This website uses cookies to ensure you get the best experience on our website.
- Table of Contents
CNN1 / Calponin-1 · IHC design guide
Design Immunohistochemistry for CNN1
Plan chromogenic CNN1 IHC on paraffin sections using smooth muscle cells as a positive reference (HPA tissue IHC). Evaluate cytoplasmic staining by cell type, with breast myoepithelial cells also expected to stain (HPA tissue IHC).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CNN1 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 | Cytoplasmic in smooth muscle and myoepithelial cells (HPA tissue IHC) | |
| Staining pattern | Selective cytoplasmic staining in smooth muscle and myoepithelial cells (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6 HIER, heat-mediated (datasheet PA2224) | |
| Positive control | Endometrium+2 more · see all | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep paraffin-section fixation consistent (standard IHC practice; not target-specific); effects on CNN1 staining are unclear. | |
| Caveat | Myoepithelial cells can also stain in breast tissue (HPA tissue IHC) | |
| Regulation | Enriched in smooth muscle (UniProt) | |
| Isoform / epitope | 2 isoforms; epitope differences are unspecified (UniProt) |
Section 1
Recommended CNN1 IHC & IF Protocols
Compare the catalog antibody’s IHC-P protocol (datasheet PA2224) with 2 published CNN1 IHC methods (PMC13221474; PMC5617412).
| Sample | Tissue sections; selected-image fixative not specified (standard IHC workflow) |
| Fixation | Image fixative and duration unreported (datasheet PA2224); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat retrieval: Citrate pH 6, 20 min (datasheet PA2224) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet PA2224) |
| Primary antibody | Rabbit anti-CNN1, 0.5-1μg/ml (datasheet PA2224) |
| Primary incubation | Overnight at 4 °C (datasheet PA2224) |
| Detection | Streptavidin-biotin complex (SABC), DAB chromogen (datasheet PA2224) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | CNN1-positive staining in smooth muscle cells of endometrium (HPA tissue IHC: High). HPA tissue profile: Highly selective cytoplasmic expression in smooth muscle and myoepithelial cells. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated citrate retrieval at pH 6 for the catalog antibody (datasheet PA2224). The published methods do not specify a retrieval buffer (PMC13221474; PMC5617412).
Section 2
What Is the Expected CNN1 Staining Pattern?
CNN1 should appear as cytoplasmic staining in smooth muscle cells and breast myoepithelial cells (HPA tissue IHC: highly selective cytoplasmic expression). HPA rates its tissue IHC profile Enhanced, with high consistency between staining and RNA expression (HPA tissue IHC: Enhanced). CNN1 is associated with thin filaments and has no transmembrane segment (UniProt P51911: function and topology).
| Strong cytoplasmic signal in smooth muscle cells, including those in endometrium or smooth muscle tissue (HPA tissue IHC: High). | This fits the expected IHC pattern. Judge the signal in the identified cells, since other cells in the same section need not stain (HPA tissue IHC: highly selective cytoplasmic expression). |
| Predominantly nuclear or membranous signal, with little cytoplasmic staining (HPA tissue IHC: expected cytoplasmic pattern). | Treat this as discordant with the reported tissue pattern, not as evidence of a new CNN1 compartment (HPA tissue IHC: cytoplasmic; UniProt P51911: no transmembrane segment). Check staining controls and section morphology (general IHC practice). |
| Signal in adipocytes or respiratory epithelial cells, or widespread staining of unrelated cells (HPA tissue IHC: Not detected in those cell types). | Consider cross-reactivity or endogenous detection activity, especially if the expected smooth muscle pattern is unclear (general IHC practice). The HPA negatives apply to the named cell types; they do not make every cell in those tissues negative (HPA tissue IHC: cell-level observations). |
| Diffuse colour across cells and extracellular areas, obscuring cell boundaries (general IHC practice). | This is background until a discrete cytoplasmic smooth muscle pattern can be resolved (HPA tissue IHC: selective cytoplasmic pattern). Review controls, blocking, washes and detection conditions (general IHC practice). |
| No signal in identifiable smooth muscle cells of a known-positive section (HPA tissue IHC: High in smooth muscle cells). | An uninterpretable assay is more likely than a biological negative if the positive control also fails (general IHC practice). Check the antibody, retrieval and detection steps against the assay instructions (general IHC practice). |
💡Expected CNN1 appearanceCall positive when smooth muscle cells show strong cytoplasmic staining, with possible moderate cytoplasmic breast myoepithelial staining; isolated nuclear or broad unrelated-cell staining is discordant (HPA tissue IHC: High, Medium and selective cytoplasmic profile).
