GO:0034669 integrin alpha4-beta7 complex: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0034669 (integrin alpha4-beta7 complex) is a heterodimeric cellular_component composed of one ITGA4 (alpha4) subunit and one ITGB7 (beta7) subunit.
• The alpha4-beta7 integrin is the principal gut-homing receptor on lymphocytes, binding MAdCAM-1 and VCAM-1 to direct cells to intestinal tissue.
• alpha4-beta7 expression is regulated by TGF-beta1 through the ITGB7 promoter, linking cytokine signaling to intestinal immune homing.
• The complex is a clinically validated drug target, exemplified by the anti-alpha4-beta7 antibody vedolizumab used in inflammatory bowel disease.
• alpha4-beta7 is a key HIV-1 attachment factor, and host proteins including integrins are incorporated into the viral envelope.
• alpha4-beta7-bearing cell populations can be studied with CRISPR knockout, knock-in reporters, and multi-omics approaches.
Description
The integrin alpha4-beta7 complex (GO:0034669) is a heterodimeric cell-surface adhesion receptor in the integrin family, defined in QuickGO as an integrin complex that comprises one alpha4 subunit and one beta7 subunit. It is a cellular_component term, meaning it describes a specific molecular machine rather than a process or activity. The complex is best known as the gut-homing receptor on lymphocytes, where it mediates adhesion to mucosal addressin cell adhesion molecule-1 (MAdCAM-1) and vascular cell adhesion molecule-1 (VCAM-1). Because of this role, the alpha4-beta7 integrin is a central node in intestinal immunity and a validated therapeutic target in inflammatory bowel disease. For researchers, GO:0034669 provides a precise annotation target when studying leukocyte trafficking, mucosal immunity, and HIV-1 pathogenesis. The complex is dynamically regulated: TGF-beta1 controls ITGB7 promoter activity, and inflammatory cytokines such as IL-12 can expand alpha4-beta7-positive intestinal T-lymphocyte subsets. These features make the complex an attractive model for dissecting how adhesion receptors integrate environmental signals into cell migration and tissue retention. Recent work has extended the relevance of alpha4-beta7 beyond classical gut immunology. Multi-omics analyses have implicated terminal ileum-derived IgA-positive beta7-positive cells in IgA nephropathy, and long-term follow-up of gastrointestinal CAR T-cell lymphoma has highlighted the importance of homing receptors in chimeric antigen receptor T-cell biology. In parallel, HIV research continues to identify alpha4-beta7 and other host proteins as contributors to viral attachment and envelope incorporation. Together, these findings position GO:0034669 as a convergence point for immunology, virology, and translational medicine.
integrin alpha4-beta7 complex At A Glance
| GO ID | GO:0034669 |
|---|---|
| GO term | integrin alpha4-beta7 complex |
| Ontology | cellular_component |
| Synonym | alpha4-beta7 integrin complex; ITGA4-ITGB7 complex |
| Definition | An integrin complex that comprises one alpha4 subunit and one beta7 subunit. |
| Major function | Gut-homing adhesion receptor that binds MAdCAM-1 and VCAM-1 on lymphocytes |
| Subunit composition | One ITGA4 (alpha4) subunit plus one ITGB7 (beta7) subunit |
| Key ligands | MAdCAM-1, VCAM-1, and fibronectin-associated ligands |
| Expression context | Intestinal T-lymphocyte subsets and IgA-positive beta7-positive cells |
| Clinical relevance | Target of vedolizumab in inflammatory bowel disease and HIV-1 attachment factor |
What Is GO:0034669?
In our own words, GO:0034669 describes a non-covalent heterodimeric integrin receptor formed by the pairing of one alpha4 (ITGA4) subunit with one beta7 (ITGB7) subunit. The term is a cellular_component annotation, so it refers to the assembled receptor complex at the membrane, not to the individual subunits or to a signaling pathway. The complex functions as an adhesion receptor that binds extracellular matrix and cellular ligands, thereby linking the exterior environment to intracellular signaling and cytoskeletal reorganization.
Why Is integrin alpha4-beta7 complex Important in Cell Biology?
