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FBXO21 / F-box only protein 21 · IHC design guide
Design Immunohistochemistry for FBXO21
Plan FBXO21 paraffin IHC around cytoplasmic staining and high signal in fallopian tube non-ciliated cells (HPA tissue IHC). The catalog antibody has an IHC dilution of 2–5 μg/ml (datasheet A13227-1); compare matched sections under consistent fixation (standard IHC practice).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
FBXO21 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 | General cytoplasmic staining (HPA tissue IHC) | |
| Staining pattern | Cytoplasmic signal, high in fallopian tube non-ciliated cells (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet A13227-1) | |
| Positive control | Bronchus+4 more · see all | |
| Negative control | Adipose tissue+2 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 | Staining and RNA show only medium consistency (HPA tissue IHC) | |
| Regulation | Expression regulation is unannotated (UniProt) | |
| Isoform / epitope | 2 isoforms; check epitope coverage for both (UniProt) |
Section 1
Recommended FBXO21 IHC & IF Protocols
The catalog antibody’s IHC-P protocol is accompanied by published FBXO21 IHC methods for gastric cancer (PMC7847638), clear cell renal carcinoma (PMC11909812), and rat kidney (PMC12875250).
| Sample | Paraffin-embedded human fallopian tube tissue; fixative not specified (datasheet A13227-1) |
| Fixation | Image fixative and duration unreported (datasheet A13227-1); 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 A13227-1); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A13227-1) |
| Primary antibody | Rabbit anti-FBXO21, 2-5 μg/ml (datasheet A13227-1) |
| Primary incubation | Overnight at 4 °C (datasheet A13227-1) |
| Detection | HRP-conjugated secondary, DAB chromogen (datasheet A13227-1) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | FBXO21-positive staining in ciliated cells (cell body) of bronchus (HPA tissue IHC: High). HPA tissue profile: General cytoplasmic expression, high abundance in fallopian tube. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated EDTA retrieval at pH 8.0 for the catalog antibody (datasheet: A13227-1); the cited articles do not specify retrieval conditions (PMC7847638; PMC11909812; PMC12875250).
Section 2
What Is the Expected FBXO21 Staining Pattern?
For chromogenic IHC on paraffin sections, expect predominantly cytoplasmic FBXO21 staining, with high signal reported in fallopian tube non-ciliated cells and the cell bodies of bronchial and nasopharyngeal ciliated cells (HPA: tissue IHC). HPA rates the tissue IHC pattern Approved, with medium agreement with RNA data and external verification pending (HPA: reliability). UniProt reports no signal peptide or transmembrane segment (UniProt O94952 topology).
| High cytoplasmic staining in fallopian tube non-ciliated cells. | This matches a reported strong tissue pattern and is a useful positive reference for interpreting a run (HPA: fallopian tube IHC). Compare the stained cells with tissue morphology and the run controls before scoring (general IHC practice). |
| High staining in bronchial or nasopharyngeal ciliated cell bodies. | This agrees with the cell-level IHC observations; HPA describes the overall tissue pattern as generally cytoplasmic (HPA: bronchus and nasopharynx IHC; HPA: tissue profile). A cell-body signal need not resolve the small structures seen by ICC-IF (HPA: subcellular ICC-IF; general microscopy practice). |
| Predominantly nuclear, sharply membranous, or luminal staining. | These patterns depart from the reported general cytoplasmic IHC profile and warrant an artifact check (HPA: tissue profile). UniProt supplies no signal peptide or transmembrane segment to support a secreted or membrane-spanning interpretation (UniProt O94952 topology). |
| Strong staining in HPA-undetected cells, or color across cells and tissue spaces. | Signal in adipocytes, bone marrow hematopoietic cells, or lymph-node germinal-center cells conflicts with their reported not detected patterns (HPA: tissue IHC). Widespread color may reflect cross-reactivity, endogenous detection activity, or nonspecific background; check controls (general IHC practice). |
| No signal in an otherwise interpretable fallopian tube section. | An absent result conflicts with the reported high signal in non-ciliated cells, but one negative slide cannot establish biological absence (HPA: fallopian tube IHC; general IHC practice). Review tissue preservation, run controls, and the validated staining conditions (general IHC practice). |
💡Expected FBXO21 appearanceA convincing positive is high, mainly cytoplasmic color in fallopian tube non-ciliated cells or bronchial and nasopharyngeal ciliated cell bodies; strong staining of HPA-undetected cells or tissue-wide haze calls for control review (HPA: tissue IHC; general IHC practice).
