GO:0005615 obsolete extracellular space: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0005615 (obsolete extracellular space) is an obsolete cellular_component term that described the fluid-filled region outside the plasma membranes of cells in a multicellular organism.
• The term has been retired because 'extracellular space' is now represented by more precise ontology children such as extracellular vesicle, extracellular matrix, and extracellular region.
• The biological space it described is now studied mainly through extracellular vesicles (EVs), including exosomes, which carry proteins, lipids, and nucleic acids between cells.
• Exosome release can dispose of obsolete biomolecules and delay senescence, linking the extracellular space to aging and quality-control biology.
• EVs in this space mediate intercellular and even cross-species communication, and are implicated in cancer, neurodegeneration, and reproductive biology.
• Researchers study this compartment using EV isolation, proteomics, imaging, and CRISPR-based models of EV cargo and secretion genes.
Description
GO:0005615, officially named obsolete extracellular space, is a retired Gene Ontology cellular_component term that was defined as the part of a multicellular organism outside the cells proper, usually taken to be outside the plasma membranes and occupied by fluid. Although the term itself is obsolete, the biological compartment it described remains central to cell biology because it is the medium through which cells exchange signals, nutrients, and vesicles. The synonym intercellular space reflects its historical use for the fluid-filled gaps between cells in tissues. Modern ontology practice replaces this broad concept with more specific children such as extracellular vesicle, extracellular matrix, and extracellular region, which allow precise annotation of gene products. For researchers, understanding GO:0005615 is therefore a matter of understanding why the term was retired and how its successor terms are used in functional enrichment, proteomics, and disease studies. The extracellular space is not an empty gap; it is an active compartment populated by extracellular vesicles (EVs), including exosomes, microvesicles, and apoptotic bodies, that carry proteins, lipids, and RNA. Exosomes, for example, are released by many cell types and can transfer cargo to recipient cells, influencing processes as diverse as Wnt signaling, immune regulation, and neuronal function. Because the obsolete term captured this entire fluid-filled compartment, its literature overlaps heavily with EV biology, making it a useful entry point for understanding how the extracellular environment shapes physiology and disease.
obsolete extracellular space At A Glance
| GO ID | GO:0005615 |
|---|---|
| GO term | obsolete extracellular space |
| Ontology | cellular_component |
| Synonym | intercellular space |
| Definition | OBSOLETE. That part of a multicellular organism outside the cells proper, usually taken to be outside the plasma membranes, and occupied by fluid. |
| Status | Obsolete; replaced by more specific extracellular terms such as extracellular vesicle, extracellular matrix, and extracellular region. |
| Major function | Described the fluid-filled compartment outside cells where intercellular exchange and vesicle-mediated communication occur. |
| Related structures | Extracellular vesicles (exosomes, microvesicles), extracellular matrix, and extracellular fluid. |
| Research relevance | Central to EV biology, proteomics, intercellular signaling, aging, cancer, and neurodegeneration research. |
What Is GO:0005615?
In the QuickGO record, GO:0005615 is marked OBSOLETE and defined as the part of a multicellular organism outside the cells proper, usually taken to be outside the plasma membranes, and occupied by fluid. In plain terms, it described the watery, protein-rich space surrounding cells in a tissue, including the fluid between cells and the contents of that fluid. The term carried the synonym intercellular space and belonged to the cellular_component ontology aspect. Because the definition was broad and overlapped with newer, more precise terms, GO:0005615 was retired; current annotations use child terms such as extracellular vesicle, extracellular matrix, and extracellular region to describe specific extracellular structures and fluids.
Why Is obsolete extracellular space Important in Cell Biology?
Although GO:0005615 is obsolete, the compartment it described is essential for understanding how cells communicate and how extracellular material influences health and disease. Extracellular vesicles in this space carry bioactive cargo that can reprogram recipient cells, and their release is linked to disposal of obsolete biomolecules and delayed senescence. Because the term was used in thousands of annotations before retirement, researchers still encounter it in legacy datasets and must map it to current ontology children to interpret enrichment results correctly.
