This website uses cookies to ensure you get the best experience on our website.
- Table of Contents
S100A1 / Protein S100-A1 · IHC design guide
Design Immunohistochemistry for S100A1
Plan S100A1 paraffin IHC using heart and skeletal muscle as strong-staining tissues (HPA tissue IHC). This guide covers fixation consistency, antibody titration, controls, and interpretation of cytoplasmic and nuclear staining (HPA tissue IHC).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
S100A1 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 and nuclear tissue staining (HPA tissue IHC) | |
| Staining pattern | Strong in cardiomyocytes and skeletal myocytes (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen) | |
| Positive control | Appendix+4 more · see all | |
| Negative control | Adrenal gland+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation conditions consistent across sections. (standard IHC practice; not target-specific) | |
| Caveat | Staining and RNA show medium consistency (HPA tissue IHC) | |
| Regulation | Expression regulation is not established (UniProt) | |
| Isoform / epitope | No reported isoforms; one unprocessed 1–94 chain (UniProt) |
Section 1
Recommended S100A1 IHC & IF Protocols
The catalog antibody protocol is provided separately. These published S100A1 IHC protocols cover heart, ovarian, thyroid, and liver tumor tissues (PMC3663776; PMC3040237; PMC8408122; PMC6017223).
| Sample | Paraffin-embedded human kidney tissue; fixative not specified (datasheet M02503-1) |
| Fixation | Image fixative and duration unreported (datasheet M02503-1); 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 monoclonal (clone ABCF-19) anti-S100A1, 1:100-1:500 (datasheet M02503-1) |
| 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 | S100A1-positive staining in endocrine cells of appendix (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic and nuclear expression in several tissue types. Most abundant in CNS, salivary glands, melaocytes, skeletal and heart muscle. No signal in the no-primary control. |
💡Decision noteStart with citrate pH 6.0 HIER at 95–98 °C for 20 min (page retrieval); the published microwave protocols specify different or incomplete conditions (PMC3663776; PMC6017223).
Section 2
What Is the Expected S100A1 Staining Pattern?
S100A1 staining should be prominent in cardiomyocytes and skeletal myocytes (HPA: High in both), with cytoplasmic staining expected (UniProt P23297: cytoplasm; HPA: cytoplasmic and nuclear tissue expression). UniProt also places S100A1 at the sarcoplasmic reticulum and mitochondrion and reports no transmembrane segment (UniProt P23297). HPA rates its tissue IHC evidence Enhanced, while describing only medium consistency between antibody staining and RNA expression (HPA: reliability).
| Strong staining in heart cardiomyocytes or skeletal myocytes, chiefly within the cell body. | This fits the expected positive-cell distribution (HPA: High in both cell types) and cytoplasmic localisation (UniProt P23297; HPA: tissue IHC). Compare intensity within the same staining run. |
| Staining appears exclusively along cell borders, with little intracellular signal. | A border-only pattern conflicts with the reported intracellular locations and lack of a transmembrane segment (UniProt P23297). Review morphology and detection background before assigning S100A1 positivity. |
| Strong staining appears in bone-marrow hematopoietic cells or bronchial respiratory epithelium. | HPA reports S100A1 as not detected in those specific cell populations (HPA: tissue IHC). Consider antibody cross-reactivity or endogenous detection activity; check controls before interpreting the signal. |
| Color spreads across stroma or empty areas and obscures cell boundaries. | That distribution does not establish cellular S100A1 localisation (UniProt P23297: intracellular locations). General IHC practice: assess background using an appropriate negative detection control and review washing and blocking. |
| Cardiomyocytes remain unstained in a heart section with readable tissue morphology. | Heart cardiomyocytes are a strong expected positive population (HPA: High; UniProt P23297: highly prevalent in heart). Investigate the staining run before treating other negative results as informative. |
💡Expected S100A1 appearanceCall a slide positive when cardiomyocytes or skeletal myocytes show clear, predominantly cytoplasmic staining (HPA: High; UniProt P23297: cytoplasm); widespread cell-free color or strong staining in HPA-negative cell types is suspect (HPA: tissue IHC).
