CBX2 / Chromobox protein homolog 2 · IHC design guide

Design Immunohistochemistry for CBX2

Plan CBX2 paraffin IHC around nuclear staining in testis, where elongated or late spermatids show high signal (HPA tissue IHC). This guide covers fixation consistency, antibody dilution, chromogenic detection, and nuclear scoring.

Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use

Immunohistochemistry protocol sheet for CBX2 (IHC for CBX2): expected localisation Nuclear staining in several tissues, including testis (HPA tissue IHC), antibody A06356-2, validated IHC image, and IHC protocol steps — Printable **CBX2** IHC protocol sheet — expected localisation Nuclear staining in several tissues, including testis (HPA tissue IHC), antibody A06356-2, controls and protocol steps. Open the full CBX2 IHC guide →

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CBX2 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 several tissues, including testis (HPA tissue IHC)
	Staining pattern	Strong nuclear staining in elongated or late spermatids (HPA tissue IHC)
	Antigen retrieval	EDTA pH 8.0 HIER, heat-mediated (datasheet A06356-2)
	Positive control ⓘ	Testis
	Negative control ⓘ	Adipose tissue+4 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	Low epithelial signal may complicate scoring (HPA tissue IHC)
	Regulation	Tissue enhanced RNA: testis, lymphoid tissue (HPA RNA)
	Isoform / epitope	2 isoforms; epitope differences unspecified (UniProt)

Section 1

Recommended CBX2 IHC & IF Protocols

The catalog antibody uses EDTA pH 8.0 retrieval (datasheet: A06356-2). Two published CBX2 IHC protocols use citrate pH 6.0 (PMC12804991; PMC5403172).

Recommended immunohistochemistry (IHC-P) protocol parameters
Sample	Paraffin-embedded human the renal pelvis is squamous metaplasia tissue; fixative not specified (datasheet A06356-2)
Fixation	Image fixative and duration unreported (datasheet A06356-2); 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 A06356-2); 20 min, 95–100 °C (standard)
Peroxidase block	3% H2O2, 10 min, room temperature (standard)
Blocking	10% goat serum (datasheet A06356-2)
Primary antibody	Rabbit anti-CBX2, 2-5 μg/ml (datasheet A06356-2)
Primary incubation	Overnight at 4 °C (datasheet A06356-2)
Detection	Streptavidin-biotin complex (SABC), DAB chromogen (datasheet A06356-2)
Counterstain	Hematoxylin, blue, dehydrate and mount (standard)
Expected result	CBX2-positive staining in elongated or late spermatids of testis (HPA tissue IHC: High). HPA tissue profile: Nuclear expression in several tissues, including testis. No signal in the no-primary control.

💡Decision noteStart with heat-mediated EDTA pH 8.0 for the catalog antibody (datasheet: A06356-2); assess citrate pH 6.0 as the published alternative (PMC12804991; PMC5403172).

Section 2

What Is the Expected CBX2 Staining Pattern?

CBX2 is a nuclear chromatin protein with no transmembrane segment (UniProt Q14781: location and topology). In paraffin-section IHC, expect nuclear staining in several tissues, with high staining in testicular elongated or late spermatids (HPA: tissue IHC). The tissue profile is rated Approved, meaning external characterization supports the antibody staining (HPA: tissue IHC reliability).

What am I looking at on my slide?
Distinct nuclear staining in elongated or late spermatids, with little staining outside their nuclei.	This matches the high testis signal and nuclear tissue pattern reported by HPA (HPA: testis IHC and tissue profile). CBX2 also associates with chromatin and can form nuclear foci (UniProt Q14781: subcellular location); individual foci need not be resolved in chromogenic IHC.
Predominantly cytoplasmic or membrane staining, with absent or weak nuclear staining.	Treat this as a compartment mismatch requiring validation: CBX2 is nuclear and chromatin-associated, with no transmembrane segment (UniProt Q14781: location and topology). Review the counterstain and compare a known-positive section before interpreting the color as CBX2.
Strong staining in adipocytes or cardiomyocytes while the expected testis nuclei are negative.	This pattern conflicts with HPA's not detected calls for those cells and high call for late spermatids (HPA: adipose tissue, heart muscle and testis IHC). Cross-reactivity or endogenous chromogenic detection activity is possible; the pattern alone cannot distinguish them.
Diffuse color across nuclei, cytoplasm and empty tissue spaces.	A widespread haze cannot establish the reported nuclear pattern (HPA: tissue IHC profile; UniProt Q14781: location). General IHC-P practice: inspect the no-primary control for detection background and compare tissue structure before scoring any cell as positive.
No nuclear signal in a well-preserved testis section containing elongated or late spermatids.	This conflicts with the HPA high call for those cells (HPA: testis IHC). First confirm the relevant cells are present; then check antibody application, retrieval and chromogenic detection with appropriate controls. The supplied sources do not establish CBX2-specific retrieval or fixation sensitivity.

