Recombinant Mouse Gap junction gamma-2 protein (Gjc2)
Description
Introduction to Recombinant Mouse Gap Junction Gamma-2 Protein
Gap junction gamma-2 protein, encoded by the Gjc2 gene in mice, is a member of the connexin family of transmembrane proteins. In mice, this protein is also referred to as Cx47, Gja12, or B230382L12Rik . The mouse Gjc2 gene is orthologous to the human GJC2 gene, which encodes the human connexin-47 protein .
Gjc2 belongs to the large family of connexin proteins that form intercellular channels known as gap junctions. These channels allow for the direct exchange of small molecules, ions, and nutrients between adjacent cells . Similar to other connexin proteins, Gjc2 consists of four transmembrane domains, two extracellular loops, and three cytoplasmic domains (one intracellular loop and the N- and C-terminal regions) .
Nomenclature and Classification
The nomenclature for Gjc2 has evolved over time, creating some confusion in the literature. Table 1 summarizes the various names and identifiers associated with mouse Gjc2 protein:
| Official Symbol | Alternate Names | Gene ID | UniProt ID | Paralog |
|---|---|---|---|---|
| Gjc2 | Cx47, Gja12, B230382L12Rik | MGI:2153060 | Q80XF7 (Mouse) | Gjc1 |
| Connexin-47, Gap junction gamma-2 protein, Gap junction alpha-12 protein |
Protein Structure and Domains
Mouse Gjc2 shares the typical connexin protein architecture with four transmembrane segments, two extracellular loops, one cytoplasmic loop, and cytoplasmic N- and C-terminal domains . This structure is critical for the protein's ability to form functional gap junction channels. Six connexin proteins assemble to form a connexon (hemichannel), and two connexons from adjacent cells dock to create a complete gap junction channel .
The mouse Gjc2 protein consists of 439 amino acids, similar to its human ortholog . The transmembrane domains are highly hydrophobic and anchor the protein in the cell membrane, while the extracellular loops contain conserved cysteine residues that are crucial for connexon docking .
Expression Pattern in Mouse Tissues
Studies using Cx47-deficient mice with enhanced green fluorescent protein (EGFP) reporter gene have provided valuable insights into the expression pattern of Gjc2 in mouse tissues . Unlike earlier assumptions based on mRNA studies, Gjc2 is predominantly expressed in:
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Oligodendrocytes in highly myelinated CNS tissues
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Some calcium-binding protein S100β subunit-positive cells (presumed astrocytes)
This expression pattern correlates with the protein's function in central nervous system myelination and establishing glial networks .
Gap Junction Formation and Intercellular Communication
The primary function of mouse Gjc2 is to form gap junction channels that facilitate intercellular communication . These channels create a direct conduit between the cytoplasm of adjacent cells, allowing for the diffusion of ions, metabolites, and small signaling molecules with molecular weights below 1 kDa .
In the central nervous system, Gjc2 forms both homotypic channels (composed of identical connexins) and heterotypic channels (composed of different connexin isoforms) . Particularly important is the interaction between Gjc2 in oligodendrocytes and Cx43 in astrocytes, forming heterotypic channels that are crucial for glial network function .
Role in Myelination
Mouse Gjc2 plays a critical role in central nervous system myelination . Studies with Gjc2-knockout mice have demonstrated that:
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Gjc2 is essential for normal oligodendrocyte function
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Loss of Gjc2 function results in myelin abnormalities
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Gjc2 works in concert with Cx32 (another connexin expressed in oligodendrocytes) to maintain myelin integrity
Functional studies reveal that in Gjc2-null mice, there is a more than 80% reduction in the number of cells participating in glial networks after biocytin injections into oligodendrocytes in the corpus callosum . This indicates the crucial role of Gjc2 in establishing and maintaining the interconnected glial network necessary for proper myelination.
