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CTBP1 / C-terminal-binding protein 1 · IHC design guide
Design Immunohistochemistry for CTBP1
Plan chromogenic CTBP1 IHC in paraffin sections around the observed nuclear tissue pattern (HPA tissue IHC). Use HPA’s medium-staining and low-staining tissues for comparison, while accounting for its warning that the antibody may detect proteins from more than one gene (HPA tissue IHC).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CTBP1 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 | Nuclear staining in tissue; cytoplasm also annotated (HPA tissue IHC; UniProt) | |
| Staining pattern | General nuclear staining across tissue cell types (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6 HIER, heat-mediated (datasheet PB9425) | |
| Positive control | Adrenal gland+4 more · see all | |
| Negative control | None in HPA (detected in all 45 tissues); use no-primary + isotype controls |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation consistent across sections (standard IHC practice; not target-specific) | |
| Caveat | Staining may reflect proteins from more than one gene (HPA tissue IHC) | |
| Regulation | Expressed in germinal center B cells (UniProt) | |
| Isoform / epitope | Two isoforms; epitope coverage is unspecified (UniProt) |
Section 1
Recommended CTBP1 IHC & IF Protocols
The catalog antibody protocol uses citrate pH 6 heat retrieval (datasheet: PB9425). The published CTBP1 IHC protocols below provide additional details from melanoma, skin, and lung adenocarcinoma sections.
| Sample | Paraffin-embedded Mouse Thymus tissue; fixative not specified (datasheet PB9425) |
| Fixation | Image fixative and duration unreported (datasheet PB9425); 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 PB9425) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet PB9425) |
| Primary antibody | Rabbit anti-CTBP1, 0.5-1μg/ml (datasheet PB9425) |
| Primary incubation | Overnight at 4 °C (datasheet PB9425) |
| Detection | Streptavidin-biotin complex (SABC), DAB chromogen (datasheet PB9425) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | CTBP1-positive staining in glandular cells of adrenal gland (HPA tissue IHC: Medium). HPA tissue profile: General nuclear expression. No signal in the no-primary control. |
💡Decision noteStart with citrate pH 6 heat retrieval for paraffin sections (datasheet: PB9425); the lung adenocarcinoma protocol specifies 20 min at 96°C (PMC6549098).
Section 2
What Is the Expected CTBP1 Staining Pattern?
CTBP1 should show mainly nuclear staining in paraffin sections, with medium staining reported in several epithelial, glandular, hematopoietic and neural cell populations (HPA tissue IHC: general nuclear expression; listed positive cells). Cytoplasmic signal is biologically possible (UniProt Q13363: nucleus and cytoplasm). CTBP1 has no transmembrane segment (UniProt Q13363 topology). HPA rates its tissue IHC evidence Approved, with medium agreement between staining and RNA data and a warning that the antibodies may detect protein from more than one gene (HPA tissue IHC: reliability description).
