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FBL / rRNA 2'-O-methyltransferase fibrillarin · IHC design guide
Design Immunohistochemistry for FBL
Plan paraffin IHC for FBL using its observed nucleolar tissue pattern (HPA tissue IHC). This guide covers fixation consistency, chromogenic detection, and interpretation of the atlas staining caution.
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
FBL 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 | Nucleolar staining in tissue (HPA tissue IHC); nucleoplasm also annotated (UniProt) | |
| Staining pattern | General nucleolar staining; high in Bergmann glia nuclei (HPA tissue IHC) | |
| Antigen retrieval | Tris-EDTA pH 9.0 HIER, 95–98 °C, 20 min (rule: nuclear antigen) | |
| Positive control | Cerebellum+4 more · see all | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation consistent across paraffin sections (standard IHC practice; not target-specific) | |
| Caveat | Staining may reflect proteins from more than one gene (HPA tissue IHC) | |
| Regulation | Low tissue specificity; no specific regulator reported (HPA tissue IHC; UniProt) | |
| Isoform / epitope | 0 annotated isoforms; chain spans residues 1–321 (UniProt) |
Section 1
Recommended FBL IHC & IF Protocols
The catalog antibody’s IHC-P protocol is paired with three published FBL IHC protocols (PMC13038753; PMC12730408; PMC9405174).
| Sample | Tissue sections; selected-image fixative not specified (standard IHC workflow) |
| Fixation | Image fixative and duration unreported (datasheet M03178-6); 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 Tris-EDTA buffer, pH 9.0, 20 min at 95–98 °C (standard rule: nuclear 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 anti-FBL, 1:200-1:1000 (datasheet M03178-6) |
| 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 | FBL-positive staining in bergmann glia - nucleus of cerebellum (HPA tissue IHC: High). HPA tissue profile: General nucleolar expression. No signal in the no-primary control. |
💡Decision noteStart with Tris-EDTA pH 9.0 at 95–98 °C for 20 min (page antigen retrieval). Use the reported retrieval conditions when reproducing PMC9405174.
Section 2
What Is the Expected FBL Staining Pattern?
FBL localizes mainly to the nucleolar fibrillar region, with additional nucleoplasmic localization (UniProt P22087 subcellular location; HPA: subcellular ICC-IF). In paraffin sections, expect nucleolar staining in cells that express it, especially Bergmann glia in cerebellum (HPA: High in Bergmann glia nuclei; general nucleolar expression). HPA rates its tissue IHC profile Supported, with medium agreement between staining and RNA data and a caution that antibodies may target proteins from more than one gene (HPA: tissue IHC reliability).
| Discrete staining within nuclei, centered on nucleoli in Bergmann glia. | This fits the expected compartment and a documented high-staining cell population (UniProt P22087 subcellular location; HPA: High in Bergmann glia nuclei). Judge the location within identifiable cells; a stained nucleus alone does not establish that its signal is nucleolar. |
| Predominantly cytoplasmic, membranous or extracellular staining, without a nucleolar pattern. | Those compartments conflict with FBL's annotated nuclear and nucleolar location and lack of a transmembrane segment (UniProt P22087 subcellular location and topology). Treat isolated staining there as suspect; review morphology and staining controls before assigning it to FBL. |
| Strong staining appears in a cell population listed as not detected by HPA. | For example, adipocytes are listed as not detected (HPA: adipose tissue IHC). Check cell identity and whether the signal is nucleolar. Cross-reactivity or detection background is possible, particularly given HPA's caution about proteins from more than one gene (HPA: tissue IHC reliability). |
| Diffuse color covers many compartments or obscures nuclear detail. | The distribution prevents a confident FBL call because the reference pattern is nucleolar, with additional nucleoplasmic localization (HPA: subcellular ICC-IF; UniProt P22087 subcellular location). Assess a no-primary control and the detection chemistry for nonspecific staining (general IHC practice). |
| No visible signal in the expected positive cells of a cerebellum section. | Bergmann glia nuclei are reported High, so their absence of staining warrants a technical check (HPA: cerebellum IHC). First verify that the relevant cells are present and identifiable, then check primary-antibody application, retrieval and detection controls (general IHC practice). |
💡Expected FBL appearanceCall a positive result when staining is concentrated in nucleoli of identifiable cells, especially the high-staining Bergmann glia nuclei; additional nucleoplasmic signal can occur, while isolated diffuse cytoplasmic color is suspect (HPA: cerebellum IHC and subcellular ICC-IF; UniProt P22087 subcellular location).