| Tissue and cell selection | Fallopian tube non-ciliated cells and bronchial or nasopharyngeal ciliated cell bodies provide reported high patterns; adipocytes, bone marrow hematopoietic cells, and lymph-node germinal-center cells are reported not detected (HPA: tissue IHC). |
| Strength of the tissue evidence | HPA calls the tissue IHC result Approved, while noting medium consistency with RNA expression and pending external verification (HPA: reliability). Treat the listed patterns as reported observations, especially when judging an unexpected specimen (HPA: reliability). |
| Antibody validation | HPA071452 is listed as Approved for IHC and ICC; its IHC status is Approved, not Enhanced (HPA: antibody validation). That supports using the catalog antibody's reported pattern as a reference without treating every stained cell as independently verified (HPA: antibody validation; HPA: reliability). |
| Protein topology and processing | UniProt records no signal peptide, propeptide, or transmembrane segment, and lists a single 1–628 chain (UniProt O94952 topology and processing). These annotations support caution with predominantly luminal or sharply membranous color; they do not identify an antibody epitope (UniProt O94952; general IHC practice). |
| Isoform interpretation | UniProt lists two isoforms, but the supplied evidence gives no epitope map or isoform-specific staining result (UniProt O94952 isoforms; HPA: antibody validation). Do not assign a slide pattern to either isoform from these records alone. |
| IF/ICC Q&A: what localisation is reported? | HPA reports mainly cytosol and centrosome, with additional primary cilium, cilium-tip, and basal-body localisation in ICC-IF (HPA: subcellular ICC-IF). Those are IF observations; the paraffin IHC tissue profile is general cytoplasmic expression (HPA: tissue IHC). |
| Situation | Likely cause | Next action |
|---|---|---|
| The fallopian tube positive reference has no visible stain. | A failed run or unsuitable assay conditions are possible; HPA reports high signal in non-ciliated cells (HPA: fallopian tube IHC; general IHC practice). | Check tissue morphology and run controls, then repeat under the catalog antibody's validated IHC conditions (general IHC practice). Target-specific fixation sensitivity is unreported in the supplied sources. |
| Color is predominantly nuclear or forms a crisp cell outline. | The distribution differs from HPA's general cytoplasmic IHC profile (HPA: tissue profile). A membrane-spanning interpretation also lacks support from the UniProt topology (UniProt O94952 topology). | Compare the same run with a reported positive tissue and appropriate detection controls; confirm the stained compartment against the counterstain (HPA: tissue IHC; general IHC practice). |
| Adipocytes or germinal-center cells stain strongly. | Those cells are reported not detected, making cross-reactivity or detection background possible explanations (HPA: tissue IHC; general IHC practice). | Check cell identity on the section and inspect a no-primary detection control before interpreting the color as FBXO21 (general IHC practice). |
| Brown color spreads across many cell types or tissue spaces. | Diffuse background can arise from nonspecific binding or endogenous detection activity in chromogenic IHC (general IHC practice). It is not the cell-restricted pattern described in the HPA positive tissues (HPA: tissue IHC). | Inspect the no-primary control; review blocking, washes, and detection conditions using the established IHC workflow (general IHC practice). |
| A weak section is being scored as FBXO21-negative. | HPA reports low staining in several cell populations, while its tissue reliability has only medium RNA agreement (HPA: tissue IHC; HPA: reliability). Weak color is therefore an uncertain basis for an absolute negative call. | Score intensity by identified cell type alongside a reported high-signal reference and run controls; record equivocal results explicitly (HPA: tissue IHC; general IHC practice). |
| An IHC slide lacks distinct centrosome or cilium-tip dots. | Those sites come from HPA ICC-IF localisation data; the tissue IHC summary describes general cytoplasmic expression (HPA: subcellular ICC-IF; HPA: tissue profile). | Judge this paraffin chromogenic result against the reported tissue cell types and cytoplasmic pattern; consult the separate IF/ICC guide for punctate localisation questions (HPA: tissue IHC; HPA: subcellular ICC-IF). |
Experiment evidence
IHC & IF images showing FBXO21 staining
A13227-1 · IHCIHC analysis of FBXO21 using anti-FBXO21 antibody (A13227-1). FBXO21 was detected in a paraffin-embedded section of human fallopian tube tis
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000135108-FBXO21/tissue/cerebral+cortex#imid_19780609
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000135108-FBXO21/tissue/colon#imid_19780535
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000135108-FBXO21/tissue/liver#imid_19780536
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000135108-FBXO21/tissue/kidney#imid_19780537
HPA · ICC-IF A-549Human Protein Atlas immunofluorescence, A-549, antibody HPA071452; green = FBXO21, blue = nucleus, red = microtubules.
