OPN3 / Opsin-3 · IHC design guide

Design Immunohistochemistry for OPN3

Plan OPN3 paraffin-section IHC around observed cytoplasmic tissue staining (HPA tissue IHC) and annotated membrane localization (UniProt). Use the catalog antibody at 2–5 μg/ml (datasheet), include tissue controls, and interpret staining cautiously because HPA rates its reliability as uncertain (HPA tissue IHC).

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

Immunohistochemistry protocol sheet for OPN3 (IHC for OPN3): expected localisation Cytoplasmic staining (HPA tissue IHC); membrane location annotated (UniProt), antibody A09353-3, validated IHC image, and IHC protocol steps — Printable **OPN3** IHC protocol sheet — expected localisation Cytoplasmic staining (HPA tissue IHC); membrane location annotated (UniProt), antibody A09353-3, controls and protocol steps. Open the full OPN3 IHC guide →

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OPN3 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	Cytoplasmic staining (HPA tissue IHC); membrane location annotated (UniProt)
	Staining pattern	Cytoplasmic in glandular, airway epithelial and neuronal cells (HPA tissue IHC)
	Antigen retrieval	EDTA pH 8.0 HIER, heat-mediated (datasheet A09353-3)
	Positive control ⓘ	Adrenal gland+4 more · see all
	Negative control ⓘ	Lymph node+3 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 has low consistency with RNA expression (HPA tissue IHC)
	Regulation	Basal epidermal enrichment (UniProt)
	Isoform / epitope	2 isoforms; check epitope side and isoform coverage (UniProt)

Section 1

Recommended OPN3 IHC & IF Protocols

The catalog antibody protocol (datasheet A09353-3) is accompanied by two published OPN3 IHC protocols (PMC8342238; PMC8857800).

Recommended immunohistochemistry (IHC-P) protocol parameters
Sample	Paraffin-embedded mouse brain tissue; fixative not specified (datasheet A09353-3)
Fixation	Image fixative and duration unreported (datasheet A09353-3); 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 A09353-3); 20 min, 95–100 °C (standard)
Peroxidase block	3% H2O2, 10 min, room temperature (standard)
Blocking	10% goat serum (datasheet A09353-3)
Primary antibody	Rabbit anti-OPN3, 2-5 μg/ml (datasheet A09353-3)
Primary incubation	Overnight at 4 °C (datasheet A09353-3)
Detection	HRP-conjugated secondary, DAB chromogen (datasheet A09353-3)
Counterstain	Hematoxylin, blue, dehydrate and mount (standard)
Expected result	OPN3-positive staining in glandular cells of adrenal gland (HPA tissue IHC: Medium). HPA tissue profile: General cytoplasmic expression. No signal in the no-primary control.

💡Decision noteStart with EDTA pH 8.0 heat retrieval for the catalog antibody (datasheet A09353-3). Both published protocols used pH 9.0 pressure cooker retrieval (PMC8342238; PMC8857800).

Section 2

What Is the Expected OPN3 Staining Pattern?

OPN3 is a seven-transmembrane protein annotated at the cell membrane and in the cytoplasm (UniProt Q9H1Y3 topology and subcellular location). In paraffin-section IHC, expect chiefly cytoplasmic staining in selected epithelial, glandular and neuronal cells (HPA: general cytoplasmic expression; listed medium-staining cells). Treat this as a provisional pattern: HPA rates tissue IHC reliability uncertain because antibody staining and RNA expression have low consistency (HPA: tissue IHC reliability).