| Nuclear chromogen is visible in bronchial respiratory epithelial cells, appendix glandular cells or bone marrow hematopoietic cells. | This matches the reported general nuclear pattern and medium staining in those cell populations (HPA tissue IHC: profile; positive entries). Score the named cell population and its nuclear signal; do not treat every stained cell in the section as equivalent. |
| Staining is predominantly at cell borders or outside cells, with little nuclear signal in a listed positive population. | That distribution conflicts with the observed nuclear IHC pattern (HPA tissue IHC: profile). CTBP1 has no transmembrane segment (UniProt Q13363 topology). Check slide morphology, the detection reagents and a control section before interpreting the border or extracellular color as CTBP1. |
| Strong color appears in a cell population expected to stain weakly, while the listed positive population is inconspicuous. | For example, thyroid glandular cells are listed as low, whereas adrenal glandular cells are listed as medium (HPA tissue IHC: low and positive entries). This mismatch raises concern for cross-reactivity or endogenous detection activity; it does not prove either cause. HPA warns that the tissue IHC antibodies may detect protein from more than one gene (HPA tissue IHC: reliability description). |
| Color is diffuse across tissue or appears similarly in cells, stroma and empty areas. | A diffuse deposit obscures the compartment and cell population needed to judge the reported nuclear pattern (HPA tissue IHC: profile). Review a no-primary control for background from detection chemistry, and reassess blocking, washing and chromogen development as general IHC practice. |
| No nuclear signal is seen in an interpretable section containing a listed positive cell population. | A negative result is unexpected when, for example, bronchial respiratory epithelial cells or appendix glandular cells are present; both have reported medium staining (HPA tissue IHC: positive entries). Check section quality and the staining run before calling CTBP1 absent. The HPA rating is Approved, with medium staining–RNA consistency (HPA tissue IHC: reliability description). |
💡Expected CTBP1 appearanceCall the result positive when nuclei in a listed cell population show discernible, roughly medium chromogenic staining; isolated membrane-like or diffuse extracellular color without that nuclear pattern is suspect (HPA tissue IHC: profile; medium positive entries; UniProt Q13363 topology).
| Which cells provide the comparison? | Use the named HPA populations: adrenal and appendix glandular cells, bronchial respiratory epithelial cells, bone marrow hematopoietic cells, caudate or cortical glia, cerebellar granular-layer cells, and cervical squamous epithelial cells are reported at medium level (HPA tissue IHC: positive entries). Thyroid, salivary and prostate glandular cells are listed as low, so they are weaker comparators (HPA tissue IHC: low entries). |
| How secure is antibody-specific interpretation? | The tissue pattern is rated Approved, with medium agreement between antibody staining and RNA expression; HPA also cautions that the antibodies may target protein from more than one gene (HPA tissue IHC: reliability description). The listed antibodies have IHC Approved status; that status alone does not resolve a surprising cell-specific stain (HPA antibodies: HPA018987, HPA044971, CAB004217). |
| Could compartment or processing explain the signal? | UniProt places CTBP1 in the nucleus and cytoplasm and lists no transmembrane segment or signal peptide (UniProt Q13363: subcellular location, topology, processing). A predominantly nuclear IHC pattern agrees with HPA observations; a discrete cytoplasmic component is plausible, but extracellular or membrane-only staining needs independent scrutiny (HPA tissue IHC: profile; UniProt Q13363: location, topology). |
| Do isoforms change the expected pattern? | Two isoforms are listed, but the supplied record gives no isoform-specific IHC distribution or antibody epitope (UniProt Q13363: isoforms 1 and 2). Do not infer that a tissue-specific or compartment-specific difference identifies an isoform. Likewise, the listed phosphoserines do not establish a staining change in paraffin sections (UniProt Q13363: modified residues). |
| What should an IF/ICC image show? | For the separate IF/ICC application, the HPA summary identifies enhanced nucleoplasmic localization (HPA subcellular ICC-IF: main location). This supports a nuclear localization check, without supplying an IF/ICC protocol or converting ICC-IF validation into IHC validation. HPA lists ICC Enhanced for HPA018987 and Supported for CAB004217 (HPA antibodies: ICC statuses). |
| Situation | Likely cause | Next action |
|---|---|---|