HPA · ICC-IF A-549Human Protein Atlas immunofluorescence, A-549, antibody HPA071452; green = FBXO21, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for FBXO21 IHC & IF
🧪Run human fallopian tube first and expect staining in its non-ciliated cells (HPA: High in fallopian-tube non-ciliated cells; catalog antibody: paraffin-section image of human fallopian tube). Use adipose tissue as the negative specimen (HPA: Not detected in adipocytes); on the positive slide, compare stained cells with neighboring cells that remain at background, without assuming a particular neighboring cell type is negative (HPA: High in fallopian-tube non-ciliated cells).
Positive control tissue: Bronchus (Ciliated cells (cell body), HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show FBXO21 in A-549, SiHa, U2OS, ASC52telo, RPTEC/TERT1, hTERT-RPE1 (serum starved), with annotated localisation: Centrosome (approved), Cytosol (approved) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control, a concentration-matched rabbit isotype control, and an FBXO21 knockout specimen or validated peptide-block control (catalog antibody: rabbit anti-FBXO21; standard IHC practice). Quench endogenous peroxidase and check for DAB signal in the no-primary fallopian-tube section (catalog antibody: HRP/DAB detection; standard IHC practice).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected A13227-1 paraffin-section caption does not state the fixative (catalog antibody: fallopian-tube IHC caption). Heat retrieval with EDTA at pH 8.0 was used for that section, so use it as the starting condition; the evidence does not establish a retrieval dependency or show that frozen sections or IF are easier (catalog antibody: fallopian-tube IHC caption; HPA: ICC-IF subcellular images). No fallopian-tube-specific artefact is reported in the supplied evidence; inspect luminal edges and compare with the no-primary control before scoring signal (standard IHC practice).
HPA tissue IHC evidence for FBXO21
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Approved — Medium consistency between antibody staining and RNA expression data. Pending external verification.). 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 |
|---|---|---|---|---|
| Bronchus | Ciliated cells (cell body) | High | Protein (IHC) | HPA → |
| Fallopian tube | Non-ciliated cells | High | Protein (IHC) | HPA → |
| Nasopharynx | Ciliated cells (cell body) | High | Protein (IHC) | HPA → |
| Adrenal gland | Glandular cells | Medium | Protein (IHC) | HPA → |
| Appendix | Glandular cells | Medium | Protein (IHC) | HPA → |
Section 3
Advanced FBXO21 IHC Tips
Troubleshoot FBXO21 staining in paraffin sections by checking retrieval, controls, cellular localisation and scoring before interpreting chromogenic signal.
Which retrieval conditions should I start with for weak FBXO21 staining?
Use heat-mediated antigen retrieval in EDTA at pH 8.0 for paraffin-section FBXO21 IHC (datasheet A13227-1). The selected antibody produced staining in a paraffin-embedded human fallopian tube section with this retrieval method (datasheet A13227-1). If signal is weak, compare retrieval duration or, as a fallback, another buffer on adjacent sections while holding detection conditions constant (standard IHC practice). Include a known positive fallopian tube section and score its non-ciliated cells, which show high staining in the tissue profile (HPA: High in fallopian tube non-ciliated cells). Excessive retrieval can damage morphology or increase nonspecific staining, so assess tissue preservation alongside signal (standard IHC practice).
Could fixation explain weak or uneven FBXO21 staining?