| Cell identity and tissue context (HPA tissue IHC: cell-level observations). | Endometrial and smooth muscle cells are reported High, while breast myoepithelial cells are Medium (HPA tissue IHC). Score the relevant cells rather than the whole tissue (general IHC practice). |
| Antibody validation (HPA antibodies: HPA014263 and CAB000007). | Both listed antibodies have Enhanced IHC status (HPA antibodies: IHC Enhanced). That supports the reported pattern but does not establish that every reagent or run will perform alike (general IHC practice). |
| IF/ICC Q: Where should fluorescence localise? (HPA ICC-IF: subcellular profile). | A: HPA reports actin filaments as the approved main location (HPA ICC-IF). This guides IF interpretation; the paraffin IHC tissue profile reports cytoplasmic staining (HPA tissue IHC). |
| Isoforms and epitope coverage (UniProt P51911: isoforms 1 and 2). | Two isoforms are listed, but these sources do not establish which isoforms a given antibody detects (UniProt P51911: isoforms; HPA antibodies: validation summary). Avoid assigning an isoform from staining alone. |
| Processing and topology (UniProt P51911: chain 1–297, no signal peptide or transmembrane segment). | The record lists no signal peptide or propeptide (UniProt P51911: processing). These annotations give no basis here for predicting secreted or membrane staining, or a fixation-specific effect. |
| Situation | Likely cause | Next action |
|---|---|---|
| Positive control smooth muscle is blank (HPA tissue IHC: High in smooth muscle cells). | The run may have failed; a blank control cannot establish biological absence (general IHC practice). | Verify tissue identity and controls, then check retrieval, antibody dilution and detection against the chosen assay instructions (general IHC practice). |
| Breast myoepithelial cells stain more weakly than smooth muscle (HPA tissue IHC: Medium versus High). | That relative difference is consistent with the reported cell-level staining (HPA tissue IHC: breast myoepithelial Medium; smooth muscle High). | Compare equivalent cells and controls before changing assay conditions solely to equalise intensity (general IHC practice). |
| Nuclei dominate the signal (HPA tissue IHC: expected cytoplasmic staining). | The compartment disagrees with the reported IHC pattern (HPA tissue IHC: cytoplasmic). | Inspect counterstain and negative controls, then reassess antibody and detection specificity (general IHC practice). |
| Adipocytes or respiratory epithelial cells stain strongly (HPA tissue IHC: Not detected). | Cross-reactivity or endogenous detection activity is possible (general IHC practice). | Compare a negative control and the expected smooth muscle pattern in the same run; review detection blocking as appropriate (general IHC practice). |
| Colour is diffuse and cell boundaries are hard to read (general IHC practice). | Background or excessive detection signal may obscure localisation (general IHC practice). | Review blocking, washes, development time and controls; score only clearly localised cellular signal (general IHC practice). |
| A vessel-associated signal is difficult to assign to a cell type (general IHC practice). | CNN1 is reported in smooth muscle, while HPA reports endothelial cells in cerebral cortex as Not detected (UniProt P51911: tissue specificity; HPA tissue IHC). | Use section morphology and the counterstain to identify the stained cells before recording a CNN1-positive population (general IHC practice). |
Experiment evidence
IHC & IF images showing CNN1 staining
PA2224 · IHCAnti-Calponin antibody, PA2224, IHC(P) IHC(P): Human Placenta Tissue
PA2224 · IHCIHC analysis of Calponin using anti-Calponin antibody (PA2224). Calponin was detected in paraffin-embedded section of mouse spleen tissue. H
M08065-1 · IHCIHC analysis of Calponin using anti-Calponin antibody (M08065-1). Calponin was detected in a paraffin-embedded section of human appendicitis
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000130176-CNN1/tissue/cerebral+cortex#imid_3637220
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000130176-CNN1/tissue/colon#imid_3637154
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000130176-CNN1/tissue/liver#imid_3637147
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000130176-CNN1/tissue/kidney#imid_3637156
![HPA ICC-IF BJ [Human fibroblast] — CNN1 (HPA014263)](https://images.proteinatlas.org/14263/1446_H4_3_blue_red_green.jpg)
HPA · ICC-IF BJ [Human fibroblast]Human Protein Atlas immunofluorescence, BJ [Human fibroblast], antibody HPA014263; green = CNN1, blue = nucleus, red = microtubules.