| Subnuclear location | FBL is annotated in the nucleolar fibrillar region and nucleoplasm (UniProt P22087 subcellular location); HPA places its main ICC-IF signal in the nucleoli fibrillar center, with additional nucleoplasmic signal (HPA: subcellular ICC-IF). Interpret compartment before comparing overall stain strength. |
| Variation among tissues and cells | HPA reports general nucleolar expression and low RNA tissue specificity, yet its IHC examples range from High in Bergmann glia nuclei to Medium in several epithelial or glandular populations and Not detected in specified populations (HPA: tissue IHC). Use the named cell population for comparisons. |
| Strength of IHC evidence | The tissue profile is Supported, with medium agreement between antibody staining and RNA expression; HPA also cautions that antibodies may target proteins from more than one gene (HPA: tissue IHC reliability). A plausible nucleolar pattern still needs appropriate controls, especially for unexpected cells. |
| Protein topology and processing | UniProt lists no transmembrane segment, signal peptide or propeptide, and identifies one chain spanning residues 1–321 (UniProt P22087 topology and processing). These annotations support a nuclear interpretation but do not identify an antibody epitope or predict an antigen-retrieval condition. |
| IF/ICC Q&A: What location can corroborate an IHC result? | HPA ICC-IF shows mainly nucleoli fibrillar center, plus nucleoplasm (HPA: subcellular ICC-IF). This is a location cross-check for interpreting IHC; it does not establish identical staining intensity in paraffin sections (HPA: tissue IHC; HPA: subcellular ICC-IF). |
| Situation | Likely cause | Next action |
|---|---|---|
| Expected positive cells show no nucleolar color. | A technical failure is possible when Bergmann glia nuclei, reported High, are unstained (HPA: cerebellum IHC). | Confirm the cells in the section, then inspect retrieval, primary-antibody application, detection reagents and a suitable positive control (general IHC practice). Do not infer a target-specific fixation effect from this result. |
| The section stains mainly outside nuclei. | That distribution conflicts with the annotated nucleolar and nucleoplasmic locations (UniProt P22087 subcellular location; HPA: subcellular ICC-IF). | Check cell boundaries and counterstain, then compare a no-primary control. If extranuclear staining persists without nucleolar enrichment, treat its identity as unresolved (general IHC practice). |
| Unexpected cells stain strongly. | HPA lists some populations as Not detected and cautions about targeting proteins from more than one gene (HPA: tissue IHC and reliability); cross-reactivity is possible. | Identify the stained cell population and its compartment, compare with the relevant HPA entry, and check antibody-validation evidence before calling it FBL. |
| Color appears in a no-primary control. | Detection reagents or endogenous activity can contribute background in chromogenic IHC (general IHC practice). | Check the detection controls and, if using enzyme-based detection, its endogenous-activity blocking step; reassess the specimen before scoring FBL staining (general IHC practice). |
| Nuclear color is uniform, with no discernible nucleoli. | FBL can also occur in nucleoplasm, but its main reported location is nucleolar (UniProt P22087 subcellular location; HPA: subcellular ICC-IF). | Review nuclear morphology and counterstain, compare with a documented positive section, and avoid calling uniform nuclear color a definitive nucleolar pattern (general IHC practice). |
| An IF/ICC image and the paraffin IHC section differ in apparent intensity. | HPA's supported ICC-IF location and tissue IHC levels describe different preparations and observations (HPA: subcellular ICC-IF; HPA: tissue IHC). | Compare whether both show nucleolar enrichment in identifiable cells. Interpret intensity within each assay and its own controls rather than transferring an IF intensity expectation to IHC (general IHC practice). |
Experiment evidence
IHC & IF images showing FBL staining
M03178-6 · IHCMouse testis was stained with Anti-Fibrillarin rabbit antibody
M03178-6 · IHCRat liver was stained with anti-Fibrillarin rabbit antibody
M03178 · IHCImmunohistochemical analysis of paraffin-embedded human testis, using Fibrillarin Antibody.
