further illuminate the mechanisms and therapeutic potential of targeting polarity pathways.
References
- 1. Buckley CE et al.. 2022. Apical-basal polarity and the control of epithelial form and function.. Nat Rev Mol Cell Biol 23(8):559-577 PMID: 35440694
- 2. Rust K et al.. 2021. Transcriptional Control of Apical-Basal Polarity Regulators.. Int J Mol Sci 22(22) PMID: 34830224
- 3. Thottacherry JJ et al.. 2023. Apical-basal polarity in the gut.. Semin Cell Dev Biol 150-151:15-22 PMID: 36670034
- 4. Fu W et al.. 2025. Multivalent interactions of Septin 6 promote the establishment of epithelial cell polarity.. J Mol Cell Biol 17(1) PMID: 39973116
- 5. Tapia R et al.. 2017. Modulation of epithelial cell polarity by bacterial pathogens.. Ann N Y Acad Sci 1405(1):16-24 PMID: 28628193
- 6. Ngok SP et al.. 2014. Establishment of epithelial polarity--GEF who's minding the GAP?. J Cell Sci 127(Pt 15):3205-15 PMID: 24994932
- 7. Carvajal-Gonzalez JM et al.. 2014. Mechanisms of planar cell polarity establishment in Drosophila.. F1000Prime Rep 6:98 PMID: 25580252
- 8. Crellin HA et al.. 2024. Using Optogenetics to Investigate the Shared Mechanisms of Apical-Basal Polarity and Mitosis.. Cells Tissues Organs 213(2):161-180 PMID: 36599311