![HPA ICC-IF BJ [Human fibroblast] — CNN1 (HPA014263)](https://images.proteinatlas.org/14263/1446_H4_6_blue_red_green.jpg)
HPA · ICC-IF BJ [Human fibroblast]Human Protein Atlas immunofluorescence, BJ [Human fibroblast], antibody HPA014263; green = CNN1, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CNN1 IHC & IF
🧪Run endometrium first: its smooth muscle cells should stain strongly (HPA: High in endometrial smooth muscle cells). Use adipose tissue as the negative comparator, scoring adipocytes rather than the entire section (HPA: Not detected in adipocytes); non-smooth-muscle cells on the positive slide should lack specific staining (UniProt P51911: smooth-muscle tissue specificity).
Positive control tissue: Endometrium (Smooth muscle cells, HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show CNN1 in BJ [Human fibroblast], CACO-2, U2OS, with annotated localisation: Actin filaments (approved) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control and a host-species-matched isotype control for a monoclonal antibody, or matched normal immunoglobulin for a polyclonal antibody (standard IHC practice). A CNN1 knockout specimen provides a biological negative; quench endogenous peroxidase for chromogenic detection and check endogenous biotin if using avidin–biotin detection (standard IHC practice).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported in the supplied evidence, and the PA2224 paraffin-section placenta caption does not report a fixative (PA2224 IHC(P) caption: fixative unreported). Retrieval dependency is unreported; frozen sections or IF may be evaluated, but the supplied evidence does not establish that either is easier than paraffin IHC (HPA: actin-filament localization in ICC-IF). Interpret focal staining in the adipose comparator with care because vessels may contain smooth muscle even where adipocytes are negative (HPA: Not detected in adipocytes; UniProt P51911: smooth-muscle tissue specificity).
HPA tissue IHC evidence for CNN1
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 |
|---|---|---|---|---|
| Endometrium | Smooth muscle cells | High | Protein (IHC) | HPA → |
| Smooth muscle | Smooth muscle cells | High | Protein (IHC) | HPA → |
| Breast | Myoepithelial cells | Medium | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Adrenal gland | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Appendix | Endocrine cells | Not detected | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | Not detected | Protein (IHC) | HPA → |
| Bronchus | Respiratory epithelial cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced CNN1 IHC Tips
Troubleshoot CNN1 staining in paraffin IHC by checking retrieval, cell identity, cytoplasmic pattern and controls; use IF to resolve uncertain localisation.
How should I optimise retrieval when CNN1 staining is weak in paraffin sections?
Start with heat-mediated citrate retrieval at pH 6 for PA2224 paraffin IHC (datasheet PA2224). Compare 10, 20 and 30 minutes of heating on matched sections, keeping cooling, antibody incubation and detection constant (standard IHC optimisation). Judge recovery by cytoplasmic signal in smooth muscle cells and preservation of tissue structure, since smooth muscle is an expected positive compartment (HPA: high in smooth muscle cells). If signal remains weak, test an alkaline retrieval buffer as a fallback alongside citrate, rather than changing several conditions together (standard IHC optimisation). Excessive heat can damage morphology or raise diffuse background, so retain the mildest condition that gives interpretable staining (standard IHC practice).
Could fixation explain weak or uneven CNN1 staining?
CNN1-specific fixation sensitivity is unknown from the supplied evidence; the PA2224 placenta IHC caption does not state a fixative (PA2224 IHC(P) caption). Review each block’s recorded fixative and duration, then compare sections processed with documented, consistent conditions (standard IHC troubleshooting). If making new controls, use a consistent routine fixation schedule and vary retrieval separately so that a fixation effect can be distinguished from retrieval variation (standard IHC optimisation). Examine whether weak staining tracks with thick tissue, delayed fixation or poorly preserved morphology, while using smooth muscle cells as an expected positive reference (standard IHC practice; HPA: high in smooth muscle cells). Do not assign a CNN1-specific fixation effect without a direct comparison.