| Choice of reference tissue | Heart cardiomyocytes and skeletal myocytes provide high-staining comparisons (HPA: High); breast adipocytes are listed at Medium (HPA: tissue IHC). Judge the identified cell population, not an entire section. |
| Compartment used for scoring | Cytoplasmic staining is supported in tissue IHC, but HPA also describes nuclear expression in several tissues (HPA: tissue profile). Nuclear signal alone needs tissue and antibody context. |
| Protein topology and processing | S100A1 has no transmembrane segment or signal peptide and is listed as a single 1–94 chain (UniProt P23297). These facts favor intracellular interpretation; they do not establish retrieval conditions. |
| IHC antibody evidence | HPA006462 and CAB002599 each have Enhanced IHC validation (HPA: antibody records). HPA still reports medium staining–RNA consistency (HPA: reliability); use the observed cell pattern alongside run controls. |
| IF/ICC Q&A: where should fluorescence appear? | Mainly in cytosol; nucleoplasm and Golgi are additional reported locations (HPA: ICC-IF subcellular). This cell-image evidence does not prescribe an IHC-P protocol or establish identical prominence in tissue sections. |
| Situation | Likely cause | Next action |
|---|---|---|
| No staining in heart cardiomyocytes. | A failed staining or detection step is possible; heart cardiomyocytes are High by HPA (HPA: tissue IHC). | General IHC practice: verify the positive control, antibody application, detection reagents, retrieval settings and counterstain; repeat the run if its control failed. |
| Only nuclear staining is visible. | Nuclear expression can occur in tissue (HPA: tissue profile), but cytoplasm is also reported (HPA: tissue profile; UniProt P23297). | Check the exact tissue and cell type against HPA, then compare a validated positive section and a negative detection control before scoring. |
| A nominally negative cell population stains strongly. | Cross-reactivity or endogenous detection activity is possible; HPA lists specific unstained populations, including bone-marrow hematopoietic cells (HPA: tissue IHC). | Confirm cell identity and assess a negative detection control; general IHC practice: address endogenous activity according to the detection chemistry. |
| Diffuse color makes individual cells hard to score. | General IHC practice: nonspecific detection background or inadequate washing can obscure localisation; diffuse cell-free color is not a reported S100A1 compartment (UniProt P23297). | Review the negative detection control, washing, blocking and chromogen development; score only clearly resolved cellular signal. |
| A border-only pattern dominates the section. | This conflicts with the reported intracellular locations and absent transmembrane segment (UniProt P23297), though staining appearance alone cannot identify the artifact. | Recheck morphology and the positive control; compare an independently validated antibody where available (HPA: two Enhanced IHC antibody records). |
| Staining differs between sections or runs. | Technical variation is possible; HPA's Enhanced IHC rating coexists with medium staining–RNA consistency (HPA: reliability and antibody records). | General IHC practice: compare controls, tissue preservation, retrieval and detection settings across runs before interpreting a biological difference. |
Experiment evidence
IHC & IF images showing S100A1 staining
M02503-1 · IHCImmunohistochemical analysis of paraffin-embedded human kidney, using S100 Antibody.
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000160678-S100A1/tissue/cerebral+cortex#imid_2273956
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000160678-S100A1/tissue/colon#imid_2273866
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000160678-S100A1/tissue/liver#imid_2273883
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000160678-S100A1/tissue/kidney#imid_2273884
HPA · ICC-IF Hep-G2Human Protein Atlas immunofluorescence, Hep-G2, antibody HPA006462; green = S100A1, blue = nucleus, red = microtubules.