💡Expected CBX2 appearanceCall positive when elongated or late spermatid nuclei show high staining (HPA: testis IHC); predominant cytoplasmic or membrane color is discordant with CBX2 localization (UniProt Q14781: location and topology).

How each factor affects the staining
Nuclear and chromatin localization	CBX2 occupies the nucleus and distinct chromatin foci (UniProt Q14781: subcellular location). Score staining against identifiable nuclei; a chromogenic signal need not reveal individual foci. HPA describes nuclear expression across several tissues (HPA: tissue IHC profile).
Tissue and cell selection	Testicular elongated or late spermatids provide the clearest stated positive reference: high (HPA: testis IHC). Several epithelial or glandular populations are only low, and the listed adipocytes and cardiomyocytes are not detected (HPA: tissue IHC levels). Interpret weak fields by cell type.
Antibody validation scope	HPA023083 is Approved for IHC; the supplied antibody record does not label its IHC evidence Enhanced (HPA: antibody validation). The HPA tissue profile is also Approved, with external characterization supporting staining (HPA: tissue IHC reliability). Use the reported pattern as a reference, not proof of specificity in every specimen.
Isoforms and processing	UniProt lists 2 isoforms, one chain spanning residues 1–532, and no signal peptide or propeptide (UniProt Q14781: isoforms and processing). No isoform-specific IHC pattern or antibody epitope is supplied, so these annotations do not justify assigning different staining patterns to the isoforms.
IF/ICC Q: Where should signal appear?	A: In the nucleoplasm (HPA: supported ICC-IF localization); UniProt also describes chromatin foci (UniProt Q14781: subcellular location). This is an interpretation cue for IF/ICC; the supplied catalog validation lists ICC as Supported (HPA: antibody validation).

Why is my staining missing, weak or wrong?
Situation	Likely cause	Next action
Known-positive testis has no nuclear signal.	The section may lack the relevant spermatids, or an IHC-P step may have failed; HPA reports high staining specifically in elongated or late spermatids (HPA: testis IHC).	Confirm those cells by morphology. General IHC-P practice: check primary-antibody application, retrieval and detection controls before changing conditions; CBX2-specific retrieval sensitivity is unreported in the supplied sources.
Color is mainly cytoplasmic or outlines cell membranes.	The compartment conflicts with nuclear, chromatin-associated CBX2 and its lack of a transmembrane segment (UniProt Q14781: location and topology). Background or nonspecific binding may be responsible.	Compare with a positive testis section and a no-primary control. General IHC-P practice: inspect blocking and detection background, then score only signal convincingly associated with nuclei.
Adipocytes or cardiomyocytes stain strongly.	HPA reports CBX2 as not detected in these cell types (HPA: adipose tissue and heart muscle IHC). Cross-reactivity or endogenous chromogenic activity is possible.	Run a no-primary detection control and compare the same staining run with the HPA-positive testis cell population (HPA: testis IHC). Avoid calling this unexpected color CBX2 without further validation.
The slide shows diffuse brown haze.	A diffuse field obscures the expected nuclear pattern (HPA: tissue IHC profile). Its source cannot be identified from appearance alone.	General IHC-P practice: examine a no-primary control, check blocking and washes, and reassess antibody concentration against a positive section before scoring nuclei.
A low-expression tissue appears weak or negative.	HPA lists low staining in parathyroid glandular cells and several respiratory or squamous epithelial cell groups (HPA: tissue IHC levels). A weak result there is less decisive than loss of the reported high testis signal.	Identify the cell type and compare staining with elongated or late spermatids in a positive control (HPA: testis IHC). Do not treat a low-staining tissue alone as evidence that the IHC run failed.
Dark counterstain makes nuclear color hard to judge.	General chromogenic IHC practice: overlapping nuclear counterstain and reaction color can make localization difficult to assess.	Review a lighter-counterstained section or adjust counterstaining in a controlled repeat. Judge the result by nuclear localization and the relevant spermatid cell type (UniProt Q14781: location; HPA: testis IHC).