GO:0034669 is important because the alpha4-beta7 integrin sits at the interface between immune cell trafficking and tissue-specific immunity. It is the dominant gut-homing receptor that allows lymphocytes to leave the circulation and enter intestinal tissue, a process essential for mucosal defense and for the pathogenesis of inflammatory bowel disease. Because the complex is selectively expressed on a subset of leukocytes, it has become a druggable target, and anti-alpha4-beta7 biologics are used clinically to reduce intestinal inflammation. Beyond immunology, alpha4-beta7 is a recognized HIV-1 attachment factor, and host integrins can be incorporated into the viral envelope, making the complex relevant to viral entry and pathogenesis. Finally, the complex is a tractable model for studying integrin heterodimer assembly, ligand binding specificity, and signal transduction, all of which are fundamental cell biology questions.
• Defines the gut-homing phenotype of lymphocytes through MAdCAM-1 and VCAM-1 binding.
• Serves as the molecular target of vedolizumab and related anti-integrin therapeutics in inflammatory bowel disease.
• Links TGF-beta1 signaling to ITGB7 promoter activity and intestinal immune homing.
• Contributes to HIV-1 attachment and host protein incorporation into the viral envelope.
• Marks IgA-positive beta7-positive cell populations implicated in IgA nephropathy.
• Is relevant to CAR T-cell homing and gastrointestinal CAR T-cell lymphoma biology.
• Provides a model for integrin heterodimer assembly and subunit-specific ligand recognition.
• Enables CRISPR-based dissection of leukocyte trafficking and mucosal immunity.
• Connects cytokine-driven inflammation to expansion of alpha4-beta7-positive T-cell subsets.
• Supports biomarker development for HIV acquisition risk and mucosal immunity.
Structure and Composition of integrin alpha4-beta7 complex
Heterodimer Assembly of ITGA4 and ITGB7
In simple terms: The complex is built from two different protein chains that pair up to form one functional receptor.
The integrin alpha4-beta7 complex is a non-covalent heterodimer assembled from one alpha4 (ITGA4) subunit and one beta7 (ITGB7) subunit. Each subunit is a type I transmembrane glycoprotein with a large extracellular domain, a single transmembrane helix, and a short cytoplasmic tail. The alpha4 subunit contributes the ligand-binding headpiece, while the beta7 subunit provides structural support and intracellular signaling capacity. Assembly occurs in the endoplasmic reticulum and the heterodimer is then transported to the plasma membrane, where it adopts an inactive, bent conformation until activated.
Ligand-Binding Headpiece and Specificity
In simple terms: The head of the receptor is the part that grabs onto partner molecules on other cells or in the matrix.
The extracellular headpiece of alpha4-beta7 recognizes specific ligands, most notably MAdCAM-1 and VCAM-1, which are expressed on high endothelial venules and activated endothelium. This ligand specificity is what confers gut-homing properties on lymphocytes, because MAdCAM-1 is enriched in intestinal mucosal vasculature. The alpha4 subunit also contains a metal ion-dependent adhesion site (MIDAS) that coordinates a divalent cation required for ligand binding. Structural rearrangements in the headpiece upon activation convert the receptor from a low-affinity to a high-affinity state.
Transmembrane and Cytoplasmic Domains
In simple terms: The part of the receptor inside the cell transmits signals and connects to the cytoskeleton.
The transmembrane helices of ITGA4 and ITGB7 associate tightly and participate in conformational signaling. The cytoplasmic tails are short but critical: they bind intracellular adaptors such as talin and kindlin, which trigger inside-out activation and link the receptor to the actin cytoskeleton. These domains also contain motifs that mediate endocytosis and recycling, allowing the complex to be redistributed to the leading edge of migrating cells. Phosphorylation and other post-translational modifications of the cytoplasmic tails modulate these interactions.
Conformational States and Activation
In simple terms: The receptor can switch between a relaxed and a gripping shape, like a hand opening and closing.
Integrin alpha4-beta7 exists in at least three conformational states: a bent, low-affinity state; an extended, intermediate-affinity state; and an extended, high-affinity state with an open headpiece. Transition between these states is driven by inside-out signaling from chemokine receptors and by ligand engagement (outside-in signaling). The beta7 subunit cytoplasmic tail is a key node for inside-out activation, and mutations that lock the receptor in a particular conformation alter lymphocyte adhesion and migration. This dynamic regulation ensures that the complex is activated only in the appropriate vascular context.
