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CHTOP / Chromatin target of PRMT1 protein · IHC design guide
Design Immunohistochemistry for CHTOP
Plan CHTOP paraffin IHC around the nuclear staining observed in most tissues (HPA tissue IHC). This guide covers consistent fixation, the catalog antibody’s 2–5 μg/mL IHC range (datasheet A07770-2), and interpretation of staining with medium consistency against RNA expression (HPA tissue IHC).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CHTOP 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 most tissues (HPA tissue IHC) | |
| Staining pattern | Nuclear staining across most tissues (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet A07770-2) | |
| Positive control | Adipose tissue+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 tissue sections. (standard IHC practice; not target-specific) | |
| Caveat | Staining and RNA show medium consistency (HPA tissue IHC) | |
| Regulation | Low tissue RNA specificity (HPA tissue RNA) | |
| Isoform / epitope | 3 isoforms; epitope differences are unknown (UniProt) |
Section 1
Recommended CHTOP IHC & IF Protocols
The catalog antibody’s IHC-P protocol (datasheet: A07770-2) is accompanied by two published paraffin-section IHC protocols (PMC6465198; PMC6660285).
| Sample | Paraffin-embedded human breast cancer tissue; fixative not specified (datasheet A07770-2) |
| Fixation | Image fixative and duration unreported (datasheet A07770-2); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat retrieval: EDTA pH 8.0 (datasheet A07770-2); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A07770-2) |
| Primary antibody | Rabbit anti-CHTOP, 2 μg/ml (datasheet A07770-2) |
| Primary incubation | Overnight at 4 °C (datasheet A07770-2) |
| Detection | HRP-conjugated secondary, DAB chromogen (datasheet A07770-2) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | CHTOP-positive staining in adipocytes of adipose tissue (HPA tissue IHC: High). HPA tissue profile: Nuclear expression in most tissues. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated EDTA retrieval at pH 8.0 (datasheet: A07770-2); the published methods provide citrate and target-retrieval-solution alternatives (PMC6465198; PMC6660285).
Section 2
What Is the Expected CHTOP Staining Pattern?
CHTOP should appear predominantly in nuclei across many tissues (HPA: nuclear expression in most tissues; UniProt Q9Y3Y2: nuclear localisation). HPA reports High staining in adipocytes, adrenal glandular cells, bronchial respiratory epithelial cells, bone marrow hematopoietic cells and several other listed cell populations (HPA: tissue IHC). These are reference patterns, with Approved IHC reliability and medium consistency between staining and RNA data (HPA: tissue IHC). CHTOP has no transmembrane segment (UniProt Q9Y3Y2: topology).
| Clear nuclear staining in bronchial respiratory epithelial cells, with little signal outside nuclei. | This fits a listed High-staining population and the reported nuclear tissue profile (HPA: bronchus, High; HPA: nuclear expression in most tissues). Assess signal against a matched negative control and tissue morphology before calling the section positive (general IHC practice). |
| Strong, widespread membrane or cytoplasmic colour with weak or absent nuclear signal. | The dominant compartment conflicts with CHTOP's nuclear localisation (UniProt Q9Y3Y2: subcellular location; HPA: tissue IHC profile). Consider nonspecific detection or a staining artefact; verify the compartment against a nuclear counterstain and a control section (general IHC practice). |
| Signal is strongest outside the expected cell population in a listed reference tissue. | For example, HPA identifies glial cells as High in caudate and cells in the granular layer as High in cerebellum (HPA: tissue IHC). Unexpected staining may reflect cross-reactivity or endogenous detection activity; identify cells by morphology and compare with appropriate controls (general IHC practice). |
| Colour is diffuse across stroma, empty spaces or most of the section, obscuring nuclei. | Such background does not resolve the reported nuclear pattern (HPA: tissue IHC profile). Check a reagent-only control, blocking, washing and detection conditions to locate nonspecific signal (general IHC practice). Background alone cannot establish CHTOP expression. |
| No nuclear signal appears in bronchial respiratory epithelial cells or adrenal glandular cells. | Both are listed as High-staining populations (HPA: bronchus and adrenal gland). First check tissue preservation, retrieval, antibody and detection performance with controls (general IHC practice). HPA's Approved rating has medium RNA–staining consistency, so one negative section does not establish biological absence (HPA: tissue IHC). |
💡Expected CHTOP appearanceCall a convincing positive when nuclei are discernibly stained in a listed High-staining population, such as bronchial respiratory epithelial cells (HPA: bronchus, High; HPA: nuclear tissue profile); dominant membrane colour or diffuse section-wide colour is suspect (UniProt Q9Y3Y2: nuclear localisation; general IHC practice).