Target-specific FBXO21 sensitivity to fixation is unknown because the selected paraffin-section caption does not state a fixative (datasheet A13227-1). Record the fixative and fixation duration for each specimen, then compare similarly processed sections before changing antibody conditions (standard IHC practice). Underfixation can compromise morphology, whereas prolonged fixation can reduce access to some epitopes; neither effect has been established specifically for FBXO21 (standard IHC practice). Keep the reported EDTA retrieval at pH 8.0 as the starting condition when comparing fixation histories (datasheet A13227-1). Use preserved morphology and a matched positive control to distinguish processing variation from low expression (standard IHC practice).
What staining pattern is plausible for FBXO21 in tissue sections?
Expect predominantly cytoplasmic tissue staining, with high abundance reported in fallopian tube (HPA: tissue IHC profile). Cell imaging also places FBXO21 in the cytosol and centrosome, with additional primary cilium, cilium-tip and basal-body localisation (HPA: subcellular). Small organelle-associated signals may be hard to resolve with chromogenic brightfield IHC, so assess the cell body before assigning puncta (standard IHC practice). High staining in fallopian tube non-ciliated cells and bronchial ciliated cell bodies provides cell-level reference patterns (HPA: tissue IHC). A solely membranous pattern warrants review because FBXO21 has no annotated transmembrane segment (UniProt O94952 topology).
How should I handle uncertainty about the antibody epitope and FBXO21 isoforms?
FBXO21 has 2 annotated isoforms and an F-box domain at residues 28–84 (UniProt O94952). The supplied caption establishes tissue staining for A13227-1 but does not identify its epitope or which isoforms it detects (datasheet A13227-1). Check the antibody's documented immunogen and isoform coverage before interpreting absent staining as absent total FBXO21 (standard IHC practice). FBXO21 has no annotated glycosylation or modified-residue sites in this record, which does not establish epitope accessibility after processing (UniProt O94952). If isoform specificity matters, compare independently validated reagents or orthogonal expression evidence on matched material (standard IHC practice).
How can I check the IHC pattern with multiplex IF?
Use IF as a separate localisation check and multiplex FBXO21 with a validated cell-type marker for the sampled tissue (standard IF practice). For fallopian tube, choose a marker that identifies non-ciliated cells; these cells show high FBXO21 tissue staining (HPA: High in fallopian tube non-ciliated cells). Choose fluorophores after examining tissue autofluorescence and include single-label controls to assess spectral spillover (standard IF practice). Because FBXO21 lacks a transmembrane segment and has reported cytosolic and centrosomal localisation, test permeabilisation for intracellular access; the antibody epitope's precise accessibility is unreported (UniProt O94952 topology; HPA: subcellular). Compare cell-body signal and any puncta with the chromogenic IHC pattern (standard IF practice).
What should I check when FBXO21 DAB staining is diffuse or widespread?
Start by comparing primary-antibody and no-primary sections to separate antibody-associated staining from detection background (standard IHC practice). The selected demonstration used 10% goat serum blocking, 2 μg/ml primary antibody overnight at 4°C, and peroxidase/DAB detection (datasheet A13227-1). Block endogenous peroxidase before chromogen development and inspect the no-primary control for residual colour (standard IHC practice). If background persists, titrate primary antibody and wash stringency while preserving a positive control on the same run (standard IHC practice). Evaluate whether signal follows intact cell bodies rather than damaged edges or deposits before assigning it to FBXO21 (standard IHC practice).
How should I quantify FBXO21 staining across paraffin sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the tissue compartment and eligible cell population before scoring, then apply the same definition to every section (standard IHC practice). For cell-body staining, record the percentage of positive cells and an H-score from intensity categories; for discrete positive cells, report density per mm² (standard IHC practice). Normalise counts to the number of eligible intact cells or measured viable tissue area, and keep exposure and threshold rules consistent (standard IHC practice). Report fallopian tube non-ciliated cells separately when using them as a reference population (HPA: High in fallopian tube non-ciliated cells). Record negative-control background and exclude damaged edges or necrotic regions before comparing specimens (standard IHC practice).
How do I distinguish convincing FBXO21 staining from artefact?