Interaction with the Actin Cytoskeleton and Signaling Complexes
In simple terms: Once the receptor grips its target, it pulls on the cell's internal skeleton to help the cell crawl.
Ligand-bound alpha4-beta7 clusters at the plasma membrane and recruits talin, kindlin, paxillin, and focal adhesion kinase, thereby coupling to the actin cytoskeleton. This coupling generates traction forces that support lymphocyte arrest, spreading, and transendothelial migration. Downstream signaling through focal adhesion kinase and Src-family kinases modulates cell survival, proliferation, and cytokine production. The complex also cooperates with chemokine receptors, which provide the initial activation signal that converts the receptor to a high-affinity state.
Key Genes Involved in GO:0034669 integrin alpha4-beta7 complex
The following genes and proteins are the principal molecular players associated with the integrin alpha4-beta7 complex (GO:0034669), based on the verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| ITGA4 | Encodes the alpha4 integrin subunit of the alpha4-beta7 heterodimer | Core subunit; knockout abolishes complex formation and gut homing |
| ITGB7 | Encodes the beta7 integrin subunit; promoter is TGF-beta1 responsive | Regulatory node linking cytokine signaling to homing |
| MADCAM1 | Primary endothelial ligand for alpha4-beta7 in gut mucosa | Target for blocking intestinal lymphocyte recruitment |
| VCAM1 | Alternative ligand for alpha4-beta7 on activated endothelium | Mediates adhesion outside the gut; inflammation marker |
| TGFB1 | Cytokine that activates the ITGB7 promoter | Upstream regulator of beta7 expression |
| IL12 | Cytokine that expands alpha4-beta7-positive intestinal T-cell subsets | Inflammatory driver of homing receptor expression |
| CD4 | Marker of T-helper cells that express alpha4-beta7 | Defines the major alpha4-beta7-positive lymphocyte subset |
| CD8 | Marker of cytotoxic T cells that can express alpha4-beta7 | Relevant to mucosal cytotoxic immunity |
| IGHA1 | IgA heavy chain associated with beta7-positive plasma cells | Links alpha4-beta7 to mucosal IgA responses |
| ITGB1 | Beta1 integrin that can pair with alpha4 as an alternative heterodimer | Context for beta7-specific versus beta1-specific functions |
| TLN1 | Talin, an adaptor that activates integrins and links to actin | Key inside-out signaling component |
| FERMT2 | Kindlin-2, an integrin-activating adaptor | Modulates integrin affinity and adhesion |
| PTK2 | Focal adhesion kinase downstream of integrin ligation | Signaling effector for adhesion-dependent survival |
| SRC | Src-family kinase that propagates integrin signals | Mediator of outside-in signaling |
| CXCR4 | Chemokine receptor that cooperates with integrins in homing | Provides activation cues for integrin affinity switching |
| CCR9 | Gut-homing chemokine receptor co-expressed with alpha4-beta7 | Combinatorial marker of intestinal tropism |
| CD44 | Adhesion molecule that cooperates in leukocyte extravasation | Context-dependent co-receptor in migration |
| ACTB | Beta-actin, the cytoskeletal substrate for integrin traction | Readout for cytoskeletal coupling |
How Is integrin alpha4-beta7 complex Regulated?
The expression and activity of the integrin alpha4-beta7 complex are regulated at multiple levels. Transcriptionally, the ITGB7 promoter is responsive to TGF-beta1, which defines control regions that govern beta7 expression in lymphoid cells. Inflammatory cytokines such as IL-12 can expand intestinal T-lymphocyte subsets bearing alpha4-beta7, indicating that the cytokine milieu shapes the size of the alpha4-beta7-positive population. At the protein level, the complex is regulated by inside-out signaling: chemokine receptors and other G-protein-coupled receptors trigger talin and kindlin binding to the beta7 cytoplasmic tail, converting the receptor to a high-affinity state. Outside-in signaling following ligand binding further modulates cytoskeletal coupling and downstream kinase activity. Finally, endocytic recycling and post-translational modifications of the cytoplasmic tails provide additional layers of control over surface levels and activity.