Expression Systems
Recombinant mouse Gjc2 protein can be produced using various expression systems, each with its advantages depending on the intended application:
| Expression System | Advantages | Typical Purity | Application |
|---|---|---|---|
| Cell-Free Expression | Rapid production, avoids cellular toxicity | ≥85% by SDS-PAGE | Functional studies |
| E. coli | High yield, cost-effective | Variable | Structural studies |
| Mammalian Cells | Native folding and post-translational modifications | ≥85% by SDS-PAGE | Functional studies |
| Baculovirus | High expression of membrane proteins | ≥85% by SDS-PAGE | Structural and functional studies |
The most commonly used system for producing recombinant mouse Gjc2 is the cell-free expression system, which typically achieves a purity greater than or equal to 85% as determined by SDS-PAGE .
Purification and Characterization
Purification of recombinant mouse Gjc2 typically involves:
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Initial extraction using detergents suitable for membrane proteins
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Affinity chromatography (often using histidine tags)
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Size exclusion chromatography for final purification
The purified protein can be characterized using various techniques including mass spectrometry, circular dichroism spectroscopy, and functional assays to assess gap junction formation capabilities.
Mouse Models for Studying Gjc2 Function
Several mouse models have been developed to study Gjc2 function and its role in disease:
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Gjc2-null mice: Created by replacing the Gjc2 coding region with EGFP reporter gene, allowing visualization of cells normally expressing Gjc2
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Gjc2 point mutation models: Such as the Cx47M282T model which mimics human mutations associated with Pelizaeus-Merzbacher-like disease
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Double knockout models: Mice lacking both Cx47 and Cx32 show more severe phenotypes than single knockouts, demonstrating partial functional redundancy
These models have been instrumental in elucidating the functions of Gjc2 in vivo and its contributions to myelination disorders.
Key Research Findings
Studies using recombinant mouse Gjc2 and Gjc2-modified mice have revealed several important findings:
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Homozygous Gjc2-null mice are fertile and show no obvious morphological abnormalities but display impaired rotarod performance
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Electron microscopic investigation of Gjc2-null mice reveals abnormal myelin vacuolation of nerve fibers
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Mice expressing mutant Cx47M282T show a more than 80% reduction in oligodendrocyte coupling in glial networks
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Combined loss of Cx47 and Cx32 results in severe myelin abnormalities and early death, demonstrating the partial redundancy of these connexins
These findings highlight the importance of Gjc2 in maintaining myelin integrity and glial communication networks.
Mouse Models of Myelination Disorders
Recombinant mouse Gjc2 and genetically modified mouse models have been invaluable for studying human leukodystrophies and other myelination disorders:
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The Cx47M282T mouse model mimics the human Cx47M283T mutation that causes Pelizaeus-Merzbacher-like disease 1 (PMLD1)
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Studies with these mice have demonstrated that PMLD1 can result from both loss of Cx47 function and Cx47 dysfunction
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Homozygous Cx47M282T mice deprived of Cx32 showed severe myelin abnormalities and died within the first four months after birth, mimicking the severity of human PMLD1
These models provide platforms for testing potential therapeutic approaches for myelination disorders.
Comparative Analysis with Human GJC2
Research comparing mouse Gjc2 with human GJC2 has revealed important insights:
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Mouse Gjc2 shares high sequence homology with human GJC2, making mouse models relevant for studying human disease
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Similar disease mechanisms operate in both species, with mutations causing either loss of function or dysfunction of the protein
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The conserved domains critical for gap junction formation and function are similar between species
This conservation makes recombinant mouse Gjc2 a valuable tool for studying human myelination disorders.
Emerging Technologies and Approaches
Several advanced technologies are being applied to further understand Gjc2 function:
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CRISPR-Cas9 gene editing for creating more precise mouse models
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High-resolution imaging techniques to visualize gap junction dynamics in live tissues
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Single-cell transcriptomics to better understand the role of Gjc2 in different cell populations
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Improved production methods for obtaining higher yields and purity of recombinant protein
Therapeutic Potential
Research on recombinant mouse Gjc2 has implications for developing potential therapeutics:
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Small molecules that can enhance gap junction communication might ameliorate symptoms in myelination disorders
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Gene therapy approaches to correct Gjc2 mutations show promise in preclinical studies
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Understanding the interaction between different connexins could lead to therapeutic strategies targeting compensatory mechanisms
The continued study of recombinant mouse Gjc2 will likely contribute to the development of novel treatments for leukodystrophies and other myelination disorders.
