This website uses cookies to ensure you get the best experience on our website.
- Table of Contents
GJA1 / Gap junction alpha-1 protein · IHC design guide
Design Immunohistochemistry for GJA1
Plan chromogenic IHC on paraffin sections using heart muscle cardiomyocytes as a high-staining reference (HPA tissue IHC). Assess cytoplasmic and membranous staining while looking for GJA1 at intercalated discs between cardiomyocytes (HPA tissue IHC; UniProt).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
GJA1 Immunohistochemistry Experimental Design Guide
Expected localisation, validated protocols, controls and antibodies — the at-a-glance facts below, then the full design guide.
Must know before staining
| Expected localisation | Membranous and cytoplasmic in tissue IHC (HPA tissue IHC) | |
| Staining pattern | Most cell types: cytoplasmic and membranous staining (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen) | |
| Positive control | Adrenal gland+4 more · see all | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation consistent across sections. (standard IHC practice; not target-specific) | |
| Caveat | Cytoplasmic signal may accompany junctional staining (HPA tissue IHC; UniProt) | |
| Regulation | Expression regulation not specified (UniProt) | |
| Isoform / epitope | 0 annotated isoforms; epitope location matters (UniProt) |
Section 1
Recommended GJA1 IHC & IF Protocols
The catalog antibody’s IHC-P protocol is accompanied by published GJA1 IHC protocols for liver and goat skin sections (PMC12930822; PMC12464370).
| Sample | Tissue sections; selected-image fixative not specified (standard IHC workflow) |
| Fixation | Image fixative and duration unreported (datasheet M00599-1); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat-induced epitope retrieval in citrate buffer, pH 6.0, 20 min at 95–98 °C (standard rule: cytoplasmic / membrane antigen) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% normal serum of the secondary host, 30 min, room temperature (standard) |
| Primary antibody | Rabbit anti-GJA1, 1:200-1:1000 (datasheet M00599-1) |
| Primary incubation | Overnight at 4 °C (standard) |
| Detection | HRP-polymer secondary, DAB chromogen 5–10 min (standard) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | GJA1-positive staining in glandular cells of adrenal gland (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic and membranous expression in most cell types. No signal in the no-primary control. |
💡Decision noteStart with citrate pH 6.0 retrieval at 95–98 °C for 20 min (page antigen retrieval); a liver study used Tris-EDTA pH 9.0 (PMC12930822).
Section 2
What Is the Expected GJA1 Staining Pattern?
GJA1 is a four-pass membrane protein concentrated at gap junctions; UniProt also places it in the endoplasmic reticulum and at cardiomyocyte intercalated discs (UniProt P17302 topology and subcellular location). In paraffin-section IHC, expect membranous and some cytoplasmic staining in cell populations with documented expression, especially cardiomyocytes (HPA tissue IHC: High). HPA rates the tissue staining profile Enhanced, citing agreement between antibody staining and RNA expression (HPA tissue IHC: Enhanced).
| Distinct staining marks cardiomyocyte contacts, with some cytoplasmic signal. | This fits GJA1 at intercalated discs and gap junctions (UniProt P17302 subcellular location). Cardiomyocytes stain High in HPA tissue IHC (HPA: Heart muscle, High). Assess contact-associated signal alongside the overall tissue pattern; cytoplasmic staining alone does not exclude GJA1 because HPA reports cytoplasmic and membranous expression (HPA tissue IHC). |
| Strong staining is confined to nuclei, with little contact-associated or cytoplasmic signal. | Treat a nuclear-only IHC pattern as suspect and check controls before scoring it positive: HPA describes mainly cytoplasmic and membranous tissue staining (HPA tissue IHC). HPA reports nucleoplasmic localisation only as an uncertain additional finding in ICC-IF, which does not establish nuclear-only staining as the expected paraffin-section result (HPA subcellular). |
| Adipocytes or pancreatic exocrine glandular cells stain strongly. | These particular cell populations are Not detected in the HPA tissue images (HPA: Adipocytes; pancreatic exocrine glandular cells). Consider antibody cross-reactivity or endogenous detection activity, then compare a known-positive cell population and a no-primary control (general IHC practice). Do not label the entire adipose tissue or pancreas negative based on those cell-specific entries. |
| Brown signal spreads evenly across cells, stroma and empty areas without cell-contact detail. | This distribution is less convincing than junction-associated staining with a plausible cell pattern (UniProt P17302 subcellular location; HPA tissue IHC). Excess detection background or nonspecific binding is possible (general IHC practice). Check the no-primary control and inspect whether the signal tracks tissue structures before assigning a GJA1 score. |
| There is no signal in cardiomyocytes on a heart-muscle section. | The result conflicts with HPA's High cardiomyocyte staining and UniProt's intercalated-disc localisation (HPA: Heart muscle, High; UniProt P17302 subcellular location). Treat the run as inconclusive until section quality, antibody application and chromogenic detection are checked (general IHC practice); absence here alone does not establish lack of GJA1 expression. |
💡Expected GJA1 appearanceCall an IHC result positive when distinct membranous or junction-associated staining, with possible cytoplasmic signal, appears in a documented cell population such as High-staining cardiomyocytes (HPA tissue IHC; UniProt P17302 subcellular location); uniform haze or isolated strong nuclear staining is a suspect result, not a confident positive (general IHC practice; HPA subcellular: nucleoplasm uncertain).