integrin alpha4-beta7 complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| ITGA4 | Inflammatory bowel disease; lymphocyte gut homing | ITGA4 knockout Jurkat or primary T-cell model |
| ITGB7 | Mucosal inflammation; TGF-beta1-responsive expression | ITGB7 promoter reporter knock-in cell line |
| MADCAM1 | Intestinal inflammation; leukocyte recruitment | MAdCAM-1 overexpression endothelial cell model |
| IGHA1 | IgA nephropathy; mucosal IgA axis | IgA-positive beta7-positive cell multi-omics model |
| ITGB7 | HIV-1 attachment and envelope incorporation | ITGB7 knockout CD4-positive T-cell line for viral entry assays |
Inflammatory Bowel Disease and Mucosal Inflammation
The alpha4-beta7 integrin is the dominant gut-homing receptor, and its interaction with MAdCAM-1 is a rate-limiting step in lymphocyte recruitment to the intestinal mucosa. In inflammatory bowel disease, excessive alpha4-beta7-mediated trafficking contributes to mucosal inflammation, and blockade of the complex with the anti-alpha4-beta7 antibody vedolizumab reduces intestinal inflammation. This clinical success validates GO:0034669 as a therapeutic target and provides a rationale for studying its regulation in disease models.
IgA Nephropathy and Mucosal Immune Axis
Multi-omics analyses have revealed a pathogenic role for terminal ileum-derived IgA-positive beta7-positive cells in IgA nephropathy. These cells express the alpha4-beta7 complex, which directs them to mucosal sites and potentially to the kidney, linking intestinal immunity to renal disease. This finding expands the disease relevance of GO:0034669 beyond the gut and suggests that alpha4-beta7-positive cell populations could serve as biomarkers or therapeutic targets in IgA nephropathy.
HIV-1 Infection and Viral Attachment
The alpha4-beta7 integrin is a recognized HIV-1 attachment factor, and host proteins including integrins can be incorporated into the external HIV-1 envelope. This interaction may facilitate viral binding to target cells and contribute to pathogenesis. alpha4-beta7 has also been investigated as a predictor of HIV acquisition, although its role is best understood as one thread in a complex tapestry of host and viral determinants. These studies position GO:0034669 at the intersection of virology and mucosal immunology.
Gastrointestinal CAR T-Cell Lymphoma and Homing
Long-term follow-up of gastrointestinal CAR T-cell lymphoma has highlighted the importance of homing receptors in chimeric antigen receptor T-cell biology. Because alpha4-beta7 mediates gut homing, it may influence the localization and expansion of CAR T cells in the gastrointestinal tract. Understanding how the complex contributes to T-cell trafficking could inform the design of safer CAR T-cell therapies and help manage gastrointestinal complications.
From integrin alpha4-beta7 complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of ITGA4 abolish alpha4-beta7 complex formation and gut homing? | ITGA4 knockout cell line or primary T cells |
| Does a point mutation in the ITGB7 cytoplasmic tail alter inside-out activation? | ITGB7 point-mutation knock-in cell line |
| Can a fluorescent reporter track alpha4-beta7 surface expression? | ITGB7 tagged knock-in with fluorescent tag |
| Does overexpression of alpha4-beta7 enhance adhesion to MAdCAM-1? | ITGA4/ITGB7 double overexpression cell line |
| Which genes regulate alpha4-beta7-dependent migration? | CRISPR library screening in a migration assay |
| Does TGF-beta1 regulate ITGB7 promoter activity? | ITGB7 promoter reporter knock-in cell line |
How to Study the integrin alpha4-beta7 complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Flow cytometry | Surface expression of alpha4-beta7 heterodimer | Immunophenotyping of lymphocyte subsets |
| Static adhesion assay | Binding to immobilized MAdCAM-1 or VCAM-1 | Functional assessment of receptor affinity |
| Transendothelial migration assay | Ability of cells to migrate across endothelium | Gut-homing functional readout |
| RNA sequencing | Transcriptional program of alpha4-beta7-positive cells | Discovery of co-regulated genes |
| Proteomics | Protein interactions and modifications | Identification of complex components |
| Confocal microscopy | Subcellular localization and clustering | Visualization of adhesion structures |
| CRISPR knockout screening | Genes required for alpha4-beta7 function | Pathway discovery in migration assays |
| Promoter reporter assay | ITGB7 promoter activity | TGF-beta1 responsiveness studies |
Flow Cytometry and Antibody-Based Detection
Flow cytometry using antibodies specific for the alpha4-beta7 heterodimer is the standard method to quantify surface expression on lymphocytes and other cell types. This approach can resolve co-expression with markers such as CD4, CD8, CCR9, and IgA, enabling precise immunophenotyping of alpha4-beta7-positive populations. It is also used to monitor receptor internalization and recycling after ligand engagement.