• The extracellular space is the site of EV-mediated intercellular communication, including exosome transfer of proteins and RNA.
• Exosome release can dispose of obsolete biomolecules and delay cellular senescence, linking the compartment to aging.
• EVs in this space participate in Wnt signaling and other developmental pathways.
• Extracellular vesicles are implicated in nervous system physiology and pathology, including neurodegeneration.
• The compartment is relevant to reproductive biology, including menstrual and endocrine-paracrine signaling.
• Proteomic studies of reticulocyte-derived exosomes reveal the cargo complexity of this space.
• Cross-species and cross-kingdom EV communication occurs in this compartment.
• Legacy annotations to GO:0005615 must be remapped to current extracellular terms for accurate enrichment analysis.
• EVs in the extracellular space are candidate biomarkers and therapeutic vehicles.
• Spatial and border-expansive regeneration studies highlight the extracellular environment as a regulator of tissue repair.
What Happens During obsolete extracellular space?
Release of extracellular vesicles into the space
In simple terms: Cells package molecular cargo into small bubbles and release them into the fluid outside the cell.
The extracellular space described by GO:0005615 is populated by extracellular vesicles (EVs), including exosomes, microvesicles, and apoptotic bodies, which are released from cells into the surrounding fluid. Exosome release is a regulated process that can dispose of obsolete biomolecules and delay senescence, indicating that the compartment serves as a disposal and communication route. EVs carry proteins, lipids, and nucleic acids that reflect the state of the donor cell.
Cargo sorting and packaging
In simple terms: Specific molecules are selected and packed into vesicles before they leave the cell.
Cargo sorting into EVs is selective and involves membrane trafficking machinery that determines which proteins and RNAs enter the vesicle. Proteomic analysis of human cord blood reticulocyte-derived exosomes has catalogued the protein cargo of these vesicles, showing that the extracellular space contains a complex and reproducible set of molecules. This sorting step is critical because it determines the functional impact of EVs on recipient cells.
Intercellular and cross-species communication
In simple terms: Vesicles released into the space can deliver messages to other cells, even across species.
EVs in the extracellular space can interact with recipient cells and transfer cargo, thereby mediating intercellular communication. Exosomes have been described as vehicles that go with Wnt, linking the extracellular compartment to developmental signaling. EVs are also on the border of species and kingdom intercommunication, indicating that the space is a hub for diverse signaling exchanges.
Physiological roles in the nervous system
In simple terms: In the brain, vesicles in the extracellular space help neurons and glia communicate.
Exosomes in the nervous system have physiological and pathological roles, including neuronal communication and clearance of proteins. The extracellular space of the nervous system is therefore an active compartment where EVs contribute to homeostasis and disease. This has implications for understanding neurodegeneration and for developing EV-based biomarkers.
Endocrine and paracrine control
In simple terms: The space between cells carries hormones and local signals that control tissue function.
The endocrine and paracrine control of menstruation involves signaling molecules that act in the extracellular space to coordinate tissue remodeling. This illustrates how the compartment described by GO:0005615 is central to reproductive physiology and intercellular coordination. Similar paracrine mechanisms operate in many tissues, underscoring the broad relevance of the extracellular space.