Product Specs
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Note: All protein shipments are standardly packaged with blue ice packs. If dry ice packaging is required, please notify us in advance, as additional fees will apply.
Target Background
- Research suggests that Connexin47 is involved in the reversal of acute increases in serum triglycerides. Additionally, serum lipid levels in mice on a standard diet, but not a high-cholesterol diet, are influenced by Connexin47 expression. Furthermore, Connexin47 deficiency tends to increase plaque size while decreasing macrophage content in diet-induced atherosclerotic plaques. These studies show that Cx47-deficient mice do not display overt lymphatic phenotypes. PMID: 28732089
- Data indicates that the segregation of Foxc2 and NFATc1 transcription factors is closely associated with the highly polarized expression of connexins Cx37, Cx43, and Cx47. PMID: 26953188
- This study revealed alterations in Connexin47 expression following neural precursor cell transplantation in experimental autoimmune encephalomyelitis. PMID: 25914045
- This study demonstrated the functional roles of both connexins Cx30 and Cx47 in interastrocytic, interoligodendrocytic, and panglial coupling. The study highlights the essential roles of both connexins in maintaining myelin. PMID: 22649229
- PMLD1 (Pelizaeus-Merzbacher-like disease 1) arises from the loss of Cx47 channel function, resulting in impaired panglial coupling in white matter tissue. PMID: 21750683
- Research has investigated oligodendrocyte-astrocyte gap junction coupling in Cx32 or Cx47 knockout mice. In the neocortex, oligodendrocytes appear to be directly and exclusively coupled to astrocytes, and Cx47, but not Cx32, is required for O:A coupling. PMID: 21396451
- Oligodendrocytes in white matter form a functional syncytium predominantly among each other, dependent on Cx47 and Cx32 expression. Astrocytic connexins expression can further enhance the size of this network. PMID: 20468052
- Cx47-deficient mice exhibited vacuolation of nerve fibers at the site of the optic nerve, where axons are initially contacted by oligodendrocytes and myelination commences. Mice lacking both Cx32 and Cx47 developed action tremor and died approximately 51 days after birth. PMID: 12805295
- Mice lacking either Cx47 or Cx32 are viable. However, mice lacking both connexins die by postnatal week 6 due to abnormalities in CNS myelin sheaths, vacuolation, enlarged periaxonal collars, oligodendrocyte cell death, and axonal loss. PMID: 12843301
- All oligodendrocytes appear to express Cx47, predominantly localized to their perikarya. PMID: 15293232
- Research has demonstrated the presence of MUPP1 at O/A gap junctions and the Cx47-dependent targeting of connexins to the plasma membranes of oligodendrocyte somata. PMID: 18973575
Q&A
How does mouse Gjc2 compare to human GJC2?
Mouse Gjc2 shares significant homology with human GJC2, though with some key differences:
While both proteins serve similar functions in their respective species, understanding the differences is crucial for translating mouse model findings to human applications. Researchers should note that disease-causing mutations may have different effects between species.
What are the optimal storage conditions for recombinant mouse Gjc2?
For optimal stability and activity retention of recombinant mouse Gjc2 protein:
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Aliquoting is necessary for multiple use to avoid repeated freeze-thaw cycles which can denature the protein .
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For long-term storage, reconstituted protein should be supplemented with 5-50% glycerol (final concentration) and stored at -20°C/-80°C .
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The default recommended final glycerol concentration is 50% .
Researchers should record storage conditions and duration in their experimental protocols as these factors can significantly impact protein activity and experimental reproducibility.
What experimental approaches are most effective for studying Gjc2-mediated gap junction formation?
When studying Gjc2-mediated gap junction formation, consider these methodological approaches:
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Dye Transfer Assays: Implement fluorescent dye transfer experiments between cells expressing recombinant Gjc2 to quantify gap junction communication efficiency.