What am I looking at on my slide?
Cytoplasmic chromogen in bronchial respiratory epithelium, colon glands or cerebellar Purkinje cells, with identifiable cell boundaries.	This fits the reported cellular distribution; HPA scores each example medium (HPA: bronchus, colon and cerebellum tissue IHC). Membrane accentuation is plausible from OPN3 topology, but a sharp membrane rim is not required by the reported tissue pattern (UniProt Q9H1Y3 topology; HPA: general cytoplasmic expression).
A strong, exclusively nuclear IHC signal replaces the expected cytoplasmic pattern.	Investigate an artifactual or off-target signal before scoring it as OPN3 (HPA: general cytoplasmic tissue IHC expression). HPA reports nucleoplasm in ICC/IF with uncertain confidence, so that separate assay does not establish an exclusively nuclear paraffin-section IHC pattern (HPA: subcellular ICC/IF).
The strongest chromogen appears in lymph-node germinal center cells or ovarian stromal cells.	These cells are reported as not detected by HPA tissue IHC (HPA: lymph node and ovary). Consider antibody cross-reactivity or endogenous chromogenic activity, especially if the expected cells are weak. Because overall tissue IHC reliability is uncertain, this mismatch prompts controls rather than proving the signal false (HPA: tissue IHC reliability).
Broad, hazy color covers cells and surrounding section tissue without a discernible cellular pattern.	This is background rather than an interpretable OPN3 distribution; compare it with the cell-restricted, generally cytoplasmic HPA pattern (HPA: tissue IHC profile). In chromogenic IHC, residual detection activity, insufficient blocking or overly strong primary-antibody signal can produce background; a no-primary control helps separate detection background from antibody-dependent staining.
No staining appears in a section containing an HPA-listed medium-staining cell population.	First check that the relevant cells are present and identifiable: for example, bronchial respiratory epithelium, not merely bronchial tissue (HPA: bronchus tissue IHC). A blank result may reflect assay failure or a weak sample; HPA's uncertain tissue-IHC reliability means its medium score is a reference pattern, not a guaranteed positive control (HPA: tissue IHC reliability).

💡Expected OPN3 appearanceA provisional positive is medium, chiefly cytoplasmic chromogen in the specified HPA-positive cells, such as bronchial respiratory epithelium; widespread haze or dominant staining in HPA-listed negative cells is suspect (HPA: tissue IHC profile, bronchus and listed negatives; HPA: uncertain reliability).

How each factor affects the staining
Membrane topology and compartment	OPN3 has seven transmembrane segments and is annotated at the cell membrane and in the cytoplasm (UniProt Q9H1Y3 topology and subcellular location). The tissue-IHC reference pattern is generally cytoplasmic (HPA: tissue IHC profile). Topology alone cannot predict how prominently a particular antibody will outline membranes in paraffin sections.
Epitope position	UniProt assigns extracellular and cytoplasmic stretches across the OPN3 sequence (UniProt Q9H1Y3 topology). The supplied evidence does not map an IHC antibody epitope to either side. Interpret a weak or absent signal using assay controls; do not infer an epitope-specific antigen-retrieval requirement from topology.
Isoforms and modification	UniProt lists two isoforms and glycosylation sites at residues 5 and 198 (UniProt Q9H1Y3 isoforms and glycosylation). No supplied antibody epitope or isoform-specific staining evidence establishes whether these features alter the observed IHC pattern; a stained section cannot identify an isoform from appearance alone.
Tissue-IHC evidence	HPA calls the overall tissue pattern uncertain because staining and RNA expression show low consistency; its IHC listing for CAB013682 is also uncertain (HPA: tissue IHC reliability; HPA: antibody validation). Use named positive and negative cell populations as comparison points, not definitive specificity standards.
IF/ICC: should its localisation guide this IHC call?	HPA ICC/IF supports cytosol and plasma membrane localisation, while nucleoplasm, primary cilium and basal body are uncertain (HPA: subcellular ICC/IF). HPA lists ICC support for HPA049243, whereas its tissue-IHC listing concerns CAB013682 (HPA: antibody validation); IF/ICC localisation is context, not paraffin-IHC validation.

Why is my staining missing, weak or wrong?
Situation	Likely cause	Next action
The expected epithelial or neuronal cells show no chromogen.	The selected field may lack the specific cells scored by HPA, or the chromogenic assay may have failed; HPA's medium observations are not guaranteed in every section (HPA: listed positive cells; HPA: uncertain tissue IHC reliability).	Confirm cell identity on the counterstained section and compare a section containing an HPA-listed medium-staining population processed in the same run; then review the assay's retrieval and detection controls as general IHC checks.
Color appears in the no-primary control.	Antibody-independent detection activity or nonspecific chromogen deposition can create apparent staining in chromogenic IHC.	Address endogenous detection activity and reagent background using the detection system's standard controls, then repeat the comparison. Do not score antibody-treated sections as OPN3 positive while the no-primary control has the same pattern.
Lymph-node germinal center cells stain more strongly than the candidate positive cells.	HPA reports germinal center cells as not detected; cross-reactivity or detection background is possible, although the tissue-IHC reference itself is uncertain (HPA: lymph node; HPA: tissue IHC reliability).	Compare cell morphology, the no-primary control and an HPA-listed medium-staining population in the same run (HPA: listed positives). Treat the germinal-center signal as unresolved until those comparisons support a cell-specific pattern.
Only nuclei stain in a paraffin section.	This departs from HPA's general cytoplasmic tissue-IHC profile; the uncertain nucleoplasm call comes from a separate ICC/IF assay (HPA: tissue IHC profile; HPA: subcellular ICC/IF).	Check the no-primary control and whether cytoplasmic signal is visible in an HPA-listed positive cell population (HPA: listed positives). Record nuclear-only staining separately from the provisional tissue-IHC positive pattern.
The whole section has uniform haze, obscuring cell boundaries.	General IHC possibilities include excessive primary-antibody signal, inadequate blocking or incomplete removal of detection reagents; haze does not match HPA's generally cytoplasmic, cell-associated profile (HPA: tissue IHC profile).	Compare no-primary and antibody-treated sections, review blocking and wash steps, and adjust antibody concentration only within the assay's validated range. Reassess whether the remaining signal follows the specified cell populations (HPA: listed positives).