M03178 · IFImmunofluorescent analysis of Hela cells, using Fibrillarin Antibody .
A03178-1 · IFIF analysis of Fibrillarin/FBL using anti-Fibrillarin/FBL antibody (A03178-1). Fibrillarin/FBL was detected in an immunocytochemical section
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000105202-FBL/tissue/cerebral+cortex#imid_576712
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000105202-FBL/tissue/colon#imid_576630
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000105202-FBL/tissue/liver#imid_576631
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000105202-FBL/tissue/kidney#imid_576632
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody CAB001514; green = FBL, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody CAB001514; green = FBL, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for FBL IHC & IF
🧪Run cerebellum first and score nucleolar staining in Bergmann glia nuclei (HPA: High in Bergmann glia nuclei). Use adipose tissue as the negative comparison, scoring adipocytes (HPA: Not detected in adipocytes); on the cerebellum slide, cells without nucleolar staining should show only background, but the supplied HPA rows do not identify a specific negative cerebellar cell type.
Positive control tissue: Cerebellum (Bergmann glia - nucleus, HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show FBL in A-431, U-251MG, U2OS, with annotated localisation: Nucleoli fibrillar center (supported) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control, a host- and isotype-matched control immunoglobulin, and FBL-knockout material as a biological negative (standard IHC controls). For chromogenic cerebellum IHC, quench endogenous peroxidase and assess background on the no-primary slide (standard IHC practice).
⚠️Feasibility: A target-specific fixation window and the effect or requirement of antigen retrieval are unreported in the supplied evidence; optimize retrieval empirically for paraffin sections. The selected M03178-6 mouse-testis IHC caption does not report a fixative (selected-SKU caption). ICC-IF images offer a nucleolar localization check (HPA: nucleoli fibrillar center, with additional nucleoplasmic localization), but the evidence does not establish whether frozen sections or tissue IF are easier, or identify a cerebellum-specific artefact.
HPA tissue IHC evidence for FBL
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Supported — 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 |
|---|---|---|---|---|
| Cerebellum | Bergmann glia - nucleus | High | Protein (IHC) | HPA → |
| Adrenal gland | Glandular cells | Medium | Protein (IHC) | HPA → |
| Appendix | Glandular cells | Medium | Protein (IHC) | HPA → |
| Breast | Glandular cells | Medium | Protein (IHC) | HPA → |
| Bronchus | Respiratory epithelial cells | Medium | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | Not detected | Protein (IHC) | HPA → |
| Liver | Cholangiocytes | Not detected | Protein (IHC) | HPA → |
| Parathyroid gland | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Smooth muscle | Smooth muscle cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced FBL IHC Tips
Use nucleolar localisation, matched controls, and consistent tissue processing to troubleshoot FBL staining in chromogenic paraffin IHC (UniProt P22087; HPA tissue IHC).
How should I adjust retrieval when nucleolar FBL staining is weak?
For paraffin IHC, start with Tris-EDTA pH 9.0 HIER at 95–98 °C for 20 min (page retrieval rule: nuclear antigen). If staining is weak, compare retrieval conditions on adjacent sections while holding antibody dilution, detection, and imaging constant (standard IHC practice). Judge improvement by discrete nucleolar staining, with possible weaker nucleoplasmic signal, rather than by overall nuclear darkness (UniProt P22087 localisation; HPA subcellular). Include a no-primary control to reveal detection background after heating (standard IHC practice). Because the supplied product caption reports staining in mouse testis but no processing details, it cannot establish a retrieval method for SKU M03178-6 (selected IHC caption).
Could fixation explain weak or diffuse FBL staining?
Target-specific fixation sensitivity is unknown from the supplied evidence, so do not assign a particular loss of FBL staining to a fixative or fixation duration (supplied evidence). The mouse testis caption for SKU M03178-6 does not state its fixative (selected IHC caption). Compare sections with documented processing histories and keep retrieval and detection conditions matched when investigating a suspected processing effect (standard IHC practice). Inspect morphology alongside staining: damaged nuclei make nucleolar scoring unreliable even when chromogen is present (standard IHC practice; UniProt P22087 localisation). Record fixation and processing for each specimen before attributing differences in staining to FBL abundance (standard IHC practice).
What compartment should convincing FBL staining occupy?