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Electrophysiological Recordings: Use dual patch-clamp techniques to measure electrical coupling between adjacent cells expressing Gjc2. This approach allows real-time assessment of gap junction functionality.
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Proximity Ligation Assays: Employ this technique to detect and visualize Gjc2 protein interactions with other connexins or associated proteins within a 40 nm radius.
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FRAP Analysis: Fluorescence Recovery After Photobleaching can measure the dynamics of gap junction assembly and communication by tracking labeled molecules through Gjc2 channels.
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Co-immunoprecipitation Studies: Identify interaction partners of Gjc2 using tagged recombinant protein. Based on the search results, Gjc2 interacts with proteins like Ybx3 .
When designing these experiments, use appropriate controls including cells expressing known non-functional Gjc2 mutants. Oligodendrocyte cell lines provide particularly relevant models as Gjc2 plays key roles in myelination processes in the central nervous system .
How can researchers effectively model Gjc2-related human diseases in experimental systems?
To model human diseases associated with GJC2 mutations using mouse Gjc2:
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Selection of Appropriate Mutations: Choose mutations that correspond to human disease variants. For example, mutations analogous to those causing Hypomyelinating Leukodystrophy 2 (HLD2), such as the c.760G>A (p.Val254Met) mutation identified in human patients .
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Expression Systems:
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For cellular studies: Express wild-type and mutant forms of recombinant mouse Gjc2 in oligodendrocyte cell lines
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For in vivo studies: Develop knock-in mouse models carrying specific Gjc2 mutations
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Functional Assessments:
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Comparative Analysis Framework:
| Parameter | Wild-Type Gjc2 | Disease-Associated Mutant |
|---|---|---|
| Protein Localization | Membrane | Often mislocalized |
| Gap Junction Formation | Normal assemblies | Disrupted architecture |
| Intercellular Communication | Efficient | Impaired |
| Myelination Capacity | Normal | Reduced/Aberrant |
| Interaction with Partner Proteins | Standard binding profile | Altered interactions |
Remember that mouse models may not perfectly recapitulate human pathology, so findings should be validated using human cells or tissue samples when possible.
What are the key considerations when optimizing expression and purification of recombinant mouse Gjc2?
Optimizing expression and purification of recombinant mouse Gjc2 requires addressing several technical challenges:
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Expression System Selection:
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Solubility Enhancement Strategies:
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Purification Protocol Optimization:
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Quality Control Metrics:
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Reconstitution Protocol:
These considerations help ensure consistent production of high-quality recombinant mouse Gjc2 for reliable experimental outcomes.
How can recombinant mouse Gjc2 be used to study oligodendrocyte-astrocyte gap junctions?
Recombinant mouse Gjc2 provides valuable tools for investigating oligodendrocyte-astrocyte gap junctions:
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Co-culture Systems:
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Establish co-cultures of oligodendrocytes expressing fluorescently tagged recombinant Gjc2 with astrocytes expressing partner connexins
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Monitor gap junction plaque formation at contact points using live-cell imaging
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Functional Communication Assays:
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Implement scrape loading/dye transfer assays using Lucifer Yellow or neurobiotin
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Quantify intercellular calcium wave propagation following focal stimulation
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Measure electrical coupling using dual patch-clamp recordings
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Heterologous Expression Studies:
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Express mouse Gjc2 in communication-deficient cell lines along with astrocytic connexins
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Assess compatibility and functional properties of heterotypic channels
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Introduce disease-associated mutations to determine effects on heterocellular coupling
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Analytical Approaches:
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Use FRET-based proximity assays to measure Gjc2 interactions with astrocytic connexins
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Apply super-resolution microscopy to characterize gap junction plaque architecture
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Employ freeze-fracture electron microscopy to visualize connexon arrangements
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Correlation with Myelination Processes:
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Monitor changes in gap junction coupling relative to myelination status
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Investigate how disruption of Gjc2-mediated coupling affects myelin maintenance
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Examine calcium transients through these gap junctions during myelination
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These approaches leverage recombinant mouse Gjc2 to illuminate the critical role of oligodendrocyte-astrocyte gap junctions in central nervous system function and myelination processes, which are disrupted in leukodystrophies and other myelin disorders .