| Membrane topology and antibody epitope | GJA1 has four transmembrane segments and cytoplasmic and extracellular regions (UniProt P17302 topology). If the antibody's epitope is known, use that information when interpreting accessible staining; the supplied record gives no catalog-antibody epitope, so it cannot predict a retrieval condition or staining strength. |
| Cell-specific tissue distribution | HPA reports High staining in cardiomyocytes, cervical squamous epithelial cells and placental cytotrophoblasts, but Not detected in adipocytes and pancreatic exocrine glandular cells (HPA tissue IHC). Choose and score the documented cell population, since one section can contain several cell types. |
| IHC validation scope | The HPA tissue profile is Enhanced; HPA035097 and CAB010753 each have Enhanced IHC validation, while HPA069245 has Supported IHC validation (HPA tissue IHC; HPA antibodies). Those ratings support interpretation of the reported IHC patterns, but do not establish the performance of an unspecified catalog antibody. |
| Subcellular interpretation across applications | HPA ICC-IF supports cell-junction localisation; its vesicle and nucleoplasm calls are uncertain (HPA subcellular). UniProt also lists the endoplasmic reticulum (UniProt P17302 subcellular location). These observations allow intracellular signal, but do not make every diffuse or nuclear IHC signal specific. |
| Situation | Likely cause | Next action |
|---|---|---|
| Known-positive heart muscle is blank. | A failed IHC run or inadequate detection is possible; cardiomyocytes are High in HPA tissue IHC (HPA: Heart muscle, High). | Check a known-positive section, reagent application and chromogenic detection; review retrieval against the chosen antibody's instructions (general IHC practice). No GJA1-specific retrieval condition is supplied. |
| Cardiomyocytes stain, but contact-associated detail is hard to see. | Cytoplasmic staining can coexist with membrane staining (HPA tissue IHC); a crowded or overly strong chromogenic signal can obscure fine localisation (general IHC practice). | Inspect well-preserved cell borders and intercalated-disc regions, then optimise antibody concentration or detection intensity using the positive control (general IHC practice; UniProt P17302 subcellular location). |
| Cells listed as Not detected stain strongly. | For adipocytes or pancreatic exocrine glandular cells, this conflicts with the cell-specific HPA observations; cross-reactivity or endogenous activity may contribute (HPA tissue IHC; general IHC practice). | Compare a no-primary control and a documented positive cell population before scoring; evaluate the stained cell type rather than assigning one result to the whole tissue (general IHC practice). |
| Diffuse brown haze covers the section. | Background from antibody or detection reagents is possible when staining lacks anatomical or junctional structure (general IHC practice; UniProt P17302 subcellular location). | Check the no-primary control, blocking and washes; adjust reagent concentration and detection time according to the IHC workflow (general IHC practice). Do not score uniform haze as GJA1. |
| Nuclei dominate the IHC signal. | HPA's nucleoplasmic ICC-IF call is uncertain, whereas its tissue IHC profile is cytoplasmic and membranous (HPA subcellular; HPA tissue IHC). | Check no-primary and positive controls, then re-evaluate cell borders and cytoplasm. Record nuclear-only staining as unresolved unless independently supported for this IHC assay (general IHC practice). |
| What should IF/ICC show? | HPA supports localisation at cell junctions and marks vesicles and nucleoplasm uncertain in ICC-IF (HPA subcellular). | Interpret junction-associated fluorescence as the stronger localisation evidence; treat isolated vesicular or nuclear signal cautiously (HPA subcellular). IF/ICC staining conditions belong to the separate IF/ICC guide. |
Experiment evidence
IHC & IF images showing GJA1 staining
M00599-1 · IHCHuman testis was stained with anti-Connexin 43 rabbit antibody
M00599-1 · IHCMouse spleen was stained with anti-Connexin 43 rabbit antibody
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000152661-GJA1/tissue/cerebral+cortex#imid_2948924
HPA · Parathyroid glandHuman Protein Atlas IHC, Parathyroid gland. Source: https://www.proteinatlas.org/ENSG00000152661-GJA1/tissue/parathyroid+gland#imid_2948807
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000152661-GJA1/tissue/colon#imid_2948842
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000152661-GJA1/tissue/liver#imid_2948851
HPA · ICC-IF AF22Human Protein Atlas immunofluorescence, AF22, antibody HPA047551; green = GJA1, blue = nucleus, red = microtubules.