Expect predominantly discrete intranuclear nucleolar staining, with possible additional nucleoplasmic staining (UniProt P22087 localisation; HPA subcellular). The reported main location is the nucleoli fibrillar center, although routine chromogenic sections should be interpreted at the resolution actually achieved (HPA subcellular; standard microscopy practice). Compare the chromogen with a nuclear counterstain and inspect intact cells at high magnification before calling small dark structures positive (standard IHC practice). Predominantly cytoplasmic or membranous staining conflicts with the reported distribution and deserves control review (UniProt P22087 localisation). FBL has no annotated transmembrane segment, which further supports scrutinising a membrane pattern (UniProt P22087 topology).
How do epitope uncertainty and FBL modifications affect antibody selection?
The supplied record lists 0 isoforms and a 1–321 protein chain, so it provides no isoform-specific staining pattern to score (UniProt P22087). It lists multiple modified residues, including asymmetric dimethylarginines near the amino terminus, but supplies no antibody epitope for SKU M03178-6 (UniProt P22087; selected IHC caption). Therefore, a change in staining cannot be assigned to a particular modification or epitope masking mechanism from these data (supplied evidence). Check the catalog antibody's documented antigen and IHC validation before interpreting an unusual pattern (standard antibody validation practice). Use orthogonal controls where available to test whether staining tracks FBL specifically (standard IHC practice).
How should I investigate the FBL pattern with a companion IF assay?
Use IF as a companion localisation check while interpreting this page's primary result as chromogenic paraffin IHC (page application). In a suitable cerebellum specimen, multiplex FBL with a validated Bergmann glia marker to identify the cell population reported as strongly nuclear-positive (HPA: High in Bergmann glia; standard IF practice). Choose a fluorophore channel with low measured tissue autofluorescence, and include single-stain controls when assessing overlap (standard IF practice). Permeabilise sufficiently for antibody access to nuclear and nucleolar antigen, since FBL has no transmembrane segment and is reported in those compartments (UniProt P22087 topology and localisation; standard IF practice). Optimise IF staining independently of the chromogenic IHC conditions (standard assay practice).
What controls help distinguish nuclear background from FBL staining?
Run a no-primary control through the same chromogenic detection steps to identify signal from the detection system or tissue (standard IHC practice). Block endogenous peroxidase before a peroxidase-based DAB reaction, and assess whether residual pigment follows tissue structures rather than nucleoli (standard IHC practice; UniProt P22087 localisation). Titrate the catalog antibody and check wash stringency if nuclei stain uniformly or extracellular material accumulates chromogen (standard IHC practice). Keep counterstaining consistent so dark hematoxylin is not mistaken for FBL-positive nucleoli (standard IHC practice). Interpret a discrete nucleolar pattern against controls, acknowledging that weaker nucleoplasmic localisation is also reported (HPA subcellular).
How should I score FBL across sections with different cellularity? ⚠ ANSWER MARKED FOR VERIFICATION
Define the eligible cell population and score intact nuclei with discernible nucleoli before comparing specimens (standard IHC scoring practice; UniProt P22087 localisation). Report the percentage of nucleolar-positive cells and, if intensity is reproducible, an H-score based on predefined staining categories (standard IHC scoring practice). Normalise positive counts to eligible nuclei, or report positive-cell density per mm² of evaluated tissue with the area stated (standard quantitative pathology practice). Apply the same detection, counterstain, imaging, and threshold settings across the comparison (standard IHC practice). Stratify by cell type because the tissue atlas reports different staining levels among cell populations (HPA tissue IHC).
When is apparent FBL positivity more likely to be artefact?
Prioritise staining in nucleoli of intact cells, allowing for additional nucleoplasmic signal (UniProt P22087 localisation; HPA subcellular). Review a signal concentrated at section edges, in necrotic areas, or outside nuclei against morphology and controls before scoring it (standard IHC practice; UniProt P22087 localisation). Check residual endogenous peroxidase with a no-primary control when DAB signal follows tissue structures without a nucleolar pattern (standard IHC practice). Use the identified cell type as context: Bergmann glia are reported High, while adipocytes are reported Not detected in the supplied atlas (HPA tissue IHC). Treat atlas comparisons cautiously because its tissue IHC reliability is Supported and its annotation warns that the antibody targets protein from more than one gene (HPA tissue IHC).