| Nuclear stain is absent from a listed positive cell population. | The run or section may be uninformative; the population is reported at medium staining, which is an observation rather than a guaranteed result in every section (HPA tissue IHC: positive entries). | Confirm that the named cells are present and intact, compare a separately stained positive section, then review the IHC-validated antibody dilution, antigen retrieval and detection steps against its instructions (general IHC practice). |
| Color is widespread even where no cells are present. | A diffuse deposit can reflect detection background or excessive development (general IHC practice); it does not match general nuclear expression (HPA tissue IHC: profile). | Inspect a no-primary control, shorten chromogen development if excessive, and review washes and blocking (general IHC practice). Judge the target result only after nuclei and tissue boundaries are readable. |
| Color outlines membranes or accumulates extracellularly. | The pattern conflicts with HPA general nuclear staining and is unsupported by CTBP1 topology (HPA tissue IHC: profile; UniProt Q13363: no transmembrane segment). | Compare the suspect area with intact nuclei on the same slide and with a no-primary control. If the border or extracellular pattern persists without nuclear enrichment, treat it as nonspecific until independently validated (general IHC interpretation). |
| A low-staining cell population looks stronger than the chosen positive comparator. | The comparison may reflect cross-reactivity or endogenous detection activity; HPA specifically warns that its tissue IHC antibodies may detect protein from more than one gene (HPA tissue IHC: reliability description). | Compare cell types on sections stained in the same run, inspect a no-primary control for detection activity, and seek an independent antibody or orthogonal evidence before assigning the unexpected signal to CTBP1 (general IHC practice). |
| Only cytoplasmic stain is visible. | Cytoplasmic CTBP1 is possible, but cytoplasm-only staining differs from the general nuclear tissue pattern and enhanced nucleoplasmic ICC-IF localization (UniProt Q13363: subcellular location; HPA tissue IHC: profile; HPA subcellular ICC-IF: main location). | Check whether nuclei are preserved and assess a listed positive cell population. Record cytoplasmic staining separately; avoid scoring it as the expected IHC result without corroboration (HPA tissue IHC: profile; general IHC interpretation). |
| The stain varies sharply between comparable sections. | Section handling or run conditions may differ (general IHC practice). The supplied HPA and UniProt evidence does not establish CTBP1-specific fixation sensitivity or an antigen retrieval requirement. | Compare section quality, retrieval, antibody dilution and chromogen development across runs using the same IHC procedure and a listed positive cell population (general IHC practice; HPA tissue IHC: positive entries). Do not attribute the variation specifically to CTBP1 epitope masking from these sources. |
Experiment evidence
IHC & IF images showing CTBP1 staining
PB9425 · IHCIHC analysis of CTBP1 using anti-CTBP1 antibody (PB9425). CTBP1 was detected in paraffin-embedded section of Mouse Thymus Tissue. Heat media
PB9425 · IHCIHC analysis of CTBP1 using anti-CTBP1 antibody (PB9425). CTBP1 was detected in paraffin-embedded section of Rat Spleen Tissue. Heat mediate
PB9425 · IFIF analysis of CTBP1 using anti-CTBP1 antibody (PB9425). CTBP1 was detected in immunocytochemical section of U20S cell. Enzyme antigen retri
PA1570 · IHCAnti-CtBP1 antibody, PA1570, IHC(P) IHC(P): Rat Brain Tissue
PA1570 · IHCIHC analysis of CTBP1 using anti-CTBP1 antibody (PA1570). CTBP1 was detected in a paraffin-embedded section of human colon tissue. Heat medi
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000159692-CTBP1/tissue/cerebral+cortex#imid_1397260
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000159692-CTBP1/tissue/colon#imid_1397170
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000159692-CTBP1/tissue/liver#imid_1397179
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000159692-CTBP1/tissue/kidney#imid_1397180
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA018987; green = CTBP1, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA018987; green = CTBP1, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CTBP1 IHC & IF
🧪Run appendix first and look for staining in its glandular cells (HPA: Medium in appendix glandular cells). HPA detects CTBP1 in all 45 scored tissues, so there is no supported negative tissue; no-primary and isotype controls carry the negative comparison, while any cells without specific brown nuclear signal on the positive slide serve only as a local background reference, not a validated CTBP1-negative population (HPA: no negative tissue rows; HPA: nucleoplasm localization).
Positive control tissue: Adrenal gland (Glandular cells, HPA Medium)
Negative control tissue: None in HPA: CTBP1 is detected in all 45 scored tissues. Use a no-primary (secondary-only) and an isotype control instead.