HPA · ICC-IF Hep-G2Human Protein Atlas immunofluorescence, Hep-G2, antibody HPA006462; green = S100A1, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for S100A1 IHC & IF
🧪Run heart muscle first: cardiomyocytes should stain (HPA: High in cardiomyocytes). Run bone marrow as the negative tissue, focusing on hematopoietic cells (HPA: Not detected in hematopoietic cells); on the heart slide, use adjacent noncardiomyocyte cells as internal background comparators, checking that any stain is at background level against the no-primary control rather than assuming those cells lack S100A1 (HPA: High in cardiomyocytes).
Positive control tissue: Appendix (Endocrine cells, HPA High)
Negative control tissue: Adrenal gland (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show S100A1 in Hep-G2, SK-MEL-30, with annotated localisation: Cytosol (supported) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control, a host-species- and clonality-matched isotype control, and a biological specificity control using knockout tissue or a validated immunizing-peptide block (standard IHC practice). In heart sections, quench endogenous peroxidase and inspect intrinsic pigment before interpreting chromogen; for IF, check tissue autofluorescence with an unstained section (standard IHC/IF practice).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported in the supplied evidence, and the selected M02503-1 paraffin-section kidney caption does not state the fixative (selected-SKU tissue-IHC caption: fixative not stated). Retrieval dependence is also unreported; optimize antigen retrieval empirically for paraffin IHC, without treating the caption or HPA staining as evidence of fixation or specimen processing (selected-SKU tissue-IHC caption; HPA: High in heart cardiomyocytes). The evidence does not establish that frozen sections or IF are easier; for IF/ICC, HPA reports mainly cytosolic localization, with additional nucleoplasmic and Golgi signal, and heart pigment or autofluorescence should be checked against background controls (HPA subcellular: cytosol supported; nucleoplasm and Golgi approved; standard IHC/IF practice). The selected M02503-1 tissue-IHC caption documents paraffin sections, but does not specify the fixative (selected-SKU IHC image M02503-1).
HPA tissue IHC evidence for S100A1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — Medium 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 |
|---|---|---|---|---|
| Appendix | Endocrine cells | High | Protein (IHC) | HPA → |
| Cerebellum | Granular cells - cytoplasm/membrane | High | Protein (IHC) | HPA → |
| Duodenum | Endocrine cells | High | Protein (IHC) | HPA → |
| Heart muscle | Cardiomyocytes | High | Protein (IHC) | HPA → |
| Rectum | Endocrine cells | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adrenal gland | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | Not detected | Protein (IHC) | HPA → |
| Bronchus | Respiratory epithelial cells | Not detected | Protein (IHC) | HPA → |
| Cervix | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Esophagus | Squamous epithelial cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced S100A1 IHC Tips
Troubleshoot S100A1 staining in paraffin sections by checking retrieval, cell identity, compartment, controls and scoring before interpreting chromogenic signal.
How should I retrieve S100A1 when staining is weak in paraffin sections?
Start with citrate buffer at pH 6.0 for heat-induced retrieval at 95–98 °C for 20 minutes (page retrieval rule). Keep section thickness, heating conditions and detection settings consistent while comparing a weak specimen with a heart-muscle control, where cardiomyocyte staining is high (HPA tissue IHC). If both sections remain weak, check whether the retrieval vessel reached the intended temperature and whether sections stayed covered by buffer throughout heating (standard IHC practice). Compare a carefully adjusted retrieval duration on adjacent sections, because excessive heating can damage tissue morphology and make cell-level interpretation unreliable (standard IHC practice).
Could fixation explain weak or uneven S100A1 staining?
Target-specific fixation sensitivity is unknown from the supplied evidence; the catalog antibody’s kidney image identifies paraffin embedding but does not state a fixative (M02503-1 caption). Record the fixative, fixation duration and processing history for each specimen before comparing staining intensity across blocks (standard IHC practice). On adjacent sections, compare preserved morphology and staining in a heart-muscle control, whose cardiomyocytes have high reported S100A1 expression (HPA tissue IHC). If a block stains unevenly, check whether the pattern follows tissue preservation or section edges, and repeat staining with matched processing conditions before attributing differences to S100A1 biology (standard IHC practice).