Adhesion and Migration Assays
Static and flow-based adhesion assays measure the ability of alpha4-beta7-expressing cells to bind immobilized MAdCAM-1 or VCAM-1. Transendothelial migration assays further assess the functional consequence of receptor activation. These assays are essential for testing whether CRISPR-mediated knockout or point mutations alter the adhesive properties of the complex.
Multi-Omics and Transcriptomics
Multi-omics analyses, including transcriptomics and proteomics, have been used to characterize IgA-positive beta7-positive cell populations in IgA nephropathy. RNA sequencing can define the transcriptional program associated with alpha4-beta7 expression, while proteomics can identify interacting proteins and post-translational modifications. These approaches are powerful for discovering novel regulators of the complex.
Imaging and Structural Approaches
Confocal and super-resolution microscopy can visualize alpha4-beta7 clustering at the plasma membrane and its co-localization with talin, kindlin, and actin. Structural studies, including crystallography and cryo-electron microscopy, have revealed the conformational states of integrin heterodimers and the basis of ligand specificity. Together, imaging and structural methods provide mechanistic insight into how the complex functions.
How CRISPR Can Be Used to Study GO:0034669 integrin alpha4-beta7 complex
Knockout
CRISPR knockout of ITGA4 or ITGB7 is the most direct way to abolish the integrin alpha4-beta7 complex and test its function. Knockout cell lines or primary T cells can be used to measure loss of adhesion to MAdCAM-1 and VCAM-1, impaired gut homing, and altered downstream signaling. These models are essential for validating whether a candidate gene acts through the complex rather than through a parallel pathway.
Point Mutation
Point mutations in the ITGB7 cytoplasmic tail or in the alpha4 ligand-binding domain can dissect specific functions without eliminating the protein. For example, mutations that disrupt talin or kindlin binding sites can lock the receptor in a low-affinity state, while mutations in the MIDAS motif can impair ligand binding. These knock-in models provide fine-grained mechanistic insight into inside-out and outside-in signaling.
Knock-in
Knock-in of fluorescent or epitope tags into ITGA4 or ITGB7 allows real-time tracking of the complex at the plasma membrane and in intracellular compartments. Tagged knock-in models can be combined with live-cell imaging to study receptor trafficking, clustering, and turnover. They also enable proximity labeling to identify novel interacting proteins.
Overexpression
Overexpression of ITGA4 and ITGB7 together can create a gain-of-function model to study enhanced adhesion, migration, and signaling. This approach is useful for testing whether increased surface levels of the complex are sufficient to drive gut homing or to alter cell survival. Overexpression models can also be used in drug screening to identify inhibitors of alpha4-beta7 function.
How EDITGENE Supports integrin alpha4-beta7 complex Research
Researchers studying integrin alpha4-beta7 complex-related genes often need to determine whether a candidate gene is causally involved in complex assembly, ligand binding, or downstream signaling. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models that answer these questions.
Contact EDITGENE today to design your custom CRISPR model for integrin alpha4-beta7 complex research.
Frequently Asked Questions About integrin alpha4-beta7 complex
What is the integrin alpha4-beta7 complex?
The integrin alpha4-beta7 complex (GO:0034669) is a heterodimeric cell-surface adhesion receptor composed of one alpha4 (ITGA4) subunit and one beta7 (ITGB7) subunit, defined as a cellular_component in QuickGO.
What genes are involved in the integrin alpha4-beta7 complex?
The core genes are ITGA4 and ITGB7, which encode the two subunits. Other key genes include MADCAM1 and VCAM1 (ligands), TGFB1 (regulator of ITGB7), and TLN1 and FERMT2 (activation adaptors).