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show CTBP1 in A-431, U-251MG, U2OS, U2OS, siRNA 1 (10x), U2OS, siRNA 1 (40x), U2OS, siRNA 2 (10x), U2OS, siRNA 2 (40x), U2OS, scrambled (10x), U2OS, scrambled (40x), HeLa BAC 4639, HeLa , with annotated localisation: Nucleoplasm (enhanced) (HPA subcellular).
Technical controls: Include a secondary-only slide with no primary antibody, a concentration-matched rabbit IgG isotype control, and CTBP1 knockout tissue as a biological negative if available (selected PB9425 caption: rabbit primary; standard IHC controls). Block endogenous peroxidase before chromogenic detection and check background in the appendix section (selected PB9425 caption: DAB detection; standard IHC practice).
⚠️Feasibility: The selected PB9425 paraffin-section caption reports citrate retrieval at pH 6 for 20 minutes, but does not report its fixative; no target-specific fixation window or fixation effect is supplied (selected PB9425 caption). HPA shows nucleoplasmic CTBP1 in ICC-IF images, but the supplied evidence does not establish that IF or frozen sections are easier than paraffin IHC (HPA: subcellular ICC-IF). Assess endogenous peroxidase background when interpreting appendix DAB staining (standard IHC practice).
HPA tissue IHC evidence for CTBP1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Approved — Medium consistency between antibody staining and RNA expression data. Caution, targets protein from more than one gene.). 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 | Medium | Protein (IHC) | HPA → |
| Appendix | Glandular cells | Medium | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | Medium | Protein (IHC) | HPA → |
| Bronchus | Respiratory epithelial cells | Medium | Protein (IHC) | HPA → |
| Caudate | Glial cells | Medium | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| None in HPA: CTBP1 is detected in all 45 scored tissues. Use a no-primary (secondary-only) and an isotype control instead. | ||||
Section 3
Advanced CTBP1 IHC Tips
Troubleshoot CTBP1 staining in paraffin sections by checking retrieval, nuclear localisation, antibody specificity and section artefacts before comparing signal across samples.
What should I change when CTBP1 staining is weak after antigen retrieval?
Start with heat-mediated retrieval in citrate buffer at pH 6 (datasheet PB9425). The catalog antibody’s paraffin-section image used 20 minutes of retrieval before staining at 1 μg/ml overnight at 4°C (caption PB9425). If nuclear staining remains weak, compare carefully controlled heating times on adjacent sections while holding antibody concentration and detection constant (standard IHC practice). Check tissue preservation and a no-primary control before attributing weak signal to retrieval; excessive heating can damage section morphology and make nuclear scoring unreliable (standard IHC practice). Record the heating method and cooling conditions so the comparison can be reproduced (standard IHC practice).
Can the paraffin-section image tell me which fixation conditions preserve CTBP1?
Target-specific fixation sensitivity is unknown because the catalog antibody’s paraffin-section caption does not state a fixative (caption PB9425). Record each specimen’s fixative, fixation duration and processing history, then compare matched sections using the documented citrate pH 6, 20-minute retrieval condition (datasheet PB9425; standard IHC practice). Keep the 1 μg/ml primary concentration and overnight 4°C incubation constant while assessing nuclear signal and morphology (caption PB9425; standard IHC practice). Include a no-primary section to distinguish staining changes from detection background (standard IHC practice). Do not assign a CTBP1-specific fixation effect without a controlled comparison (caption PB9425: fixative unstated).
Should cytoplasmic CTBP1 staining count as a positive IHC result?
Assess nuclear staining first because the tissue IHC profile describes general nuclear expression and the subcellular profile identifies enhanced nucleoplasmic localisation (HPA tissue IHC; HPA subcellular). Cytoplasmic CTBP1 is also listed, so reproducible cytoplasmic signal is biologically plausible but requires independent specificity controls before scoring (UniProt Q13363 localisation; standard IHC practice). Score nuclear and cytoplasmic compartments separately on adjacent, comparably processed sections (standard IHC practice). If staining is exclusively diffuse cytoplasmic, inspect the no-primary control, section edges and cell morphology before interpreting it as CTBP1 (standard IHC practice). Use a nuclear counterstain to define cell boundaries consistently (standard IHC practice).