Source: UniProt Q9H1Y3 Human Protein Atlas tissue Human Protein Atlas subcellular

Experiment evidence

IHC & IF images showing OPN3 staining

IHC analysis of OPN3 using anti-OPN3 antibody (A09353-3). OPN3 was detected in a paraffin-embedded section of mouse brain 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-OPN3 Antibody (A09353-3) overnight at 4°C. Peroxidase Conjugated Goat Anti-rabbit IgG was used as secondary antibody and incubated for 30 minutes at 37°C. The tissue section was developed using HRP Conjugated Rabbit IgG Super Vision Assay Kit (Catalog # SV0002) with DAB as the chromogen.

A09353-3 · IHCIHC analysis of OPN3 using anti-OPN3 antibody (A09353-3). OPN3 was detected in a paraffin-embedded section of mouse brain tissue. Heat media

IF analysis of OPN3 using anti-OPN3 antibody (A09353-3). OPN3 was detected in a paraffin-embedded section of mouse brain 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 5 μg/mL rabbit anti-OPN3 Antibody (A09353-3) overnight at 4°C. Cy3 Conjugated Goat Anti-Rabbit IgG (BA1032) was used as secondary antibody at 1:500 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.

A09353-3 · IFIF analysis of OPN3 using anti-OPN3 antibody (A09353-3). OPN3 was detected in a paraffin-embedded section of mouse brain tissue. Heat mediat

HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000054277-OPN3/tissue/cerebral+cortex#imid_3510792

HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000054277-OPN3/tissue/colon#imid_3510734

HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000054277-OPN3/tissue/liver#imid_3510735

HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000054277-OPN3/tissue/kidney#imid_3510736

HPA · ICC-IF SuSaHuman Protein Atlas immunofluorescence, SuSa, antibody HPA049243; green = OPN3, blue = nucleus, red = microtubules.

← swipe / scroll for more images →

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

Sample controls for OPN3 IHC & IF

🧪Run bronchus first and look for staining in respiratory epithelial cells (HPA: Medium in bronchus respiratory epithelial cells); use lymph node germinal center cells as the negative tissue comparison (HPA: Not detected). On the bronchus slide, non-epithelial cells that lack specific staining should remain at background and provide an internal reference; their OPN3-negative status is not established by the HPA row (HPA: bronchus respiratory epithelial cells Medium).

Positive control tissue: Adrenal gland (Glandular cells, HPA Medium)

Negative control tissue: Lymph node (HPA Not detected)

ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show OPN3 in SuSa, U-251MG, ASC52telo, RPTEC/TERT1, hTERT-RPE1 (serum starved), NIH 3T3, with annotated localisation: Nucleoplasm (uncertain), Cytosol (supported) (HPA subcellular).

Technical controls: Include a no-primary, secondary-only control, a rabbit isotype-matched IgG control for the rabbit primary, and OPN3 knockout material or a validated peptide-block control for specificity (A09353-3 caption: rabbit primary; standard IHC practice). For bronchus DAB staining, quench endogenous peroxidase and inspect inflammatory cells and mucus for background; assess endogenous biotin if using biotin-based detection (standard IHC practice).

⚠️Feasibility: A target-specific fixation window and the effect of fixation are unreported, and the selected-SKU paraffin-section caption does not state the fixative (A09353-3 caption). Heat-mediated EDTA retrieval at pH 8.0 is a documented starting condition, but retrieval dependency has not been established; the supplied evidence also does not show that frozen sections or IF are easier (A09353-3 caption). In bronchus, inflammatory-cell peroxidase and mucus can complicate DAB interpretation (standard IHC practice).