| Nuclear detail | UniProt places CHTOP in nucleoplasm, nucleolus and nuclear speckles, including perispeckle regions (UniProt Q9Y3Y2: subcellular location). HPA tissue IHC supports nuclear expression broadly; routine chromogenic sections need not resolve individual speckles (HPA: tissue IHC; general IHC practice). |
| Reference tissue choice | Use a listed High-staining cell population as a positive reference, such as bone marrow hematopoietic cells or breast adipocytes (HPA: tissue IHC). HPA reports low tissue specificity and supplies no negative tissue here; an unlisted tissue is not a validated negative (HPA: RNA specificity and supplied tissue IHC). |
| Antibody and epitope | HPA028647 is Approved for IHC, while the supplied record gives no IHC status for HPA030540 (HPA: antibody validation). UniProt lists three isoforms and several modified residues, but no antibody epitope is supplied; isoform recognition or modification-dependent staining cannot be predicted (UniProt Q9Y3Y2: isoforms and modified residues). |
| IF/ICC Q&A: What localisation should fluorescence show? | Nuclear speckles are the supported main ICC-IF location (HPA: subcellular). UniProt also lists nucleoplasm and nucleolus (UniProt Q9Y3Y2: subcellular location). This fluorescence observation informs compartment interpretation; the supplied ICC status is Supported for HPA030540, while HPA028647 has no supplied ICC status (HPA: antibody validation). |
| Situation | Likely cause | Next action |
|---|---|---|
| A listed positive population has no visible nuclear colour. | The assay may have failed, or the sampled cells may be poorly preserved (general IHC practice); HPA reports High staining for the listed populations, not a guarantee for every section (HPA: tissue IHC). | Confirm the expected cells are present, inspect the counterstain, then check retrieval, antibody application and detection with a working positive control (general IHC practice). |
| Nuclei and surrounding tissue are both dark. | Excessive detection signal or incomplete blocking or washing can obscure compartment boundaries (general IHC practice). | Compare a reagent-only control, reduce background through standard blocking and washing checks, and score only nuclei that remain separable from surrounding tissue (general IHC practice; HPA: nuclear tissue profile). |
| Colour is concentrated at cell surfaces. | A surface-dominant pattern conflicts with nuclear localisation and the absence of a transmembrane segment (UniProt Q9Y3Y2: subcellular location and topology). | Recheck cell boundaries with the counterstain and compare a negative detection control before assigning the colour to CHTOP (general IHC practice). |
| Unexpected cells stain more strongly than the listed population. | Cell identity may be misread, or cross-reactivity or endogenous detection activity may contribute (general IHC practice); HPA's listed High populations are cell-specific (HPA: tissue IHC). | Identify stained cells by morphology, inspect an appropriate negative control and repeat comparison in a listed reference population (general IHC practice; HPA: tissue IHC). |
| Fine nuclear speckles are not discernible in a chromogenic section. | Routine IHC may lack the resolution to distinguish subnuclear puncta (general IHC practice); the tissue profile reports nuclear expression, while speckle support comes from ICC-IF (HPA: tissue IHC and subcellular). | Judge IHC positivity by credible nuclear staining in the expected cells; consult the separate IF/ICC guide when speckle resolution is the experimental aim (HPA: tissue IHC and subcellular). |
| Two samples show different nuclear staining intensity. | HPA assigns High staining to particular populations and reports medium staining–RNA consistency; those summaries do not establish a quantitative scale for the samples (HPA: tissue IHC). | Score comparable cell types and controls under matched staining conditions, recording nuclear extent and intensity separately (general IHC practice). |
Experiment evidence
IHC & IF images showing CHTOP staining
A07770-2 · IHCIHC analysis of C1orf77/FOP/CHTOP using anti-C1orf77/FOP/CHTOP antibody (A07770-2). C1orf77/FOP/CHTOP was detected in a paraffin-embedded se