Should S100A1 staining be cytoplasmic, nuclear or organelle-associated?
Expect predominantly intracellular staining: S100A1 is annotated in cytoplasm, sarcoplasmic reticulum and mitochondria, with no transmembrane segment (UniProt P23297). The HPA subcellular profile supports cytosol as the main location and also records nucleoplasm and Golgi apparatus, so nuclear signal alone is not automatically artefactual (HPA subcellular). In paraffin sections, compare each compartment with cell morphology and a matched positive control before assigning a biological location (standard IHC practice). Treat diffuse staining across unrelated cells or staining restricted to damaged edges cautiously, and review the no-primary control and tissue preservation alongside the chromogen pattern (standard IHC practice).
How can epitope accessibility or related S100 proteins complicate staining?
The supplied record lists zero isoforms, a single 1–94 protein chain and two EF-hand domains at residues 13–48 and 50–85 (UniProt P23297). It also records S-nitrosocysteine at residue 86 and S100A1-containing dimers, but does not identify the catalog antibody’s epitope (UniProt P23297; M02503-1 caption). Therefore, do not infer that a specific modification or dimer state causes weak paraffin-section staining without direct antibody evidence (UniProt P23297; standard IHC practice). Assess specificity with appropriate positive and negative tissues, no-primary controls and any available antibody-validation data before interpreting an unexpected compartment as S100A1 (HPA tissue IHC; standard IHC practice).
How should I assess S100A1 in a multiplex IF follow-up?
Use the separate IF/ICC workflow for a multiplex follow-up, pairing S100A1 with a marker that identifies the expected cell type, such as cardiomyocytes in heart muscle (HPA tissue IHC; standard IF practice). Select spectrally separated fluorophores and inspect unstained tissue so its autofluorescence does not masquerade as the S100A1 channel (standard IF practice). S100A1 has no transmembrane segment and is mainly cytosolic, so permeabilisation should permit antibody access to intracellular epitopes (UniProt P23297; HPA subcellular). Optimise permeabilisation against morphology and background, and use single-channel and no-primary controls when assessing colocalisation (standard IF practice). No target-specific IF fixation condition is supplied here (supplied evidence).
What should I check when brown signal appears outside expected S100A1-positive cells?
First inspect a no-primary section and the peroxidase-block step; endogenous enzyme activity and nonspecific detection can produce chromogen independent of S100A1 binding (standard IHC practice). Compare the suspect area with a heart-muscle positive control and an HPA-listed negative cell population, such as bone-marrow hematopoietic cells (HPA tissue IHC). If staining concentrates at cut edges, folds or damaged tissue, review section quality, washing and detection exposure before increasing primary-antibody concentration (standard IHC practice). Score only intact cells with interpretable morphology, and document persistent background separately from signal assigned to S100A1 (standard IHC practice).
How should I quantify S100A1 across paraffin sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and compartment before scoring; cardiomyocytes show high S100A1 staining in the HPA tissue profile (HPA tissue IHC). For cell-based comparisons, report the percentage of positive target cells and an H-score combining that percentage with intensity categories, using the same thresholds across sections (standard IHC practice). If measuring stained area or positive-cell density, normalise to the area of intact, evaluable tissue in mm², and record the target-cell fraction so changing tissue composition does not mimic regulation (standard IHC practice). Exclude folds, necrosis and edge artefacts consistently, and compare batches only after checking control staining and acquisition settings (standard IHC practice).
How do I distinguish genuine S100A1 staining from an artefact?