HPA tissue IHC evidence for OPN3

Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Uncertain — Low 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
Adrenal gland	Glandular cells	Medium	Protein (IHC)	HPA →
Appendix	Glandular cells	Medium	Protein (IHC)	HPA →
Bronchus	Respiratory epithelial cells	Medium	Protein (IHC)	HPA →
Cerebellum	Purkinje cells	Medium	Protein (IHC)	HPA →
Cerebral cortex	Neuronal cells	Medium	Protein (IHC)	HPA →

Undetected expression · recommended negative controls

Tissue	Cell type	Level	Evidence	Source
Lymph node	Germinal center cells	Not detected	Protein (IHC)	HPA →
Ovary	Ovarian stroma cells	Not detected	Protein (IHC)	HPA →
Soft tissue	Chondrocytes	Not detected	Protein (IHC)	HPA →
Vagina	Squamous epithelial cells	Not detected	Protein (IHC)	HPA →

Section 3

Advanced OPN3 IHC Tips

Troubleshoot OPN3 staining in paraffin sections by checking retrieval, antibody specificity, cell identity and compartment before comparing signal across samples.

What retrieval should I try when OPN3 staining is weak in paraffin sections?

Start with heat-mediated antigen retrieval in EDTA at pH 8.0 (datasheet A09353-3). The selected paraffin-section image used this retrieval before an overnight incubation at 4°C with 2 μg/ml antibody (caption A09353-3). If staining remains weak, compare a shorter and longer heating cycle on matched sections while holding antibody concentration and detection constant (standard IHC practice). Record section loss and background alongside signal, because stronger staining alone does not establish specificity (standard IHC practice). Confirm any apparent improvement in the expected cells and membrane or cytoplasmic compartments (UniProt Q9H1Y3 localisation; HPA tissue IHC: uncertain reliability).

How should I troubleshoot variable OPN3 staining across differently fixed specimens?

The selected image identifies a paraffin section but does not state its fixative, so OPN3-specific fixation sensitivity is unknown (caption A09353-3). Document fixative, fixation duration, processing schedule and section age for each specimen before comparing staining (standard IHC practice). Run matched sections through the same EDTA retrieval at pH 8.0, antibody concentration of 2 μg/ml and detection sequence used in the selected image (caption A09353-3). If signal differs, compare preserved morphology and background as well as OPN3-positive cells; do not attribute the difference to fixation without controlled specimens (standard IHC practice).

Is diffuse cytoplasmic OPN3 staining compatible with its expected localisation?

Cytoplasmic signal can be compatible with OPN3: UniProt reports membrane and cytoplasmic localisation, while HPA describes general cytoplasmic tissue staining (UniProt Q9H1Y3 localisation; HPA tissue IHC profile). Its 7 transmembrane segments also make membrane-associated signal plausible (UniProt Q9H1Y3 topology). Examine whether the signal follows recognizable cells and whether membrane and cytoplasmic patterns recur in matched sections, rather than judging one field alone (standard IHC practice). Treat prominent nuclear staining cautiously: HPA reports uncertain nucleoplasmic localisation in its subcellular assessment, and its tissue IHC reliability is uncertain (HPA subcellular; HPA tissue IHC reliability).

How can an unknown epitope complicate interpretation of OPN3 staining?

OPN3 has 2 annotated isoforms, but the supplied evidence does not identify this antibody’s epitope or establish which isoforms it detects (UniProt Q9H1Y3 isoforms; caption A09353-3). Its topology places residues 313–402 in the cytoplasm and residues 1–40 outside the cell (UniProt Q9H1Y3 topology). Glycosylation sites are annotated at residues 5 and 198, so epitope location matters when considering accessibility, although no site-specific staining effect is established here (UniProt Q9H1Y3 glycosylation). Obtain the immunogen or epitope information before assigning a negative stain to one isoform, and use an independent specificity control when available (standard IHC practice).

What should I check when assessing OPN3 by multiplex immunofluorescence?

For IF/ICC, pair OPN3 with a validated marker identifying the expected cell population, such as keratinocytes or melanocytes in a relevant skin specimen (UniProt Q9H1Y3 tissue specificity; standard IF practice). Choose a fluorophore channel after inspecting unstained tissue autofluorescence and single-stain controls, then check bleed-through before interpreting overlap (standard IF practice). Permeabilisation needs to match the epitope: access to the cytoplasmic 313–402 tail differs from access to the extracellular 1–40 region (UniProt Q9H1Y3 topology; standard IF practice). Because this antibody’s epitope is unspecified, establish its location before treating punctate overlap or absent signal as evidence about OPN3 distribution (caption A09353-3; standard IF practice).