Source: UniProt Q14781 Human Protein Atlas tissue Human Protein Atlas subcellular

Experiment evidence

IHC & IF images showing CBX2 staining

IHC analysis of CBX2 using anti-CBX2 antibody (A06356-2). CBX2 was detected in a paraffin-embedded section of human the renal pelvis is squamous metaplasia tissue. Heat mediated antigen retrieval was performed in EDTA buffer (pH 8.0, epitope retrieval solution). The tissue section was blocked with 10% goat serum. The tissue section was then incubated with 2 μg/ml rabbit anti-CBX2 Antibody (A06356-2) overnight at 4°C. Biotinylated goat anti-rabbit IgG was used as secondary antibody and incubated for 30 minutes at 37°C. The tissue section was developed using Strepavidin-Biotin-Complex (SABC) (Catalog # SA1022) with DAB as the chromogen.

A06356-2 · IHCIHC analysis of CBX2 using anti-CBX2 antibody (A06356-2). CBX2 was detected in a paraffin-embedded section of human the renal pelvis is squa

IHC analysis of CBX2 using anti-CBX2 antibody (A06356-2). CBX2 was detected in a paraffin-embedded section of human rectum differentiated adenocarcinoma tissue. Heat mediated antigen retrieval was performed in EDTA buffer (pH 8.0, epitope retrieval solution). The tissue section was blocked with 10% goat serum. The tissue section was then incubated with 2 μg/ml rabbit anti-CBX2 Antibody (A06356-2) overnight at 4°C. Biotinylated goat anti-rabbit IgG was used as secondary antibody and incubated for 30 minutes at 37°C. The tissue section was developed using Strepavidin-Biotin-Complex (SABC) (Catalog # SA1022) with DAB as the chromogen.

A06356-2 · IHCIHC analysis of CBX2 using anti-CBX2 antibody (A06356-2). CBX2 was detected in a paraffin-embedded section of human rectum differentiated ad

IF analysis of CBX2 using anti-CBX2 antibody (A06356-2). CBX2 was detected in an immunocytochemical section of A431 cells. Enzyme antigen retrieval was performed using IHC enzyme antigen retrieval reagent (AR0022) for 15 mins. The cells were blocked with 10% goat serum. And then incubated with 5 μg/mL rabbit anti-CBX2 Antibody (A06356-2) overnight at 4°C. DyLight®488 Conjugated Goat Anti-Rabbit IgG (BA1127) was used as secondary antibody at 1:100 dilution and incubated for 30 minutes at 37°C. The section was counterstained with DAPI. Visualize using a fluorescence microscope and filter sets appropriate for the label used.

A06356-2 · IFIF analysis of CBX2 using anti-CBX2 antibody (A06356-2). CBX2 was detected in an immunocytochemical section of A431 cells. Enzyme antigen re

HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000173894-CBX2/tissue/cerebral+cortex#imid_5921520

HPA · Oral mucosaHuman Protein Atlas IHC, Oral mucosa. Source: https://www.proteinatlas.org/ENSG00000173894-CBX2/tissue/oral+mucosa#imid_5921444

HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000173894-CBX2/tissue/colon#imid_5921462

HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000173894-CBX2/tissue/liver#imid_5921455

HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA023083; green = CBX2, blue = nucleus, red = microtubules.

← swipe / scroll for more images →

Real IHC / IF data behind the staining-pattern expectations in this section.

Sample controls for CBX2 IHC & IF

🧪Run testis first: elongated or late spermatids should stain (HPA: High). Use adrenal gland glandular cells as the negative tissue (HPA: Not detected); on the testis slide, cells without specific CBX2 staining should show only background, with the expected signal assessed in nuclei (UniProt Q14781: nucleus and chromatin foci).

Positive control tissue: Testis (Elongated or late spermatids, HPA High)

Negative control tissue: Adipose tissue (HPA Not detected)

ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show CBX2 in A-431, U-251MG, U2OS, KOLF2.1J, with annotated localisation: Nucleoplasm (supported) (HPA subcellular).

Technical controls: Include no-primary (secondary-only) and host- and clonality-matched isotype controls; use CBX2 knockout tissue or cells as a biological negative where available (standard IHC practice). For the testis slide, block endogenous peroxidase and check endogenous biotin background because the selected IHC caption uses a biotinylated secondary, streptavidin-biotin detection, and DAB (selected A06356-2 IHC caption).

⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected A06356-2 tissue-IHC caption does not state a fixative (selected A06356-2 IHC caption). That paraffin-section example uses heat-mediated EDTA retrieval at pH 8.0, but whether CBX2 detection depends on that retrieval condition is unreported (selected A06356-2 IHC caption). The supplied evidence does not establish that frozen sections or IF are easier; assess testis background alongside the specific nuclear signal (HPA: High in elongated or late spermatids; UniProt Q14781: nucleus and chromatin foci).

