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CNN1 / Calponin-1 · IHC design guide
Design Immunohistochemistry for CNN1
Plan CNN1 staining in paraffin sections using cytoplasmic smooth muscle staining as the principal readout (HPA tissue IHC). This guide covers controls, antigen retrieval, chromogenic detection and interpretation of myoepithelial staining (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 | Cytoplasm of 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 fixation consistent across sections. (standard IHC practice; not target-specific) | |
| Caveat | Smooth muscle in mixed tissue may dominate the signal (HPA tissue IHC) | |
| Regulation | Expression is enriched in smooth muscle (UniProt) | |
| Isoform / epitope | 2 isoforms; epitope coverage is unspecified (UniProt) |
Section 1
Recommended CNN1 IHC & IF Protocols
The catalog antibody protocol is followed by published CNN1 IHC methods from two PMC articles: tumor tissue staining and staining of clinical HGSC and normal fimbriae (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 pH 6 retrieval for the catalog antibody (datasheet: PA2224); adjust for a published protocol when using that study’s antibody and tissue (PMC5617412).
Section 2
What Is the Expected CNN1 Staining Pattern?
In paraffin section IHC, expect CNN1 in the cytoplasm of smooth muscle cells and breast myoepithelial cells (HPA tissue IHC: Enhanced; highly selective cytoplasmic expression). ICC-IF places it on actin filaments, while UniProt gives no subcellular annotation and reports no transmembrane segment (HPA ICC-IF: approved actin filament location; UniProt P51911: topology).
| Strong cytoplasmic staining outlines smooth muscle cells in a vessel wall or smooth muscle tissue. | This matches the reported smooth muscle pattern; confirm the stained cells by section morphology rather than judging color alone (HPA tissue IHC: high in smooth muscle cells; general IHC practice). |
| Moderate cytoplasmic staining follows myoepithelial cells in breast tissue. | This is an expected positive pattern at a lower reported level than smooth muscle; assess the cell layer and surrounding tissue separately (HPA tissue IHC: medium in breast myoepithelial cells; high in smooth muscle cells). |
| The dominant signal is nuclear or restricted to cell membranes. | Treat this as discordant with the reported cytoplasmic IHC pattern; check morphology, counterstain and detection controls before calling CNN1 positive (HPA tissue IHC: cytoplasmic; UniProt P51911: no transmembrane segment; general IHC practice). |
| Adipocytes or respiratory epithelial cells stain while expected smooth muscle cells do not. | Possible nonspecific antibody binding or endogenous detection activity needs investigation; the named cell types were reported as undetected, though nearby smooth muscle may still stain (HPA tissue IHC: adipocytes and respiratory epithelial cells not detected; general IHC practice). |
| A broad haze obscures cell borders, or a known-positive smooth muscle area is blank. | Neither appearance supports a reliable negative or positive call. Compare a reagent control and an intact positive area before interpreting the specimen (HPA tissue IHC: high in smooth muscle cells; general IHC practice). |
💡Expected CNN1 appearanceCall CNN1 positive when smooth muscle cytoplasm is strong, or breast myoepithelial cytoplasm is moderate; isolated nuclear or respiratory epithelial staining is discordant (HPA tissue IHC: high, medium, cytoplasmic; respiratory epithelial cells not detected).
| Cell type and tissue context | Score the stained cell, not the whole section: smooth muscle can be present beside a cell type reported as undetected (HPA tissue IHC: high in smooth muscle cells; adipocytes not detected). |
| Antibody validation | Two listed antibodies have Enhanced IHC status; this supports the tissue pattern but does not validate every staining condition (HPA antibodies: HPA014263 and CAB000007, IHC Enhanced; general IHC practice). |
| Antigen retrieval | No CNN1-specific retrieval setting is supplied. Compare standard retrieval conditions using a positive tissue control and consistent detection settings (general IHC practice). |
| Isoforms and phosphorylation | UniProt lists 2 isoforms and 5 modified residues; the record does not say whether either changes IHC staining or antibody recognition (UniProt P51911: isoforms and modified residues). |
| Processing and topology | The recorded chain spans residues 1–297, with no signal peptide, propeptide or transmembrane segment; these facts do not establish an epitope location (UniProt P51911: processing and topology). |
| Situation | Likely cause | Next action |
|---|---|---|
| No stain in a known-positive smooth muscle area. | A missing target-rich area, weak detection or a failed run is possible; the image alone cannot distinguish these (HPA tissue IHC: high in smooth muscle cells; general IHC practice). | Verify smooth muscle morphology, then review the run control, antibody dilution, retrieval and chromogen development under the same conditions (general IHC practice). |
| Diffuse brown signal covers many unrelated cells. | Background may arise from excess antibody, incomplete blocking or endogenous detection activity (general IHC practice). | Compare reagent controls; review blocking, antibody dilution, washes and detection chemistry before scoring any cytoplasmic signal (general IHC practice). |