Where should convincing CNN1 signal appear in IHC sections?
Expect predominantly cytoplasmic staining in smooth muscle and myoepithelial cells, with high signal reported in smooth muscle cells and medium signal in breast myoepithelial cells (HPA: tissue IHC profile). CNN1 is associated with thin filaments and binds actin, and its approved subcellular location is actin filaments (UniProt P51911 function; HPA: subcellular). At 20× and 40×, assess whether the chromogen follows the cytoplasm of morphologically appropriate cells rather than nuclei or luminal material (standard IHC interpretation). Use adjacent unstained morphology or a cell-type marker on a serial section when boundaries are uncertain (standard IHC practice). Unexpected staining needs confirmation with controls before it is called CNN1 positive.
How can isoforms or phosphorylation affect interpretation of CNN1 staining?
CNN1 has 2 listed isoforms, but the supplied PA2224 caption gives no epitope sequence or isoform coverage (UniProt P51911 isoforms; PA2224 IHC(P) caption). It also has a calponin-homology domain at residues 28–131 and reported ROCK2 phosphorylation sites at 170, 175, 180, 184 and 259 (UniProt P51911 domains and modified residues). Without an antibody epitope map, neither isoform recognition nor sensitivity to those modifications can be inferred (standard antibody-validation principle). If two validated antibodies disagree, compare their documented epitopes and staining on adjacent sections under identical retrieval and detection conditions (standard IHC troubleshooting). Describe the observed staining as CNN1 immunoreactivity until the relevant specificity is established.
How can IF help resolve an ambiguous CNN1 IHC pattern?
Use IF as a separate localisation check: pair CNN1 with an expected smooth muscle marker such as ACTA2, which is listed in a CNN1-containing signalling complex (UniProt P51911 subunit). Choose spectrally separated fluorophores and place the weaker signal in a far-red channel when tissue autofluorescence interferes with shorter wavelengths (standard IF practice). CNN1 has no transmembrane segment, and actin filaments are its approved location, so permeabilisation should give antibody access to the cell interior (UniProt P51911 topology; HPA: subcellular). Compare a brief 0.1% detergent treatment with an unpermeabilised control while keeping fixation constant (standard IF optimisation). Include single-stain controls to assess bleed-through before interpreting overlap (standard IF practice).
What should I check when CNN1 chromogen appears throughout the section?
First compare signal in expected smooth muscle cells with adipocytes and respiratory epithelial cells, where CNN1 was not detected in the HPA tissue profile (HPA: high in smooth muscle cells; HPA: not detected in adipocytes and respiratory epithelial cells). Add a no-primary control to reveal secondary reagent or detection background, and confirm that the routine peroxidase block was performed before DAB detection (standard chromogenic IHC practice). Titrate the primary antibody and shorten chromogen development one variable at a time, recording exposure times across matched sections (standard IHC optimisation). Check whether pigment, folds or section edges retain colour independently of cell cytoplasm (standard histology troubleshooting). Specific CNN1 staining should remain cell associated and cytoplasmic (HPA: tissue IHC profile).
How should I score CNN1 across sections with different smooth muscle content? ⚠ ANSWER MARKED FOR VERIFICATION
Define the region of interest before scoring and distinguish smooth muscle or myoepithelial cells from other cells using morphology or an adjacent marker stain (HPA: tissue IHC profile; standard IHC practice). Report the percentage of positive eligible cells and, where intensity is reproducible, an H-score from 0–300 based on the proportions at intensity grades 0–3 (standard IHC scoring practice). For spatial studies, positive-cell density per mm² can supplement those measures (standard image-analysis practice). Normalise to the number or area of eligible smooth muscle or myoepithelial cells, since their abundance can differ between sections (HPA: tissue IHC profile; standard IHC quantification). Hold retrieval, detection and threshold settings constant across the comparison (standard IHC practice).
How do I distinguish true CNN1 staining from artefact?