HPA tissue IHC evidence for CBX2

Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Approved — External characterization data supports antibody staining.). 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
Testis	Elongated or late spermatids	High	Protein (IHC)	HPA →

Undetected expression · recommended negative controls

Tissue	Cell type	Level	Evidence	Source
Adipose tissue	Adipocytes	Not detected	Protein (IHC)	HPA →
Adrenal gland	Glandular cells	Not detected	Protein (IHC)	HPA →
Caudate	Glial cells	Not detected	Protein (IHC)	HPA →
Cerebellum	Cells in granular layer	Not detected	Protein (IHC)	HPA →
Cerebral cortex	Endothelial cells	Not detected	Protein (IHC)	HPA →

Section 3

Advanced CBX2 IHC Tips

Troubleshoot CBX2 staining in paraffin sections by checking retrieval, nuclear localisation, controls, and scoring before interpreting chromogenic signal.

How should I adjust retrieval when nuclear CBX2 staining is weak?

Start with heat-mediated retrieval in EDTA at pH 8.0 (datasheet A06356-2). The catalog antibody produced staining in a paraffin section after that retrieval, followed by 2 μg/ml primary antibody overnight at 4°C (datasheet A06356-2). If nuclear staining remains weak, vary heating time or try another retrieval buffer on adjacent sections while keeping antibody concentration and detection constant; changes in staining alone do not establish specificity. Compare a testis section, where elongated or late spermatids stained strongly, with an adipose section, where adipocytes were not detected (HPA: High in elongated or late spermatids; Not detected in adipocytes).

Could fixation be responsible for weak or patchy CBX2 staining?

Target-specific fixation sensitivity is unknown: the catalog image identifies a paraffin section but does not state its fixative (datasheet A06356-2). Record the fixative, fixation duration, and processing history for each specimen, then compare sections with matched retrieval and staining conditions. If staining varies across samples, inspect tissue preservation and compare nuclear signal in intact regions before changing primary antibody concentration; overfixation and poor preservation can affect antigen accessibility in routine IHC. Avoid attributing a difference to CBX2-specific fixation sensitivity without a controlled comparison, and retain the documented EDTA pH 8.0 retrieval as the starting condition (datasheet A06356-2).

What staining pattern should count as CBX2 in a paraffin section?

Score signal in nuclei: CBX2 is annotated in the nucleus and at chromatin foci, including chromocenters (UniProt Q14781: subcellular location). A nucleoplasmic pattern is also supported by cell imaging, while tissue IHC reports nuclear expression in several tissues (HPA: Nucleoplasm supported; nuclear expression in several tissues). Use a nuclear counterstain to check whether chromogen lies within intact nuclei, and assess discrete foci only where section quality permits that distinction. Treat predominantly diffuse cytoplasmic or extracellular staining as a reason to review background and specificity, rather than counting it as positive solely because the tissue appears dark (UniProt Q14781: nuclear and chromosomal localisation).

Could isoforms or epitope placement explain inconsistent CBX2 staining?

CBX2 has 2 annotated isoforms and a chromodomain at residues 12–70 (UniProt Q14781: isoforms and domains). The supplied catalog caption does not identify the antibody epitope, so it cannot establish whether both isoforms are recognised (datasheet A06356-2: epitope not stated). Modifications annotated at residue 247 and phosphoserine 302 provide possible sites to investigate if an independently mapped epitope overlaps them; they do not establish a staining effect here (UniProt Q14781: modified residues). When staining differs between specimens, check the antibody's epitope documentation and compare an independent antibody or orthogonal expression evidence before assigning the difference to an isoform.

How can IF help resolve an ambiguous chromogenic CBX2 pattern?

Use IF on a matched specimen to ask whether CBX2 signal overlaps nuclei and the expected cell population; nuclear or chromatin localisation is annotated for CBX2 (UniProt Q14781: subcellular location). If examining testis, multiplex with an independently validated marker of elongated or late spermatids, the strongly stained population in tissue IHC (HPA: High in elongated or late spermatids). Select a fluorophore channel with low tissue autofluorescence, include single-colour and no-primary controls, and use sufficient permeabilisation for antibody access to the nuclear epitope. Optimise IF fixation and permeabilisation separately: the supplied paraffin-section caption reports neither IF conditions nor a fixative (datasheet A06356-2).

How do I reduce diffuse or speckled background without losing nuclear signal?