What controls should be included when working with recombinant mouse Gjc2 in functional studies?
Rigorous controls are essential for ensuring valid and reproducible results when working with recombinant mouse Gjc2:
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Protein Quality Controls:
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Expression Controls:
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Empty vector transfections in cellular systems
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Non-gap junction forming membrane protein expression (negative control)
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Known functional connexin expression (positive control)
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Quantitative assessment of expression levels via Western blot
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Functional Assays Controls:
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Gap junction blockers (e.g., carbenoxolone, octanol) to confirm channel-dependent effects
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Non-permeable dye controls in transfer assays
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Calcium-free conditions in calcium wave propagation studies
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Untransfected cells as baseline controls
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Mutation Controls:
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Conservative amino acid substitutions at non-critical sites
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Known function-ablating mutations as negative controls
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Rescue experiments with wild-type protein
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Specificity Controls:
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Antibody controls: Isotype controls, pre-absorption controls
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Gene knockdown/knockout systems to verify specificity of antibody detection
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Comparing recombinant mouse Gjc2 with other connexin family members
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What are the recommended approaches for studying Gjc2 involvement in mouse models of leukodystrophy?
To investigate Gjc2's role in leukodystrophy using mouse models, researchers should consider these methodological approaches:
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Model Selection and Validation:
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Structural and Functional Analysis:
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Perform MRI and DTI imaging to quantify myelination defects in vivo
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Use electron microscopy to evaluate myelin ultrastructure
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Conduct electrophysiological assessments of nerve conduction velocity
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Analyze oligodendrocyte maturation through developmental time points
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Molecular Characterization:
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Therapeutic Intervention Studies:
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Test compounds that enhance gap junction communication
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Evaluate oligodendrocyte-targeted gene therapy approaches
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Assess cell-based therapies using oligodendrocyte precursors
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Measure outcomes using standardized myelin quantification techniques
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Data Collection Framework:
| Assessment Type | Parameters | Time Points | Analysis Method |
|---|---|---|---|
| Functional | Motor skills, coordination | 2, 4, 6, 12 months | Standardized tests |
| Imaging | Myelin content, brain volume | 1, 3, 6, 12 months | MRI quantification |
| Biochemical | Gjc2 expression, modification | Multiple developmental stages | Western blot, mass spec |
| Ultrastructural | Myelin thickness, periodicity | Key developmental points | EM morphometry |
| Molecular | Interacting partners, pathways | Pre- and post-symptom onset | Co-IP, proteomics |
These approaches provide comprehensive insights into how Gjc2 mutations lead to myelination defects and potential therapeutic strategies for leukodystrophies like Pelizaeus-Merzbacher-like disease .
How can researchers address solubility issues with recombinant mouse Gjc2?
As a transmembrane protein with four membrane-spanning domains , Gjc2 presents significant solubility challenges. Here are methodological approaches to overcome these obstacles:
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Optimization of Expression Constructs:
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Expression System Selection:
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Buffer Optimization Protocol:
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Purification Strategy Modifications:
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Implement on-column refolding for proteins expressed in inclusion bodies
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Use size exclusion chromatography to remove aggregates
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Consider detergent exchange during purification
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Explore amphipol or nanodisc reconstitution for enhanced stability
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Storage and Handling Protocols:
Successful production of soluble, functional recombinant mouse Gjc2 enables more reliable downstream applications and increases experimental reproducibility across different research groups.
What strategies can researchers use to differentiate between endogenous and recombinant Gjc2 in experimental systems?