Boster reagents
Best FBL / rRNA 2'-O-methyltransferase fibrillarin IHC Antibodies
IHC data show FBL staining in human and mouse tissue; IF/ICC data show staining in A549 cells (catalog image captions). The antibodies list human, mouse, rat, or monkey reactivity (catalog applications/reactivity).
Real IHC data
Anti-Fibrillarin Rabbit Monoclonal Antibody
Cat # M03178-6
Real IHC data
Anti-Fibrillarin FBL Rabbit Monoclonal Antibody
Cat # M03178
Real IF data
Anti-Fibrillarin/FBL Antibody ®
Cat # A03178-1
M03178-6 has IHC images of mouse testis and human, mouse, and rat liver; M03178 has an IHC image of paraffin-embedded human testis (catalog IHC captions). A03178-1 has an IF/ICC image of A549 cells (catalog IF caption).
Which to pick: For paraffin-section IHC, choose M03178: its own image shows paraffin-embedded human testis, though the fixative is unreported (M03178 IHC caption). For IF/ICC, choose A03178-1 for the demonstrated A549-cell preparation (A03178-1 IF caption; catalog applications). For tissue IHC across human, mouse, and rat, consider M03178-6, a rabbit monoclonal with IHC images across those species; its image captions do not report tissue processing or fixative (M03178-6 catalog reactivity, description, and IHC captions).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P22087 (FBRL_HUMAN, rRNA 2'-O-methyltransferase fibrillarin).
- Human Protein Atlas. FBL tissue IHC expression (reliability: Supported).
- Human Protein Atlas. FBL subcellular location (ICC-IF): Mainly localized to the nucleoli fibrillar center. In addition localized to the nucleoplasm..
- Human Protein Atlas. FBL antibody validation summary (3 antibodies).
- Low level of Fibrillarin, a ribosome biogenesis factor, is a new independent marker of poor outcome in breast cancer. BMC cancer 2022 — PMC9092774.
- TRIM21-Mediated ubiquitination of FBL suppresses PI3K/AKT signaling and tumor progression in clear cell renal cell carcinoma. Cellular and molecular life sciences : CMLS 2026 — PMC13038753.
- Fibrillarin Contributes to the Oncogenic Characteristics of Colorectal Cancer Cells and Reduces Sensitivity to 5-Fluorouracil. Cancers 2025 — PMC12730408.
- Bioinformatic Analysis and In Vitro and In Vivo Experiments Reveal That Fibrillarin Participates in the Promotion of Lung Metastasis in Hepatocellular Carcinoma. Bioengineering (Basel, Switzerland) 2022 — PMC9405174.
- PubMed PMID:1846968 — UniProt-cited evidence.
- PubMed PMID:2026646 — UniProt-cited evidence.
- PubMed PMID:19054851 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for FBL (rRNA 2'-O-methyltransferase fibrillarin). Expected localisation Nucleolar staining in tissue (HPA tissue IHC); nucleoplasm also annotated (UniProt). Antigen retrieval: Tris-EDTA pH 9.0 HIER, 95–98 °C, 20 min (rule: nuclear antigen). Validated IHC antibody: M03178-6 at 1:200-1:1000 (the product's own IHC validation image is shown). Controls (HPA): positive Cerebellum (Bergmann glia - nucleus); negative Adipose tissue. IHC workflow; specimen preparation unspecified. Protocol steps: 1. Sample: Tissue sections; selected-image fixative not specified (standard IHC workflow); 2. Fixation: Image fixative and duration unreported (datasheet M03178-6); 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 Tris-EDTA buffer, pH 9.0 , 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 anti-FBL, 1:200-1:1000 (datasheet M03178-6); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: Keep fixation consistent across paraffin sections (standard IHC practice; not target-specific); Caveat: Staining may reflect proteins from more than one gene (HPA tissue IHC); Isoform / epitope: 0 annotated isoforms; chain spans residues 1–321 (UniProt); Regulation: Low tissue specificity; no specific regulator reported (HPA tissue IHC; UniProt). Evidence: UniProt P22087, HPA tissue IHC · Supported, HPA ICC-IF · Mainly localized to the nucleoli fibrillar center. In addition…, Datasheet M03178-6, PMC13038753, PMC12730408. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/FBL/immunohistochemistry-ihc-guide.