A07770-2 · IHCIHC analysis of C1orf77/FOP/CHTOP using anti-C1orf77/FOP/CHTOP antibody (A07770-2). C1orf77/FOP/CHTOP was detected in a paraffin-embedded se
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000160679-CHTOP/tissue/cerebral+cortex#imid_7164136
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000160679-CHTOP/tissue/colon#imid_7164054
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000160679-CHTOP/tissue/liver#imid_7164063
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000160679-CHTOP/tissue/kidney#imid_7164056
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA030540; green = CHTOP, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA030540; green = CHTOP, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CHTOP IHC & IF
🧪Run adrenal gland first and score nuclear staining in its glandular cells (HPA: High in adrenal gland glandular cells). HPA detects CHTOP in all 45 scored tissues, so there is no supported negative tissue; no-primary and isotype slides carry the negative comparison, while any unstained cells on the positive slide should retain only counterstain and should not be assumed to be a validated CHTOP-negative population (HPA: no negative tissue rows; CHTOP detected in all 45 scored tissues).
Positive control tissue: Adipose tissue (Adipocytes, HPA High)
Negative control tissue: None in HPA: CHTOP 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 CHTOP in A-431, U-251MG, U2OS, NIH 3T3, with annotated localisation: Nuclear speckles (supported) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only slide and a rabbit IgG isotype control matched to the primary antibody’s known characteristics; use CHTOP knockout material or a validated immunizing-peptide block as a biological specificity control (caption: rabbit primary antibody; standard IHC practice). Quench endogenous peroxidase before HRP/DAB detection and assess background in the adrenal gland controls (caption: peroxidase secondary and DAB; standard IHC practice).
⚠️Feasibility: No target-specific fixation window or fixation effect is reported in the supplied evidence, and the selected A07770-2 paraffin-section caption does not state a fixative (caption: fixative unreported). The demonstrated IHC preparation used heat-mediated retrieval in EDTA at pH 8.0, so use that as a starting condition and check retrieval-dependent nuclear signal (caption: EDTA retrieval at pH 8.0; UniProt Q9Y3Y2: nuclear localization). The evidence does not establish whether frozen sections or IF are easier; HPA ICC-IF supports nuclear-speckle localization, while endogenous peroxidase background is a practical consideration for the selected adrenal-gland HRP/DAB slide (HPA: nuclear speckles supported; caption: HRP/DAB; standard IHC practice).
HPA tissue IHC evidence for CHTOP
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Approved — 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 |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | High | Protein (IHC) | HPA → |
| Adrenal gland | Glandular cells | High | Protein (IHC) | HPA → |
| Appendix | Lymphoid tissue | High | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | High | Protein (IHC) | HPA → |
| Breast | Adipocytes | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| None in HPA: CHTOP is detected in all 45 scored tissues. Use a no-primary (secondary-only) and an isotype control instead. | ||||
Section 3
Advanced CHTOP IHC Tips
Troubleshoot CHTOP staining in paraffin sections by checking retrieval, nuclear localisation, controls and scoring before interpreting changes in signal.
Which retrieval conditions should I use when CHTOP staining is weak?
Start with heat-mediated antigen retrieval in EDTA at pH 8.0 for paraffin sections (datasheet A07770-2). The selected tissue image used this retrieval before incubation with 2 μg/ml catalog antibody overnight at 4°C; keep those conditions together when establishing a reference run (datasheet A07770-2). If nuclear staining remains weak, compare retrieval duration across matched sections while holding antibody concentration, detection and section processing constant (standard IHC practice). Judge any improvement by nuclear signal and preserved tissue morphology, since CHTOP is reported in the nucleus and nuclear speckles (UniProt Q9Y3Y2; HPA subcellular).