HPA · ICC-IF AF22Human Protein Atlas immunofluorescence, AF22, antibody HPA047551; green = GJA1, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for GJA1 IHC & IF
🧪Run adrenal gland first: its glandular cells should stain (HPA: High in adrenal glandular cells). Use adipose tissue as the negative comparison because adipocytes are listed as Not detected (HPA: Not detected in adipocytes); on the adrenal slide, cells without junctional staining should show only background, but their absence of GJA1 is not established by the supplied HPA row (HPA: High in glandular cells; UniProt P17302 localization).
Positive control tissue: Adrenal gland (Glandular cells, HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show GJA1 in AF22, BJ [Human fibroblast], U2OS, KOLF2.1J, with annotated localisation: Vesicles (uncertain), Cell Junctions (supported) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control, a nonimmune isotype control matched to the primary antibody’s host and isotype, and a GJA1 knockout biological negative where available (standard IHC practice). For chromogenic adrenal sections, quench endogenous peroxidase and check whether tissue pigment could be mistaken for signal (standard IHC practice).
⚠️Feasibility: No target-specific fixation window, fixation effect, or antigen-retrieval dependency is reported in the supplied evidence; the selected M00599-1 human testis IHC caption does not state a fixative (selected-SKU caption: fixative unreported). Optimize retrieval on matched paraffin sections and score staining at cell junctions (standard IHC practice; UniProt P17302 localization). IF may help resolve junctional staining, but the supplied evidence does not establish whether IF or frozen sections are easier for this target; adrenal tissue pigment can complicate chromogenic interpretation (HPA: cell junctions supported in ICC-IF; standard IHC practice).
HPA tissue IHC evidence for GJA1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — High consistency between antibody staining and RNA expression data.). Rows are taken directly from the HPA tissue chart — click any row's HPA link to view the source.
Positive expression · recommended positive controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adrenal gland | Glandular cells | High | Protein (IHC) | HPA → |
| Cerebellum | Processes in granular layer | High | Protein (IHC) | HPA → |
| Cerebral cortex | Neuropil | High | Protein (IHC) | HPA → |
| Cervix | Squamous epithelial cells | High | Protein (IHC) | HPA → |
| Endometrium | Ciliated epithelial cells | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Appendix | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Bronchus | Respiratory epithelial cells | Not detected | Protein (IHC) | HPA → |
| Liver | Cholangiocytes | Not detected | Protein (IHC) | HPA → |
| Nasopharynx | Respiratory epithelial cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced GJA1 IHC Tips
Troubleshoot GJA1 chromogenic IHC by checking retrieval, staining at cell contacts, and controls before scoring expression (UniProt P17302 localisation; standard IHC practice).
What retrieval should I try when GJA1 staining is weak in paraffin sections?
Use citrate buffer at pH 6.0 for heat-induced retrieval at 95–98 °C for 20 min (page retrieval rule). Allow sections to cool in buffer, then compare staining with a known positive heart section processed in the same run (HPA: High in cardiomyocytes; standard IHC practice). Score signal at contacts between cardiomyocytes separately from diffuse cytoplasmic colour (UniProt P17302 localisation; standard IHC practice). If staining remains weak, test a longer retrieval time on a serial section while holding antibody dilution and detection constant (standard IHC practice). Excessive retrieval can damage section morphology, so inspect the counterstain and tissue edges before accepting a stronger signal (standard IHC practice).