| Nuclei or cell membranes carry the strongest signal. | That distribution conflicts with the reported cytoplasmic pattern; staining alone cannot identify its source (HPA tissue IHC: cytoplasmic; general IHC practice). | Check counterstain and detection controls, then compare the same run with positive smooth muscle morphology (general IHC practice; HPA tissue IHC: high in smooth muscle cells). |
| Adipocytes or respiratory epithelial cells appear positive. | Those cell types were reported as undetected; nearby smooth muscle or background can complicate visual assignment (HPA tissue IHC: both cell types not detected; general IHC practice). | Trace cell boundaries and adjacent smooth muscle, then use a reagent control to assess nonspecific or endogenous signal (general IHC practice). |
| Breast myoepithelial staining seems weaker than smooth muscle. | The reported levels differ: medium in breast myoepithelial cells and high in smooth muscle cells (HPA tissue IHC: respective levels). | Score each cell population against its expected pattern; do not require identical intensity across the two contexts (HPA tissue IHC: respective levels; general IHC practice). |
| What should an IF/ICC image show? | HPA reports an approved actin filament location in ICC-IF images; that finding does not define paraffin section resolution (HPA ICC-IF: actin filaments; general microscopy practice). | Use the separate IF/ICC guide for that application; interpret this paraffin IHC result by cytoplasmic signal in the expected cells (HPA tissue IHC: smooth muscle and myoepithelial cells). |
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), while epithelial cells on the same slide should serve as an internal negative comparison. Run adipose tissue as the negative specimen and score adipocytes, which are reported as not detected (HPA: Not detected in adipocytes); assess any vessels separately because they contain smooth muscle (standard histology; 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- and clonality-matched isotype control to assess detection background (standard IHC practice). Use CNN1 knockout material, if available, as a biological negative; quench endogenous peroxidase for chromogenic IHC and check tissue autofluorescence for IF (standard IHC/IF practice).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected PA2224 placenta IHC(P) caption does not state a fixative (selected SKU caption: fixative not stated). Retrieval dependence is unreported, so optimize antigen retrieval with the IHC-validated antibody rather than infer processing from HPA staining (HPA: tissue staining levels; selected SKU caption: IHC(P)). The supplied evidence does not establish whether frozen sections or IF are easier; for endometrium, score smooth muscle separately from other cell types, and account for endogenous peroxidase in chromogenic detection (HPA: High in endometrial smooth muscle cells; standard IHC practice).
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 sections by checking retrieval, cell identity, cytoplasmic localisation and detection controls (datasheet PA2224; HPA tissue IHC).
What retrieval should I try when CNN1 staining is weak in paraffin sections?
Use heat-mediated citrate antigen retrieval at pH 6 for PA2224 paraffin sections (datasheet PA2224). If staining remains weak, compare a longer heating interval with the original run while keeping section thickness, antibody conditions and detection constant (standard IHC practice). Let sections cool in retrieval buffer before washing, and include a smooth muscle control on each run because smooth muscle cells show high CNN1 staining (HPA tissue IHC). If signal remains absent, check primary antibody and detection performance before trying a different buffer or pH, since the supplied product-specific retrieval method is citrate pH 6 (datasheet PA2224; standard IHC practice).
How should I troubleshoot variable CNN1 staining across differently fixed sections?
Record the fixative, fixation duration and tissue processing conditions for each paraffin block before comparing CNN1 staining (standard IHC practice). Target-specific fixation sensitivity is unknown from the supplied evidence, and the PA2224 placenta IHC caption does not state a fixative (PA2224 tissue-IHC caption). For a controlled pilot, process matched tissue pieces with a consistent fixative and compare defined fixation intervals, such as 6 and 24 hours, using the same retrieval and detection run (standard IHC practice). Interpret any difference alongside preserved morphology and an internal smooth muscle control, rather than assigning it to a CNN1-specific fixation effect (HPA tissue IHC; standard IHC practice).
Which cellular pattern should count as CNN1-positive IHC staining?
Score cytoplasmic staining in smooth muscle and myoepithelial cells as the expected tissue IHC pattern (HPA tissue IHC). CNN1 is a thin filament-associated, actin-binding protein, and cellular imaging places it on actin filaments (UniProt P51911 function; HPA subcellular). A purely nuclear or sharply membranous DAB pattern should prompt a review of controls and morphology before it is counted, because the record gives no transmembrane segment and HPA describes cytoplasmic tissue staining (UniProt P51911 topology; HPA tissue IHC; standard IHC practice). Compare suspected positive cells with adjacent smooth muscle architecture at 2 magnifications so vessel walls and other compartments are identified consistently (standard IHC practice).
Could epitope choice explain discordant CNN1 staining between antibodies?