How should I handle fixation when CHTOP staining varies between sections?
Target-specific fixation sensitivity is unknown: the selected paraffin-section caption does not state a fixative, and it cannot establish how CHTOP responds to fixation (datasheet A07770-2). Record the fixative and processing history for each specimen, and compare staining only across sections prepared under matched conditions (standard IHC practice). Use the documented EDTA pH 8.0 retrieval and 2 μg/ml antibody incubation as a starting point while investigating variation (datasheet A07770-2). If signal differs between batches, examine tissue preservation and run a reference section alongside the samples before assigning the difference to CHTOP expression (standard IHC practice).
What staining pattern should count as CHTOP positive in tissue?
Score CHTOP primarily within nuclei: tissue staining is described as nuclear in most tissues, while subcellular imaging supports nuclear speckles (HPA tissue; HPA subcellular). UniProt also places CHTOP in the nucleoplasm, nucleolus and regions surrounding nuclear speckles, so a uniform nuclear appearance in chromogenic sections need not resolve these finer structures (UniProt Q9Y3Y2). Check whether DAB overlaps the counterstained nucleus rather than adjacent cytoplasm, and compare similarly processed cells within the same section (standard IHC practice). Treat strong isolated cytoplasmic staining cautiously because the reported localisation is nuclear and no transmembrane segment is annotated (UniProt Q9Y3Y2 topology).
Could an isoform or modified epitope explain uneven CHTOP staining?
CHTOP has 3 annotated isoforms and several modified residues, including phosphorylation at positions 33, 40, 49 and 64 (UniProt Q9Y3Y2). The supplied tissue caption identifies the catalog antibody and its staining workflow but does not map its epitope or establish isoform selectivity (datasheet A07770-2). If staining differs across samples, inspect the antibody’s documented immunogen and epitope information before attributing that difference to an isoform or modification (standard IHC practice). Keep retrieval and detection matched during comparisons, because a change in access to an epitope can alter chromogenic signal without demonstrating a change in protein abundance (standard IHC practice).
How can IF help assess an ambiguous CHTOP IHC pattern?
In IF/ICC, look for nuclear speckles or their surrounding regions, consistent with the supported subcellular location and the perispeckle description (HPA subcellular; UniProt Q9Y3Y2). Multiplex CHTOP with a marker for the expected cell type, such as an adipocyte marker when assessing the reported adipocyte signal, and include a nuclear counterstain (HPA tissue; standard IF practice). Choose a spectrally separated fluorophore, favouring a far-red channel when tissue autofluorescence obscures shorter wavelengths, and assess single-stain controls before interpreting overlap (standard IF practice). Because CHTOP is nuclear and lacks an annotated transmembrane segment, use permeabilisation sufficient for nuclear antibody access while checking cell morphology (UniProt Q9Y3Y2 topology; standard IF practice).
How do I reduce diffuse brown staining without losing nuclear signal?
The selected tissue image used a 10% goat-serum block, 2 μg/ml primary antibody overnight at 4°C, and peroxidase-linked detection with DAB (datasheet A07770-2). Include a no-primary control and a peroxidase-blocking step to assess nonspecific detection and endogenous enzyme activity in the chromogenic workflow (standard IHC practice). If background persists, compare antibody concentrations around the documented starting condition and keep retrieval, development and wash conditions consistent between sections (datasheet A07770-2; standard IHC practice). Preserve genuine nuclear signal when adjusting the workflow, since nuclear expression is the reported tissue pattern for CHTOP (HPA tissue).
How should I quantify CHTOP across paraffin sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the scored cell population and count cells with nuclear DAB signal, using the counterstain to locate nuclei (HPA tissue; standard IHC practice). Report the percentage of positive nuclei and, if intensity is reproducible, an H-score based on intensity categories and their cell percentages (standard IHC practice). Normalise counts to the number of evaluable nuclei in each region; if reporting positive-cell density, state the sampled area in cells per mm² (standard IHC practice). Apply the same threshold, region-selection rules and staining batch controls across samples, because HPA describes nuclear expression in most tissues and reports medium agreement between staining and RNA data (HPA tissue; standard IHC practice).