What is the function of alpha4-beta7 integrin?
It functions as a gut-homing receptor that binds MAdCAM-1 and VCAM-1, mediating lymphocyte adhesion, arrest, and transendothelial migration into intestinal tissue.
Which diseases are associated with integrin alpha4-beta7?
It is associated with inflammatory bowel disease, IgA nephropathy, HIV-1 infection, and gastrointestinal CAR T-cell lymphoma.
How is the integrin alpha4-beta7 complex regulated?
It is regulated transcriptionally by TGF-beta1 through the ITGB7 promoter and by inflammatory cytokines such as IL-12, and functionally by inside-out signaling via talin and kindlin.
What is the role of alpha4-beta7 in HIV infection?
Alpha4-beta7 is a recognized HIV-1 attachment factor, and host proteins including integrins can be incorporated into the viral envelope, potentially facilitating viral entry.
How can I study the integrin alpha4-beta7 complex in the lab?
Common methods include flow cytometry, static and flow-based adhesion assays, transendothelial migration assays, multi-omics, imaging, and CRISPR knockout or knock-in models.
What is the ligand for alpha4-beta7 integrin?
The principal ligands are MAdCAM-1, expressed on gut mucosal endothelium, and VCAM-1, expressed on activated endothelium.
Is alpha4-beta7 a drug target?
Yes, the anti-alpha4-beta7 antibody vedolizumab is used clinically to treat inflammatory bowel disease by blocking lymphocyte gut homing.
What CRISPR models are available for alpha4-beta7 research?
Knockout of ITGA4 or ITGB7, point mutations in the beta7 cytoplasmic tail, fluorescent knock-in reporters, and overexpression cell lines are all available to study the complex.
Conclusion
The integrin alpha4-beta7 complex (GO:0034669) is a well-defined heterodimeric adhesion receptor that serves as the principal gut-homing molecule on lymphocytes. Its composition, ligand specificity, and regulation have been characterized in detail, and its clinical relevance is underscored by the success of anti-alpha4-beta7 therapeutics in inflammatory bowel disease. Beyond the gut, the complex is implicated in IgA nephropathy, HIV-1 attachment, and CAR T-cell biology, making it a versatile subject for both basic and translational research. For researchers, GO:0034669 offers a precise annotation target and a rich set of experimental models. CRISPR knockout, point mutation, knock-in, and overexpression approaches, combined with flow cytometry, adhesion assays, and multi-omics, provide a comprehensive toolkit to dissect the complex's function. As new links to disease emerge, the alpha4-beta7 integrin will remain a focal point for understanding leukocyte trafficking and mucosal immunity.
References
- 1. Chen PH et al.. 2021. Eosinophilic Gastritis/Gastroenteritis.. Curr Gastroenterol Rep 23(8):13 PMID: 34331146
- 2. Liu X et al.. 2026. Multi-omics analyses reveal the pathogenic role of terminal ileum-derived IgA(+)β7(+) cells in IgA nephropathy.. Kidney Int 109(4):780-795 PMID: 41571098
- 3. Wilen CB et al.. 2012. HIV: cell binding and entry.. Cold Spring Harb Perspect Med 2(8) PMID: 22908191
- 4. Pedrotti LP et al.. 2016. Systemic IL-12 burst expands intestinal T-lymphocyte subsets bearing the α₄ β₇ integrin in mice.. Eur J Immunol 46(1):70-80 PMID: 26464149
- 5. Hosoya H et al.. 2026. Long-term follow-up of gastrointestinal CAR T-cell lymphoma: homing, clonal expansion, and response to cyclosporine.. Blood 147(11):1191-1198 PMID: 41288531
- 6. Lim SP et al.. 1998. The beta7 integrin gene (Itgb-7) promoter is responsive to TGF-beta1: defining control regions.. Immunogenetics 48(3):184-95 PMID: 9683663
- 7. Omole TE et al.. 2025. Integrin α4β7 as a predictor of HIV acquisition: one thread in a complex tapestry.. J Clin Invest 135(15) PMID: 40759568
- 8. Burnie J et al.. 2019. The Incorporation of Host Proteins into the External HIV-1 Envelope.. Viruses 11(1) PMID: 30669528