CNN1 has 2 listed isoforms, so first obtain each antibody’s immunogen or epitope map before comparing their IHC patterns (UniProt P51911 isoforms; standard IHC practice). The calponin-homology domain spans residues 28–131, while recorded phosphorylation sites include residues 170, 175, 180, 184 and 259 (UniProt P51911 domains and modified residues). Without epitope mapping, those positions do not establish whether either antibody distinguishes isoforms or is sensitive to phosphorylation (UniProt P51911 record; standard IHC practice). Compare staining in matched sections with high-staining smooth muscle cells and an appropriate negative compartment, then investigate discordance before combining scores (HPA tissue IHC; standard IHC practice).
How can I check CNN1 localisation by IF alongside tissue IHC?
For a separate IF experiment, multiplex CNN1 with a smooth muscle marker such as ACTA2 and assess whether intracellular signals occupy the expected cells (UniProt P51911 subunit; HPA tissue IHC; standard IF practice). Select spectrally separated fluorophores, favouring a far-red channel when tissue autofluorescence obscures shorter wavelengths, and acquire single-stain controls (standard IF practice). Because CNN1 has no transmembrane segment and is associated with actin filaments, use mild permeabilisation to give antibody access to intracellular epitopes; the supplied evidence does not map the antibody epitope (UniProt P51911 topology and function; standard IF practice). Optimise IF fixation independently, and compare its filament-associated pattern with cytoplasmic IHC staining without treating either image as a fixation protocol for the other (HPA subcellular; HPA tissue IHC; PA2224 tissue-IHC caption).
How do I distinguish CNN1 staining from diffuse brown background?
Run a no-primary control and review peroxidase blocking when diffuse DAB signal appears, since endogenous enzyme activity can contribute to chromogenic background (standard IHC practice). Check whether brown signal follows smooth muscle or myoepithelial cytoplasm rather than every cell, using the reported selective CNN1 tissue pattern as a reference (HPA tissue IHC). If background persists, titrate the catalog antibody and shorten chromogen development in separate pilot sections while holding retrieval constant at citrate pH 6 (datasheet PA2224; standard IHC practice). Compare the pilot with a high-staining smooth muscle control and a compartment reported as negative, such as adipocytes, before accepting weaker staining as specific (HPA tissue IHC; standard IHC practice).
How should I quantify CNN1 staining when smooth muscle content varies? ⚠ ANSWER MARKED FOR VERIFICATION
Identify smooth muscle or myoepithelial regions before scoring, because CNN1 tissue staining is selective for those cells (HPA tissue IHC). For each region, report the percentage of positive target cells and an H-score calculated from intensity grades 0–3 multiplied by their corresponding percentages, yielding a 0–300 scale (standard IHC practice). Normalise comparisons to the number of eligible target cells or their annotated area rather than total section area when smooth muscle content differs (standard IHC practice). Keep the staining threshold, region selection and image acquisition settings consistent across specimens, and record excluded necrotic or damaged areas (standard IHC practice).
What findings would make an apparent CNN1-positive result unconvincing?
A convincing result places cytoplasmic signal in smooth muscle or myoepithelial cells, with suitable morphology and a working positive control (HPA tissue IHC; standard IHC practice). Re-examine apparent nuclear or exclusively membranous staining, because HPA describes cytoplasmic expression and the CNN1 record lists no transmembrane segment (HPA tissue IHC; UniProt P51911 topology). Treat signal confined to section edges, necrotic regions or the no-primary control as suspect, and check peroxidase blocking before interpreting DAB deposits (standard IHC practice). If staining instead predominates in a reported negative compartment, such as adipocytes or respiratory epithelial cells, repeat the run with positive and negative controls before scoring it (HPA tissue IHC; standard IHC practice).
Boster reagents
Best CNN1 / Calponin-1 IHC Antibodies
Anti-CNN1 antibodies with real IHC images cover paraffin sections of human placenta and appendicitis tissue, and mouse and rat spleen (catalog IHC captions).
Real IHC data
Anti-Calponin/CNN1 Antibody ®
Cat # PA2224
Real IHC data
Anti-Calponin CNN1 Rabbit Monoclonal Antibody
Cat # M08065-1
PA2224 is listed for IHC and shows human placenta and mouse and rat spleen in paraffin sections (PA2224 applications and IHC captions). M08065-1 is listed for IHC, IF and ICC, with a paraffin-section IHC image from human appendicitis tissue (M08065-1 applications and IHC caption).
Which to pick: For tissue IHC across human, mouse and rat, choose PA2224: all three species are listed as reactive and represented in its IHC captions (PA2224 reactivity and IHC captions). For IF/ICC, choose the rabbit monoclonal M08065-1 because those applications are listed, with a stated IF dilution of 1:50; its supplied image documents IHC, not IF (M08065-1 catalog applications, clone, IF dilution and IHC caption). Both IHC captions describe paraffin sections but do not report the fixative (PA2224 and M08065-1 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 Cytoplasm of 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 fixation consistent across sections. (standard IHC practice; not target-specific); Caveat: Smooth muscle in mixed tissue may dominate the signal (HPA tissue IHC); Isoform / epitope: 2 isoforms; epitope coverage is unspecified (UniProt); Regulation: Expression is 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.