A credible result places chromogen in the cytoplasm of morphologically appropriate smooth muscle or myoepithelial cells (HPA: highly selective cytoplasmic expression). Nuclear-only signal or staining restricted to unexpected cell populations conflicts with that reported pattern and warrants a control review (HPA: tissue IHC profile). Inspect section edges, folds and necrotic regions for staining that follows tissue damage rather than intact cells (standard histology troubleshooting). Compare no-primary and peroxidase-block controls when widespread colour could reflect detection background or endogenous enzyme activity (standard chromogenic IHC practice). Assess the pattern across more than 1 intact region and retain the localisation and control observations alongside any positive score (standard IHC interpretation).
Boster reagents
Best CNN1 / Calponin-1 IHC Antibodies
Anti-CNN1 antibodies have real paraffin-section IHC images from human placenta and appendicitis tissue, plus mouse and rat spleen (catalog IHC captions); IF/ICC is listed for M08065-1 (catalog applications).
Real IHC data
Anti-Calponin/CNN1 Antibody ®
Cat # PA2224
Real IHC data
Anti-Calponin CNN1 Rabbit Monoclonal Antibody
Cat # M08065-1
PA2224 has IHC images from human placenta and mouse and rat spleen; it lists human, mouse and rat reactivity (PA2224 image captions; catalog reactivity). M08065-1 has an IHC image from human appendicitis tissue and lists IF/ICC and human, mouse and rat reactivity (M08065-1 image caption; catalog applications and reactivity).
Which to pick: Choose PA2224 for paraffin-section tissue IHC when images across human, mouse and rat samples are useful (PA2224 image captions). Choose M08065-1 for IF/ICC because those applications are listed, and for paraffin-section IHC when its rabbit monoclonal clone and human appendicitis image fit the experiment (catalog applications and clone; M08065-1 image caption). Both list human, mouse and rat reactivity; the IHC captions do not report the fixative (catalog reactivity; catalog IHC captions).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P51911 (CNN1_HUMAN, Calponin-1).
- Human Protein Atlas. CNN1 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. CNN1 subcellular location (ICC-IF): Localized to the actin filaments..
- Human Protein Atlas. CNN1 antibody validation summary (2 antibodies).
- Histone lactylation modification promotes docetaxel resistance and tumor progression through CNN1-Mediated autophagy and cell cycle arrest in Castration-resistant prostate cancer. Cell death discovery 2026 — PMC13221474.
- Potential prognostic and immunotherapeutic value of calponin 1: A pan-cancer analysis. Frontiers in pharmacology 2023 — PMC10160448.
- Loss of calponin h1 confers anoikis resistance and tumor progression in the development of high-grade serous carcinoma originating from the fallopian tube epithelium. Oncotarget 2017 — PMC5617412.
- Smooth muscle calponin: an unconventional CArG-dependent gene that antagonizes neointimal formation. Arteriosclerosis, thrombosis, and vascular biology 2011 — PMC3179981.
- PubMed PMID:8526917 — UniProt-cited evidence.
- PubMed PMID:9332369 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CNN1 (Calponin-1). Expected localisation Cytoplasmic in smooth muscle and myoepithelial cells (HPA tissue IHC). Antigen retrieval: Citrate pH 6 HIER, heat-mediated (datasheet PA2224). Validated IHC antibody: PA2224 at 0.5-1μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Endometrium (Smooth muscle 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 PA2224); 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 retrieval: Citrate pH 6 , 20 min (datasheet PA2224); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet PA2224); 8. Primary antibody: Rabbit anti-CNN1, 0.5-1μg/ml (datasheet PA2224); 9. Primary incubation: Overnight at 4 °C (datasheet PA2224). Watch for: Fixation: Keep paraffin-section fixation consistent (standard IHC practice; not target-specific); effects on CNN1 staining are unclear.; Caveat: Myoepithelial cells can also stain in breast tissue (HPA tissue IHC); Isoform / epitope: 2 isoforms; epitope differences are unspecified (UniProt); Regulation: Enriched in smooth muscle (UniProt). Evidence: UniProt P51911, HPA tissue IHC · Enhanced, HPA ICC-IF · actin filaments., Datasheet PA2224, PMC13221474, PMC5617412. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CNN1/immunohistochemistry-ihc-guide.