Key Genes Involved in GO:0005615 obsolete extracellular space
The following genes and proteins are representative of the extracellular space and EV biology that replaced GO:0005615 in modern annotation.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CD9 | Tetraspanin enriched on exosomes; contributes to EV biogenesis and cargo sorting | Common exosome marker used in EV isolation and characterization |
| CD63 | Tetraspanin marker of late endosomes and exosomes | Widely used to identify exosomes in the extracellular space |
| CD81 | Tetraspanin involved in EV formation and membrane organization | Marker for EV subpopulations and cell-cell communication studies |
| TSG101 | ESCRT-I component required for multivesicular body formation and exosome release | Functional studies of EV secretion and cargo sorting |
| ALIX | ESCRT-associated protein involved in exosome biogenesis | Mechanistic studies of EV release and cargo recruitment |
| RAB27A | Small GTPase regulating exosome secretion | Knockout models to test EV-dependent communication |
| RAB27B | Small GTPase involved in secretory vesicle trafficking | Studies of regulated exocytosis and EV release |
| SMPD2 | Sphingomyelin phosphodiesterase involved in ceramide-dependent EV formation | Investigations of lipid-dependent exosome biogenesis |
| SMPD3 | Neutral sphingomyelinase that promotes ceramide-rich EV budding | Models of EV biogenesis and senescence |
| WNT3A | Wnt ligand associated with exosomes | Studies of exosome-mediated Wnt signaling |
| WNT5A | Wnt ligand linked to exosomal transport | Research on EV-dependent developmental signaling |
| HBB | Hemoglobin subunit found in reticulocyte exosomes | Proteomic studies of red blood cell-derived EVs |
| HBA1 | Hemoglobin subunit in reticulocyte exosomes | Cargo analysis of erythroid EVs |
| GAPDH | Glycolytic enzyme commonly detected in EVs | Frequent EV proteomic marker and control |
| ACTB | Actin cytoskeleton protein present in EVs | EV proteomics and cytoskeleton-related cargo studies |
| HSPA8 | Heat shock protein involved in protein quality control and EV cargo | Studies of stress and EV-mediated disposal |
| ANXA2 | Annexin involved in membrane repair and EV release | Research on EV biogenesis and extracellular space dynamics |
| SDC1 | Syndecan-1 proteoglycan in the extracellular matrix and EV surface | Studies of extracellular matrix and EV interactions |
How Is obsolete extracellular space Regulated?
The extracellular space and its EV content are regulated at multiple levels. Exosome release can be modulated by cellular senescence programs, where disposal of obsolete biomolecules through EVs delays senescence. Rab GTPases such as RAB27A and RAB27B regulate the docking and fusion of multivesicular bodies with the plasma membrane, controlling how much EV cargo enters the extracellular space. Lipid metabolism, particularly ceramide generation by sphingomyelinases, influences EV budding and the composition of the extracellular compartment. In the nervous system, physiological and pathological states alter exosome release, affecting protein clearance and intercellular signaling. Endocrine and paracrine signals also shape the extracellular environment in reproductive tissues. Together, these mechanisms determine the molecular composition and functional capacity of the space formerly annotated as GO:0005615.
obsolete extracellular space and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| RAB27A | EV secretion and cancer progression | Knockout cell lines to measure EV release and recipient cell signaling |
| CD63 | Exosome marker in neurodegeneration | Tagged knock-in for live imaging of exosome trafficking |
| TSG101 | EV biogenesis in senescence | Knockout to test disposal of obsolete biomolecules |
| WNT5A | Exosome-mediated developmental signaling | Overexpression and EV transfer assays |
| HBB | Reticulocyte exosome cargo in blood disorders | Proteomic analysis of patient-derived EVs |
Cancer and EV-mediated communication
Extracellular vesicles in the space formerly described by GO:0005615 can transfer oncogenic signals between cells and influence the tumor microenvironment. Because EVs carry proteins and RNA, they are studied as mediators of cancer progression and as potential biomarkers. The obsolete term's successor terms are used to annotate genes involved in EV secretion and cargo in cancer models.
Neurodegeneration and exosome biology
Exosomes in the nervous system have both physiological and pathological roles, including the spread of misfolded proteins in neurodegenerative disease. The extracellular space is therefore a key compartment for understanding how pathological proteins move between neurons. EV-based biomarkers from this space are under investigation for neurological disorders.
Aging and senescence
Exosome release can delay senescence by disposing of obsolete biomolecules, linking the extracellular compartment to aging biology. This suggests that the space outside cells is not passive but actively contributes to cellular quality control. Research on senescence and EV cargo may reveal therapeutic opportunities.
Reproductive and endocrine disorders
The endocrine and paracrine control of menstruation depends on signaling within the extracellular space, and disruptions can contribute to reproductive disorders. Studying EVs and soluble factors in this compartment may clarify mechanisms of menstrual regulation and related pathologies. This highlights the clinical relevance of the space once annotated as GO:0005615.