Distinguishing between endogenous and recombinant Gjc2 is crucial for proper data interpretation. These methodological approaches provide clear differentiation:
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Epitope Tagging Strategies:
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Differential Expression Analysis:
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Design recombinant constructs with species variations if using cross-species systems
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Develop antibodies targeting species-specific epitopes
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Use quantitative PCR with primers specific to recombinant versus endogenous sequences
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Implement western blotting to distinguish size differences due to tags
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Functional Marking Approaches:
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Express fluorescently tagged Gjc2 for live visualization
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Utilize photoconvertible fluorescent protein fusions for pulse-chase studies
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Introduce specific mutations that alter electrophysiological properties
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Develop biorthogonal labeling strategies using unnatural amino acids
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Knockout/Knockdown Background Systems:
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Establish cell lines with CRISPR/Cas9-mediated Gjc2 knockout
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Use siRNA to reduce endogenous expression before introducing recombinant protein
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Rescue studies in Gjc2-null backgrounds provide cleaner systems for recombinant protein analysis
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Advanced Analytical Approaches:
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Employ mass spectrometry to differentiate tagged from untagged protein
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Use targeted proteomics with isotope-labeled standards for quantification
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Implement proximity labeling to map unique interaction landscapes
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These strategies ensure accurate attribution of observed phenotypes and molecular interactions to either endogenous or recombinant Gjc2 in experimental systems.
What emerging technologies show promise for advancing Gjc2 research?
Several cutting-edge technologies offer new avenues for understanding Gjc2 function and disease mechanisms:
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Advanced Imaging Technologies:
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Super-resolution microscopy for visualizing gap junction plaque architecture
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Live-cell CLEM (Correlative Light and Electron Microscopy) to connect Gjc2 dynamics with ultrastructure
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Expansion microscopy for detailed analysis of Gjc2 localization in myelin
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Functional Genomics Approaches:
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CRISPR/Cas9 screens to identify novel regulators of Gjc2 function
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Single-cell transcriptomics to map Gjc2 expression patterns in heterogeneous cell populations
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Spatial transcriptomics to correlate Gjc2 expression with anatomical features
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Structural Biology Innovations:
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Cryo-EM for resolving the structure of complete Gjc2 gap junction channels
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Hydrogen-deuterium exchange mass spectrometry to map conformational dynamics
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In-cell NMR to analyze Gjc2 behavior in native environments
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Biosensor Development:
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FRET-based sensors to monitor Gjc2 channel opening in real time
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Genetically encoded voltage indicators to assess electrical coupling
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Metabolite sensors to track small molecule transfer through Gjc2 channels
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Therapeutic Development Platforms:
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High-throughput screening systems for identifying Gjc2 function modulators
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AAV-based gene therapy approaches for Gjc2-related disorders
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Antisense oligonucleotides for modulating Gjc2 expression
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These emerging technologies will help address current knowledge gaps regarding Gjc2's role in myelination disorders and potentially lead to therapeutic strategies for conditions like Hypomyelinating Leukodystrophy 2 and Spastic Paraplegia 44 .
How might understanding Gjc2 function contribute to therapeutic strategies for myelination disorders?
Elucidating Gjc2 function presents several promising therapeutic avenues for myelination disorders:
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Gene Therapy Approaches:
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AAV-mediated delivery of functional Gjc2 to oligodendrocytes
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CRISPR-based correction of disease-causing mutations
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Antisense oligonucleotides to modulate splicing in certain mutations
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Evaluation of gene dosage effects for optimizing therapeutic outcomes
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Small Molecule Development:
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Cell-Based Therapies:
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Oligodendrocyte precursor cell transplantation with corrected Gjc2
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Engineered stem cell-derived oligodendrocytes for myelination
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Combined approaches targeting both neurons and glia
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Assessment using comprehensive functional readouts
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Pathway-Based Interventions:
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Biomarker Development for Clinical Trials:
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Noninvasive imaging markers of myelination status
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Functional connectivity measures correlating with Gjc2 activity
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Patient stratification based on specific mutations
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These therapeutic strategies could address conditions associated with GJC2 mutations, including Hypomyelinating Leukodystrophy 2, Spastic Paraplegia 44, and Lymphedema , potentially transforming treatment approaches for these currently intractable disorders.