Can this IHC result distinguish CTBP1 isoforms or modified epitopes?
The record lists 2 CTBP1 isoforms, but the supplied antibody evidence does not map its epitope or establish isoform discrimination (UniProt Q13363 isoforms; caption PB9425). Phosphoserine sites at residues 300 and 422 are annotated, yet their effect on this antibody’s staining is untested here (UniProt Q13363 modified residues; caption PB9425). Treat chromogenic signal as antibody-reactive staining until an epitope map and appropriate specificity controls support a narrower claim (standard IHC practice). This matters because the tissue IHC assessment cautions that its antibody targets protein from more than one gene (HPA tissue IHC). Compare compartment and cell pattern alongside controls rather than inferring a specific isoform from stain intensity (standard IHC practice).
How should I compare a CTBP1 multiplex IF result with chromogenic IHC?
Use this page’s chromogenic paraffin-section result as the IHC reference; the IF/ICC workflow belongs to its separate guide (caption PB9425; application specification). In a multiplex experiment, pair CTBP1 with a marker of the expected cell population, such as germinal center B-cells, while evaluating nuclear overlap (UniProt Q13363 tissue specificity; HPA subcellular). Choose spectrally separated fluorophores and consider a longer-wavelength CTBP1 channel if tissue autofluorescence obscures shorter-wavelength signal (standard IF practice). Because CTBP1 has no transmembrane segment and is reported in the nucleus and cytoplasm, select permeabilisation that permits intracellular antibody access and confirm the observed compartment (UniProt Q13363 topology and localisation; standard IF practice). Do not assume fluorescence intensity and DAB intensity are directly interchangeable (standard IHC/IF practice).
How can I separate CTBP1 signal from DAB background?
The illustrated workflow used 10% goat serum blocking, a biotinylated secondary antibody, a streptavidin–biotin complex and DAB (caption PB9425). Include a no-primary section and inspect it for nonspecific secondary binding, endogenous biotin-associated staining and residual peroxidase activity; apply a peroxidase block as a general chromogenic IHC step (standard IHC practice). Check whether brown deposits cluster at folds, edges or damaged areas rather than within intact nuclei (standard IHC practice; HPA tissue IHC: general nuclear expression). If background persists, optimise blocking and detection conditions on matched sections before increasing primary antibody concentration (standard IHC practice). Keep DAB development comparable across samples (standard IHC practice).
What is a defensible way to quantify CTBP1 IHC across sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the tissue region and cell population before scoring, then measure the percentage of nuclei stained and, where intensity is reliable, an H-score on a 0–300 scale (standard IHC practice). Normalise positive-cell counts to the total evaluable nuclei in the same compartment, or report positive nuclei per mm² with the sampled area (standard IHC practice). Exclude folds, necrosis and poorly counterstained regions by a prespecified rule (standard IHC practice). Analyse cytoplasmic staining separately because the tissue profile describes general nuclear expression although CTBP1 can also be cytoplasmic (HPA tissue IHC; UniProt Q13363 localisation). Keep retrieval and DAB development consistent across compared sections (datasheet PB9425; standard IHC practice).
Which CTBP1 staining patterns warrant a specificity check?
Reproducible staining in intact nuclei fits the reported general nuclear tissue pattern and enhanced nucleoplasmic location (HPA tissue IHC; HPA subcellular). Cytoplasmic signal can be plausible, but exclusively diffuse staining or signal unrelated to intact cells merits a no-primary and antibody-specificity check (UniProt Q13363 localisation; standard IHC practice). Compare cell identity with the question being tested: expression in germinal center B-cells is documented, while the tissue IHC profile reports low tissue specificity (UniProt Q13363 tissue specificity; HPA tissue IHC). Discount edge staining, necrotic deposits and residual endogenous-enzyme DAB signal when judging positives (standard IHC practice). Interpret a positive stain cautiously because the HPA antibody assessment flags recognition of protein from more than one gene (HPA tissue IHC).