From obsolete extracellular space-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does a gene regulate EV release into the extracellular space? | CRISPR knockout of candidate gene followed by EV quantification |
| Does a specific mutation alter EV cargo sorting? | Point-mutation knock-in in EV cargo proteins |
| Can a tagged EV protein be tracked in live cells? | Tagged knock-in of CD63 or CD9 |
| Does overexpression of a Wnt ligand increase exosomal Wnt? | Overexpression of WNT3A or WNT5A |
| Does loss of an ESCRT component block exosome biogenesis? | Knockout of TSG101 or ALIX |
| Does EV cargo change during senescence? | Senescence models with EV proteomics |
How to Study the obsolete extracellular space Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Ultracentrifugation | Physical isolation of EVs from extracellular fluid | Basic EV characterization |
| Nanoparticle tracking analysis | Size and concentration of EVs | Quality control of EV preparations |
| Western blot | Presence of EV markers such as CD9, CD63, CD81 | Confirmation of EV identity |
| Mass spectrometry proteomics | Protein cargo of EVs | Biomarker discovery and cargo mapping |
| Fluorescence imaging | EV release and uptake in live cells | Tracking intercellular communication |
| Wnt reporter assay | Exosome-mediated Wnt signaling | Developmental signaling studies |
| Senescence assays | EV-dependent disposal of obsolete biomolecules | Aging research |
| CRISPR knockout | Gene function in EV biogenesis | Mechanistic studies of the extracellular space |
Extracellular vesicle isolation and characterization
Studying the space formerly annotated as GO:0005615 typically begins with isolation of EVs from conditioned medium or body fluids using ultracentrifugation, size-exclusion chromatography, or affinity capture. Characterization by electron microscopy, nanoparticle tracking, and Western blotting for markers such as CD9, CD63, and CD81 confirms EV identity. These methods define the physical and molecular content of the extracellular compartment.
Proteomics of EV cargo
Mass spectrometry-based proteomics can catalogue the protein content of EVs, as demonstrated for human cord blood reticulocyte-derived exosomes. This approach reveals the complexity of the extracellular space and identifies candidate biomarkers. Comparative proteomics can also show how cargo changes with disease or genetic perturbation.
Imaging of EV release and uptake
Live-cell imaging with fluorescently tagged EV markers allows visualization of vesicle release into the extracellular space and uptake by recipient cells. Tagged knock-in models are particularly useful for tracking endogenous proteins. Imaging in nervous system models has clarified exosome dynamics in physiological and pathological states.
Functional assays for intercellular communication
EV transfer assays measure whether cargo from donor cells affects recipient cells, for example through Wnt signaling readouts. Such assays link the extracellular space to downstream cellular responses. Cross-species EV communication can also be tested in co-culture systems.
How CRISPR Can Be Used to Study GO:0005615 obsolete extracellular space
Knockout
CRISPR knockout of genes such as RAB27A, TSG101, or SMPD3 can test whether they are required for EV release into the extracellular space. Loss-of-function models help establish causality between a gene and EV-dependent phenotypes. Knockout studies of senescence-related EV disposal have shown that exosome release can delay senescence.
Point Mutation
Point-mutation knock-in can dissect specific residues required for EV cargo sorting or membrane fusion. Such models are useful when complete knockout is lethal or when domain-specific functions are being tested. They allow precise structure-function analysis of proteins acting in the extracellular space.
Knock-in
Tagged knock-in of EV markers such as CD63 or CD9 enables live tracking of vesicles as they enter the extracellular space. Knock-in of reporter genes can also be used to monitor signaling events mediated by EVs. These models preserve endogenous regulation and are valuable for imaging studies.
Overexpression
Overexpression of Wnt ligands such as WNT3A or WNT5A can increase exosomal Wnt and test downstream signaling in recipient cells. Overexpression models are also used to study how excess cargo affects EV composition and function. They complement knockout approaches by revealing gain-of-function phenotypes.