Could fixation explain absent or diffuse GJA1 staining?
Target-specific fixation sensitivity is unknown from the supplied evidence; the catalog antibody’s human testis IHC caption does not state a fixative (SKU M00599-1 caption). Record fixative, fixation duration, processing history and section age for each specimen before comparing signal between cases (standard IHC practice). On matched serial sections, keep citrate retrieval at pH 6.0, 95–98 °C and 20 min while checking whether morphology and staining change together (page retrieval rule; standard IHC practice). Interpret punctate staining at cell contacts using an appropriate positive control, without assigning a fixation effect from tissue staining patterns alone (UniProt P17302 localisation; standard IHC practice).
Where should convincing GJA1 signal appear in chromogenic IHC?
Look first for staining along contacts between adjacent cells, especially at cardiomyocyte intercalated disks in heart sections (UniProt P17302 localisation). GJA1 is also reported at the cell membrane and endoplasmic reticulum, while tissue IHC shows cytoplasmic and membranous expression in most cell types (UniProt P17302 localisation; HPA: tissue IHC profile). Compare candidate puncta with cell boundaries on the counterstained section rather than calling every brown cytoplasmic granule a gap junction (standard IHC practice). If staining is exclusively nuclear or uniformly fills unrelated structures, review controls, morphology and detection background before interpreting it as GJA1 (HPA: cell junctions supported, nucleoplasm uncertain; standard IHC practice).
How do GJA1 topology and epitope uncertainty affect staining interpretation?
The record lists 0 annotated isoforms, but it does not identify the catalog antibody’s epitope (UniProt P17302 isoform record; supplied antibody evidence). GJA1 has 4 transmembrane segments, extracellular loops at residues 45–76 and 177–207, and a cytoplasmic tail at 229–382 (UniProt P17302 topology). Because modified residues include phosphorylation sites, epitope accessibility may differ across specimens, but this antibody’s sensitivity to those modifications is unknown (UniProt P17302 modified residues; supplied antibody evidence). Check the antibody’s epitope documentation before attributing a changed IHC pattern to isoforms, phosphorylation or loss of a particular protein region (standard IHC practice).
How should I compare GJA1 IHC with a multiplex IF experiment?
Treat IF as a separate assay and verify the antibody’s IF suitability before using chromogenic IHC staining to interpret fluorescent puncta (standard IHC/IF practice). Multiplex GJA1 with a marker identifying the expected cell type, such as cardiomyocytes when examining heart, and examine whether puncta follow contacts between those cells (UniProt P17302 localisation; standard IF practice). Choose a fluorophore channel with low measured tissue autofluorescence and include single-stain controls when separating multiplex signals (standard IF practice). Plan permeabilisation around the documented epitope: intracellular regions require access through the membrane, whereas extracellular-loop epitopes may be tested without permeabilisation (UniProt P17302 topology; standard IF practice).
What should I check when DAB obscures small GJA1 junctions?
Run a no-primary control to assess detection background, and inspect whether brown colour follows tissue edges or damaged areas (standard IHC practice). Block endogenous peroxidase before DAB detection, then check that wash steps remove unbound reagents without lifting the section (standard chromogenic IHC practice). Titrate the primary antibody and DAB development on matched sections so small contact-associated puncta remain distinguishable from diffuse colour (UniProt P17302 localisation; standard IHC practice). A negative reference population can help judge background: HPA reports GJA1 as not detected in adipocytes, although each specimen still needs its own morphology and control review (HPA: Not detected in adipocytes; standard IHC practice).
How should I score GJA1 IHC when junctional puncta vary between samples? ⚠ ANSWER MARKED FOR VERIFICATION
Define the scored compartment before counting, prioritising contact-associated staining when the question concerns gap junction localisation (UniProt P17302 localisation; standard IHC practice). Report the percentage of positive cells and an intensity score, or calculate an H-score from those values using the same thresholds across sections (standard IHC practice). For punctate junctional signal, measure positive junction density per mm² of viable tissue and normalise to the number of evaluable cells or cell contacts (standard IHC practice). Keep section thickness, retrieval, illumination and image analysis settings consistent, and exclude folds, edges and necrotic regions from the denominator (standard IHC practice).
How can I distinguish true GJA1 staining from artefact?