A credible pattern includes cytoplasmic cell-body staining in an appropriate population, such as fallopian tube non-ciliated cells (HPA: tissue IHC profile). Cytosolic and centrosomal localisation is supported by cell imaging, although fine puncta need separate confirmation in chromogenic sections (HPA: subcellular; standard IHC practice). Treat exclusively membranous staining cautiously because FBXO21 has no annotated transmembrane segment (UniProt O94952 topology). Compare suspicious colour at section edges, necrotic areas or enzyme-rich regions with a no-primary control and an endogenous-peroxidase block (standard IHC practice). The tissue IHC profile has Approved reliability with medium staining–RNA consistency and awaits external verification, so corroborate unexpected patterns independently (HPA: tissue IHC reliability).
Boster reagents
Best FBXO21 / F-box only protein 21 IHC Antibodies
The IHC-validated anti-FBXO21 antibody A13227-1 has real paraffin-section data from human fallopian tube (catalog IHC image); listed reactivity covers human, mouse and rat (catalog reactivity).
Real IHC data
Anti-FBXO21 Antibody ®
Cat # A13227-1
A13227-1 lists IHC among its applications and human, mouse and rat reactivity (catalog applications; catalog reactivity). Its own image shows human fallopian tube paraffin-section IHC with EDTA retrieval and DAB detection; no IF image is supplied (catalog IHC image; catalog IF images).
Which to pick: Choose A13227-1 for human paraffin-section IHC; its rabbit antibody has a human fallopian tube IHC image, but the fixative is unreported (catalog host; catalog IHC image). No listed SKU has IF/ICC validation or an IF image, so there is no supported IF/ICC pick (catalog applications; catalog IF images). For cross-species work, A13227-1 lists human, mouse and rat reactivity, while its displayed IHC evidence covers human tissue only (catalog reactivity; catalog IHC image).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry O94952 (FBX21_HUMAN, F-box only protein 21).
- Human Protein Atlas. FBXO21 tissue IHC expression (reliability: Approved).
- Human Protein Atlas. FBXO21 subcellular location (ICC-IF): Mainly localized to the cytosol and centrosome. In addition localized to the primary cilium, primary cilium tip and basal body..
- Human Protein Atlas. FBXO21 antibody validation summary (1 antibodies).
- Fbxo21 regulates the epithelial-to-mesenchymal transition through ubiquitination of Nr2f2 in gastric cancer. Journal of Cancer 2021 — PMC7847638.
- F-box protein FBXO21 overexpression inhibits the proliferation and metastasis of clear cell renal cell carcinoma and is closely related to the CREB pathway and tumor immune cell infiltration. Journal of translational medicine 2025 — PMC11909812.
- Comprehensive machine learning and experimental verification reveal the mechanism of action of autophagy-related genes FIZ1 and FBXO21 in acute kidney injury. PeerJ 2026 — PMC12875250.
- PubMed PMID:10531035 — UniProt-cited evidence.
- PubMed PMID:10048485 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for FBXO21 (F-box only protein 21). Expected localisation General cytoplasmic staining (HPA tissue IHC). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet A13227-1). Validated IHC antibody: A13227-1 at 2-5 μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Bronchus (Ciliated cells (cell body)); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human fallopian tube tissue; fixative not specified (datasheet A13227-1); 2. Fixation: Image fixative and duration unreported (datasheet A13227-1); 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 retrieval: EDTA pH 8.0 (datasheet A13227-1); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A13227-1); 8. Primary antibody: Rabbit anti-FBXO21, 2-5 μg/ml (datasheet A13227-1); 9. Primary incubation: Overnight at 4 °C (datasheet A13227-1). Watch for: Fixation: Keep fixation consistent across sections. (standard IHC practice; not target-specific); Caveat: Staining and RNA show only medium consistency (HPA tissue IHC); Isoform / epitope: 2 isoforms; check epitope coverage for both (UniProt); Regulation: Expression regulation is unannotated (UniProt). Evidence: UniProt O94952, HPA tissue IHC · Approved, HPA ICC-IF · Mainly localized to the cytosol and centrosome. In addition…, Datasheet A13227-1, PMC7847638, PMC11909812. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/FBXO21/immunohistochemistry-ihc-guide.