How EDITGENE Supports obsolete extracellular space Research
Researchers studying obsolete extracellular space-related genes often need to determine whether a candidate gene is causally involved in EV biogenesis, cargo sorting, or intercellular communication. Because GO:0005615 is obsolete, functional studies must target the specific successor processes and structures, such as extracellular vesicle release or matrix organization. EDITGENE provides the CRISPR tools and bioinformatics support needed to build such models efficiently and reproducibly.
Contact EDITGENE today to design your custom CRISPR model for obsolete extracellular space research.
Frequently Asked Questions About obsolete extracellular space
What is GO:0005615 obsolete extracellular space?
GO:0005615 is a retired Gene Ontology cellular_component term that described the fluid-filled part of a multicellular organism outside the cells proper, usually outside the plasma membranes. It is now obsolete and replaced by more specific terms such as extracellular vesicle and extracellular region.
Why is GO:0005615 obsolete?
The term was retired because its broad definition overlapped with newer, more precise extracellular terms that allow better annotation of gene products. Current practice uses child terms to describe specific extracellular structures and fluids.
What genes are involved in the extracellular space?
Genes encoding EV markers and machinery such as CD9, CD63, CD81, TSG101, ALIX, RAB27A, and SMPD3 are commonly studied in this compartment. Cargo proteins like HBB and HSPA8 have also been identified in EV proteomes.
How do exosomes relate to the obsolete extracellular space?
Exosomes are extracellular vesicles released into the space formerly described by GO:0005615, and they carry proteins, lipids, and RNA between cells. Exosome release can dispose of obsolete biomolecules and delay senescence.
What diseases are linked to the extracellular space?
EVs in this space have been implicated in cancer, neurodegeneration, aging, and reproductive disorders. They are also studied as biomarkers and therapeutic vehicles.
How can I study genes in the extracellular space using CRISPR?
CRISPR knockout, point mutation, knock-in, and overexpression can be used to test gene function in EV biogenesis and intercellular communication. Tagged knock-in of CD63 or CD9 enables live imaging of EVs.
What methods are used to analyze extracellular vesicles?
Common methods include ultracentrifugation, nanoparticle tracking analysis, Western blotting, proteomics, and fluorescence imaging. Functional assays such as Wnt reporter assays test EV-mediated signaling.
What is the difference between extracellular space and extracellular region?
Extracellular space was an obsolete broad term, while extracellular region is a current ontology term that encompasses specific extracellular structures and fluids. Researchers should use current terms for annotation and enrichment analysis.
Can exosomes cross species barriers?
Yes, exosomes are on the border of species and kingdom intercommunication, meaning they can mediate cross-species signaling. This has implications for host-microbe interactions and evolutionary biology.
What is the role of exosomes in the nervous system?
Exosomes in the nervous system have physiological and pathological roles, including neuronal communication and protein clearance. They are studied in neurodegeneration and as potential biomarkers.
Conclusion
GO:0005615 obsolete extracellular space is a retired ontology term, but the biological compartment it described remains a vibrant area of research. Extracellular vesicles, including exosomes, populate this space and mediate intercellular communication, cargo disposal, and disease processes. Researchers should map legacy annotations to current terms and use CRISPR models to dissect gene function in this compartment. EDITGENE offers the tools and expertise to support such studies from knockout to library screening.
References
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- 3. Schuh CMAP et al.. 2019. Exosomes on the border of species and kingdom intercommunication.. Transl Res 210:80-98 PMID: 30998903
- 4. Koles K et al.. 2012. Exosomes go with the Wnt.. Cell Logist 2(3):169-173 PMID: 23739155
- 5. Henriet P et al.. 2012. The endocrine and paracrine control of menstruation.. Mol Cell Endocrinol 358(2):197-207 PMID: 21820486
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- 7. Díaz-Varela M et al.. 2018. Proteomics study of human cord blood reticulocyte-derived exosomes.. Sci Rep 8(1):14046 PMID: 30232403
- 8. Yuyama K et al.. 2016. Physiological and pathological roles of exosomes in the nervous system.. Biomol Concepts 7(1):53-68 PMID: 26812803