First inspect a no-primary section and the nuclear counterstain to separate detection-system deposits from signal inside intact nuclei; CBX2 is expected in nuclei (UniProt Q14781: subcellular location). The reported paraffin workflow used 10% goat serum, 2 μg/ml primary overnight at 4°C, a biotinylated secondary, and DAB detection (datasheet A06356-2). For excessive background, titrate primary antibody and strengthen washing one variable at a time, while retaining a known positive section. Include an endogenous peroxidase block for chromogenic IHC and evaluate possible endogenous biotin with the reported avidin–biotin detection system; these are general workflow controls, not evidence of CBX2 expression.

How should I quantify heterogeneous nuclear CBX2 staining? ⚠ ANSWER MARKED FOR VERIFICATION

Define the tissue compartment and count only interpretable nuclei, because CBX2 is annotated as nuclear or chromatin associated (UniProt Q14781: subcellular location). Report the percentage of positive nuclei and, if intensity is reproducible across a matched staining run, an H-score calculated from the percentages at each intensity level. For spatial comparisons, report positive nuclei per mm² of viable tissue and normalise to the total number of eligible nuclei in that compartment. Set thresholds using the same counterstain, exposure or scanning settings, and negative controls across sections; note that HPA reports high staining in elongated or late spermatids but no detection in adipocytes (HPA: tissue IHC).

How can I distinguish true CBX2 signal from staining artefacts?

Give greatest weight to staining within intact nuclei in an appropriate cell population; CBX2 is nuclear and chromatin associated, and HPA reports high staining in elongated or late spermatids (UniProt Q14781: subcellular location; HPA: testis IHC). Diffuse cytoplasmic deposits, stained extracellular material, or signal confined to section edges warrant review against a no-primary control and neighbouring intact tissue. Exclude necrotic regions from scoring, and check endogenous peroxidase activity when DAB remains visible without primary antibody; the catalog workflow uses DAB (datasheet A06356-2). A positive-looking section alone does not prove specificity: compare the expected compartment and controls, including adipocytes reported as not detected (HPA: adipose tissue IHC).

Boster reagents

Best CBX2 / Chromobox protein homolog 2 IHC Antibodies

A06356-2 has IHC images from human paraffin sections and mouse testis, plus an IF image from A431 cells (A06356-2 image captions).

Real IHC data

Anti-CBX2 Antibody ®

Cat # A06356-2

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A06356-2 has IHC images from human renal pelvis squamous metaplasia, rectum differentiated adenocarcinoma, and placenta, and from mouse testis (A06356-2 IHC captions). The same SKU is listed for ICC and IF, with an IF image from A431 cells (catalog: applications; A06356-2 IF caption).

Which to pick: Choose A06356-2 for paraffin-section tissue IHC; its own captions document those human and mouse samples, and the listed IHC concentration is 2–5 μg/ml (A06356-2 IHC captions; catalog: IHC dilution). For IF/ICC, A06356-2 is listed at 5 μg/ml and has an A431-cell IF image (catalog: applications and IF dilution; A06356-2 IF caption). It is listed as reactive with human and mouse and has a rabbit host; clonality and the fixative used for its IHC images are unreported (catalog: reactivity, host, clone; A06356-2 IHC captions).

Each figure is that product's own IHC / IF validation image from its datasheet.

References

UniProt Consortium. UniProt entry Q14781 (CBX2_HUMAN, Chromobox protein homolog 2).
Human Protein Atlas. CBX2 tissue IHC expression (reliability: Approved).
Human Protein Atlas. CBX2 subcellular location (ICC-IF): Localized to the nucleoplasm..
Human Protein Atlas. CBX2 antibody validation summary (1 antibodies).
CBX2 promoted oral squamous cell carcinoma via increasing CEP55/NF-κB/METTL3/SHP2 signaling induced metastasis/proliferation and angiogenesis. Scientific reports 2025 — PMC12804991.
CBX2 is a functional target of miRNA let-7a and acts as a tumor promoter in osteosarcoma. Cancer medicine 2019 — PMC6639449.
CBX2 promotes cervical cancer cell proliferation and resistance to DNA-damaging treatment via maintaining cancer stemness. The Journal of biological chemistry 2025 — PMC11835617.
Chromobox homolog 2 protein: A novel biomarker for predicting prognosis and Taxol sensitivity in patients with breast cancer. Oncology letters 2017 — PMC5403172.
PubMed PMID:16625196 — UniProt-cited evidence.
PubMed PMID:15489334 — UniProt-cited evidence.
PubMed PMID:7782071 — UniProt-cited evidence.