A plausible positive pattern follows cell contacts, including intercalated disks between adjacent cardiomyocytes, with morphology preserved on the counterstained section (UniProt P17302 localisation; standard IHC practice). Compare its distribution with the expected cell population; HPA reports high staining in cardiomyocytes and no detectable staining in adipocytes (HPA: High in cardiomyocytes; HPA: Not detected in adipocytes). Treat colour concentrated at section edges, folds or necrotic areas as suspect until it persists in well-preserved tissue (standard IHC practice). If a no-primary control also develops brown colour, review endogenous peroxidase blocking and DAB detection before calling the signal GJA1 (standard chromogenic IHC practice).
Boster reagents
Best GJA1 / Gap junction alpha-1 protein IHC Antibodies
The catalog lists GJA1 antibodies reactive with human, mouse, and rat samples, with paraffin-section IHC images, a rat-heart IF image, and a cell IF image (catalog; image captions).
Real IHC data
Anti-Connexin 43 Rabbit Monoclonal Antibody
Cat # M00599-1
Only M00599-1 renders as a card here (cards payload). Its IHC captions show human testis, mouse spleen, and rat spleen; IF is listed as an application, but no IF image is supplied for this SKU (M00599-1 catalog).
Which to pick: Choose M00599-1 for paraffin-section IHC across human, mouse, and rat: it is a rabbit monoclonal with IHC images for all three species (M00599-1 catalog; IHC captions). For IF in tissue, PA1026 has a rat-heart IF image; for IF/ICC in cells, A00599 has a U20S cell IF image, although IF is absent from its listed applications (PA1026 IF caption; A00599 IF caption and applications). The M00599-1 captions do not report a fixative (M00599-1 IHC captions).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P17302 (CXA1_HUMAN, Gap junction alpha-1 protein).
- Human Protein Atlas. GJA1 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. GJA1 subcellular location (ICC-IF): Mainly localized to the cell junctions and vesicles. In addition localized to the nucleoplasm..
- Human Protein Atlas. GJA1 antibody validation summary (4 antibodies).
- Ion channel gene signature for diagnosis and antifibrotic therapy in liver fibrosis. Journal of translational medicine 2026 — PMC12930822.
- Expressional and functional involvement of gap junctions in aqueous humor outflow into the ocular trabecular meshwork of the anterior chamber. Molecular vision 2019 — PMC6545340.
- Different Contacted Cell Types Contribute to Acquiring Different Properties in Brain Microglial Cells upon Intercellular Interaction. International journal of molecular sciences 2023 — PMC9861207.
- Phenotypic, transcriptomic, and genomic analyses reveal the spatiotemporal patterns and associated genes of coarse hair density in goats. Zoological research 2025 — PMC12464370.
- PubMed PMID:1696265 — UniProt-cited evidence.
- PubMed PMID:1646158 — UniProt-cited evidence.
- PubMed PMID:10581143 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for GJA1 (Gap junction alpha-1 protein). Expected localisation Membranous and cytoplasmic in tissue IHC (HPA tissue IHC). Antigen retrieval: Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen). Validated IHC antibody: M00599-1 at 1:200-1:1000 (the product's own IHC validation image is shown). Controls (HPA): positive Adrenal gland (Glandular cells); negative Adipose tissue. IHC workflow; specimen preparation unspecified. Protocol steps: 1. Sample: Tissue sections; selected-image fixative not specified (standard IHC workflow); 2. Fixation: Image fixative and duration unreported (datasheet M00599-1); verify before use.; 3. Sectioning: 4–5 µm sections on charged slides (standard); 4. Deparaffinisation: Xylene, graded ethanol series to water (standard); 5. Antigen retrieval: Heat-induced epitope retrieval in citrate buffer, pH 6.0 , 20 min at 95–98 °C…; 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% normal serum of the secondary host, 30 min , room temperature (standard); 8. Primary antibody: Rabbit anti-GJA1, 1:200-1:1000 (datasheet M00599-1); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: Keep fixation consistent across sections. (standard IHC practice; not target-specific); Caveat: Cytoplasmic signal may accompany junctional staining (HPA tissue IHC; UniProt); Isoform / epitope: 0 annotated isoforms; epitope location matters (UniProt); Regulation: Expression regulation not specified (UniProt). Evidence: UniProt P17302, HPA tissue IHC · Enhanced, HPA ICC-IF · Mainly localized to the cell junctions and vesicles. In addition…, Datasheet M00599-1, PMC12930822, PMC12464370. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/GJA1/immunohistochemistry-ihc-guide.