Which findings distinguish true CHTOP signal from staining artefact?
A credible CHTOP pattern is nuclear, with finer speckle-associated localisation supported by subcellular imaging; evaluate it in intact cells rather than on DAB colour alone (HPA tissue; HPA subcellular; standard IHC practice). Compare the suspected positive cells with the expected population for that specimen, such as adipocytes in adipose tissue, where high staining is reported (HPA tissue: High in adipocytes). Discount staining concentrated at section edges, in necrotic regions, or in a no-primary control, and investigate diffuse cytoplasmic signal as a possible artefact (standard IHC practice; UniProt Q9Y3Y2 localisation). Check peroxidase blocking when brown signal persists without primary antibody, since endogenous enzyme activity can mimic chromogenic staining (standard IHC practice).
Boster reagents
Best CHTOP / Chromatin target of PRMT1 protein IHC Antibodies
A07770-2 has IHC images from human paraffin sections, including breast cancer and placenta; no IF image is supplied (catalog IHC and IF image captions).
Real IHC data
Anti-C1orf77/FOP/CHTOP Antibody ®
Cat # A07770-2
A07770-2 is listed for IHC with human, monkey, mouse and rat reactivity (catalog applications and reactivity). Its IHC images show human paraffin sections of breast cancer, colorectal adenocarcinoma, laryngeal squamous cell carcinoma and placenta (A07770-2 image captions).
Which to pick: Choose A07770-2 for human paraffin-section IHC: its caption reports EDTA retrieval at pH 8.0, 2 µg/mL primary antibody and HRP/DAB detection; the fixative is unreported (A07770-2 image caption). No listed SKU has IF/ICC validation or an IF image (catalog applications and IF image captions). For other species, A07770-2 lists monkey, mouse and rat reactivity, while its depicted IHC samples are human (catalog reactivity; A07770-2 image captions).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry Q9Y3Y2 (CHTOP_HUMAN, Chromatin target of PRMT1 protein).
- Human Protein Atlas. CHTOP tissue IHC expression (reliability: Approved).
- Human Protein Atlas. CHTOP subcellular location (ICC-IF): Localized to the nuclear speckles..
- Human Protein Atlas. CHTOP antibody validation summary (2 antibodies).
- Chromatin target of protein arginine methyltransferase regulates invasion, chemoresistance, and stemness in epithelial ovarian cancer. Bioscience reports 2019 — PMC6465198.
- CHTOP in Chemoresistant Epithelial Ovarian Cancer: A Novel and Potential Therapeutic Target. Frontiers in oncology 2019 — PMC6660285.
- PubMed PMID:15498874 — UniProt-cited evidence.
- PubMed PMID:16710414 — UniProt-cited evidence.
- PubMed PMID:15489334 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CHTOP (Chromatin target of PRMT1 protein). Expected localisation Nuclear staining in most tissues (HPA tissue IHC). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet A07770-2). Validated IHC antibody: A07770-2 at 2 μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Adipose tissue (Adipocytes); 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 human breast cancer tissue; fixative not specified (datasheet A07770-2); 2. Fixation: Image fixative and duration unreported (datasheet A07770-2); 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: EDTA pH 8.0 (datasheet A07770-2); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A07770-2); 8. Primary antibody: Rabbit anti-CHTOP, 2 μg/ml (datasheet A07770-2); 9. Primary incubation: Overnight at 4 °C (datasheet A07770-2). Watch for: Fixation: Keep fixation consistent across tissue sections. (standard IHC practice; not target-specific); Caveat: Staining and RNA show medium consistency (HPA tissue IHC); Isoform / epitope: 3 isoforms; epitope differences are unknown (UniProt); Regulation: Low tissue RNA specificity (HPA tissue RNA). Evidence: UniProt Q9Y3Y2, HPA tissue IHC · Approved, HPA ICC-IF · nuclear speckles., Datasheet A07770-2, PMC6465198, PMC6660285. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CHTOP/immunohistochemistry-ihc-guide.