A plausible positive pattern should occur in identifiable cells and fit the expected intracellular distribution, chiefly cytoplasmic with documented additional nuclear localisation (UniProt P23297; HPA subcellular). Heart-muscle cardiomyocytes and skeletal-muscle myocytes are high-staining reference populations, whereas bone-marrow hematopoietic cells are listed as not detected (HPA tissue IHC). Treat isolated signal in an unexpected cell population, at a section edge or within necrotic tissue as provisional until morphology and controls support it (standard IHC practice). If brown signal persists without primary antibody, review endogenous peroxidase blocking and detection background before assigning it to S100A1 (standard IHC practice).
Boster reagents
Best S100A1 / Protein S100-A1 IHC Antibodies
M02503-1 has an IHC image from paraffin-embedded human kidney; Human and Mouse reactivity are listed, with no IF data supplied (IHC image caption; catalog reactivity and images).
Real IHC data
Anti-S100 S100A1 Rabbit Monoclonal Antibody
Cat # M02503-1
M02503-1 will render with an IHC image of paraffin-embedded human kidney (IHC image caption). Its listed applications include IHC, and its listed reactivity is Human and Mouse; no IF image is supplied (catalog applications, reactivity, and images).
Which to pick: For tissue IHC, choose M02503-1, a rabbit monoclonal with a listed IHC dilution of 1:100–1:500 and an image from paraffin-embedded human kidney; the fixative is unreported (catalog host, clone, and dilution; IHC image caption). For IF/ICC, no listed SKU has IF validation or an IF image (catalog applications and images). For cross-species work, M02503-1 lists Human and Mouse reactivity, though its supplied IHC image shows human kidney only (catalog reactivity; IHC image caption).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P23297 (S10A1_HUMAN, Protein S100-A1).
- Human Protein Atlas. S100A1 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. S100A1 subcellular location (ICC-IF): Mainly localized to the cytosol. In addition localized to the nucleoplasm and the Golgi apparatus..
- Human Protein Atlas. S100A1 antibody validation summary (2 antibodies).
- Immunohistochemical detection of S100A1 in the postmortem diagnosis of acute myocardial infarction. Diagnostic pathology 2013 — PMC3663776.
- S100A1 expression in ovarian and endometrial endometrioid carcinomas is a prognostic indicator of relapse-free survival. American journal of clinical pathology 2009 — PMC3040237.
- S100A1 is a Potential Biomarker for Papillary Thyroid Carcinoma Diagnosis and Prognosis. Journal of Cancer 2021 — PMC8408122.
- Interaction of S100A1 with LATS1 promotes cell growth through regulation of the Hippo pathway in hepatocellular carcinoma. International journal of oncology 2018 — PMC6017223.
- PubMed PMID:1384693 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
- PubMed PMID:19054851 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for S100A1 (Protein S100-A1). Expected localisation Cytoplasmic and nuclear tissue staining (HPA tissue IHC). Antigen retrieval: Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen). Validated IHC antibody: M02503-1 at 1:100-1:500 (the product's own IHC validation image is shown). Controls (HPA): positive Appendix (Endocrine cells); negative Adrenal gland. IHC workflow; specimen preparation unspecified. Protocol steps: 1. Sample: Paraffin-embedded human kidney tissue; fixative not specified (datasheet M02503-1); 2. Fixation: Image fixative and duration unreported (datasheet M02503-1); 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 monoclonal (clone ABCF-19) anti-S100A1, 1:100-1:500 (datasheet M02503-1); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: Keep fixation conditions consistent across sections. (standard IHC practice; not target-specific); Caveat: Staining and RNA show medium consistency (HPA tissue IHC); Isoform / epitope: No reported isoforms; one unprocessed 1–94 chain (UniProt); Regulation: Expression regulation is not established (UniProt). Evidence: UniProt P23297, HPA tissue IHC · Enhanced, HPA ICC-IF · Mainly localized to the cytosol. In addition localized to the…, Datasheet M02503-1, PMC3663776, PMC3040237. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/S100A1/immunohistochemistry-ihc-guide.