Boster reagents
Best CTBP1 / C-terminal-binding protein 1 IHC Antibodies
The catalog shows CTBP1 IHC in mouse thymus and rat brain paraffin sections (IHC image captions), plus PB9425 IF in human cells and human and rat tissue (PB9425 IF image captions).
Real IHC data
Anti-CtBP1 Antibody ®
Cat # PB9425
Real IHC data
Anti-C-terminal-binding protein 1 CtBP1 Antibody ®
Cat # PA1570
PB9425 will render with its mouse thymus paraffin-section IHC image; its catalog also lists IF and ICC applications (PB9425 image caption and catalog). PA1570 will render with its rat brain paraffin-section IHC image and is listed for IHC in human, mouse, and rat (PA1570 image caption and catalog).
Which to pick: For tissue IHC, choose PB9425 when its mouse thymus example is relevant, or PA1570 when its rat brain example is relevant; both list human, mouse, and rat reactivity (respective IHC image captions and catalog). For IF/ICC, choose PB9425, which lists both applications and has IF images; PA1570 lists IHC without IF or ICC (respective catalog entries). Both are rabbit antibodies with no clone specified, and their rendered IHC captions describe paraffin sections without reporting the fixative (respective catalog entries and IHC image captions).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry Q13363 (CTBP1_HUMAN, C-terminal-binding protein 1).
- Human Protein Atlas. CTBP1 tissue IHC expression (reliability: Approved).
- Human Protein Atlas. CTBP1 subcellular location (ICC-IF): Localized to the nucleoplasm..
- Human Protein Atlas. CTBP1 antibody validation summary (3 antibodies).
- CtBP1 Mediates Hypoxia-Induced Sarcomatoid Transformation in Hepatocellular Carcinoma. Journal of hepatocellular carcinoma 2022 — PMC8847960.
- CtBP1 is expressed in melanoma and represses the transcription of p16INK4a and Brca1. The Journal of investigative dermatology 2013 — PMC3711675.
- CtBP1 overexpression in keratinocytes perturbs skin homeostasis. The Journal of investigative dermatology 2014 — PMC4537778.
- CtBP1 interacts with SOX2 to promote the growth, migration and invasion of lung adenocarcinoma. Oncology reports 2019 — PMC6549098.
- PubMed PMID:7479821 — UniProt-cited evidence.
- PubMed PMID:9858600 — UniProt-cited evidence.
- PubMed PMID:15815621 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CTBP1 (C-terminal-binding protein 1). Expected localisation Nuclear staining in tissue; cytoplasm also annotated (HPA tissue IHC; UniProt). Antigen retrieval: Citrate pH 6 HIER, heat-mediated (datasheet PB9425). Validated IHC antibody: PB9425 at 0.5-1μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Adrenal gland (Glandular cells); negative None in HPA (detected in all 45 tissues); use no-primary + isotype controls. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded Mouse Thymus tissue; fixative not specified (datasheet PB9425); 2. Fixation: Image fixative and duration unreported (datasheet PB9425); 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 PB9425); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet PB9425); 8. Primary antibody: Rabbit anti-CTBP1, 0.5-1μg/ml (datasheet PB9425); 9. Primary incubation: Overnight at 4 °C (datasheet PB9425). Watch for: Fixation: Keep fixation consistent across sections (standard IHC practice; not target-specific); Caveat: Staining may reflect proteins from more than one gene (HPA tissue IHC); Isoform / epitope: Two isoforms ; epitope coverage is unspecified (UniProt); Regulation: Expressed in germinal center B cells (UniProt). Evidence: UniProt Q13363, HPA tissue IHC · Approved, HPA ICC-IF · nucleoplasm., Datasheet PB9425, PMC3711675, PMC4537778. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CTBP1/immunohistochemistry-ihc-guide.