How can I distinguish OPN3 signal from chromogenic IHC background?

Inspect a no-primary control alongside the stained section to identify signal from tissue, secondary reagent or detection chemistry (standard IHC practice). The selected image used a peroxidase-linked secondary reagent and DAB, so include a peroxidase block and check for residual endogenous enzyme activity (caption A09353-3; standard IHC practice). Compare background after the documented 10% goat-serum block and 2 μg/ml primary incubation before increasing antibody concentration (caption A09353-3). Diffuse deposits across unrelated cells or section edges require investigation; expected OPN3 signal should be assessed against cell identity and its membrane or cytoplasmic localisation (UniProt Q9H1Y3 localisation; standard IHC practice).

How should I quantify OPN3 staining across comparable tissue sections? ⚠ ANSWER MARKED FOR VERIFICATION

Define the cell population and tissue region before scoring, then use the same sampling rules across sections (standard IHC practice). Record the percentage of positive cells and intensity categories to calculate an H-score, or measure positive cells per mm² when cell density is the main outcome (standard IHC practice). Normalise positive counts to all evaluable cells of the specified type, or to evaluable tissue area for density, while excluding folds and necrotic regions (standard IHC practice). Report membrane and cytoplasmic staining separately if both are present, and interpret group differences cautiously because HPA rates OPN3 tissue IHC reliability as uncertain (UniProt Q9H1Y3 localisation; HPA tissue IHC reliability).

What evidence would make an OPN3-positive IHC result convincing?

Look for reproducible staining in anatomically appropriate cells, with membrane or cytoplasmic signal consistent with reported OPN3 localisation (UniProt Q9H1Y3 tissue specificity and localisation). In skin, the record reports expression in keratinocytes, melanocytes and dermal fibroblasts; in brain, HPA reports medium staining in Purkinje and cerebral cortical neuronal cells (UniProt Q9H1Y3 tissue specificity; HPA tissue IHC). Compare those patterns with no-primary and independent specificity controls, while checking for edge staining, necrosis and residual endogenous peroxidase signal (standard IHC practice). Do not treat one positive field as definitive: HPA labels its tissue IHC reliability uncertain because antibody staining has low consistency with RNA expression (HPA tissue IHC reliability).

Boster reagents

Best OPN3 / Opsin-3 IHC Antibodies

A09353-3 has IHC and IF images from mouse and rat paraffin-embedded brain sections (catalog image captions); human, mouse and rat are listed as reactive (catalog reactivity).

Real IHC data

Anti-OPN3 Antibody ®

Cat # A09353-3

View product →

A09353-3 will render with its IHC image from a mouse paraffin-embedded brain section (catalog IHC image caption). Additional IHC images show rat brain, and IF images show mouse and rat brain sections (catalog IHC and IF image captions).

Which to pick: For tissue IHC, choose the polyclonal A09353-3 (catalog antibody details): its IHC caption documents a paraffin-embedded mouse brain section, EDTA retrieval at pH 8.0 and 2 μg/ml primary antibody; the fixative is unreported (catalog IHC image caption). For IF on sections, the same SKU has mouse and rat brain images at 5 μg/ml; ICC is not listed among its tested applications (catalog IF image captions; catalog applications). For work across species, A09353-3 lists human, mouse and rat reactivity, with direct tissue images for mouse and rat (catalog reactivity; catalog image captions).

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

References

UniProt Consortium. UniProt entry Q9H1Y3 (OPN3_HUMAN, Opsin-3).
Human Protein Atlas. OPN3 tissue IHC expression (reliability: Uncertain).
Human Protein Atlas. OPN3 subcellular location (ICC-IF): Mainly localized to the nucleoplasm and cytosol. In addition localized to the plasma membrane, primary cilium and basal body..
Human Protein Atlas. OPN3 antibody validation summary (2 antibodies).
Expression of OPN3 in acral lentiginous melanoma and its associated with clinicohistopathologic features and prognosis. Immunity, inflammation and disease 2021 — PMC8342238.
Integrated analysis of the prognostic and oncogenic roles of OPN3 in human cancers. BMC cancer 2022 — PMC8857800.
Blue light-emitting diodes induce autophagy in colon cancer cells by Opsin 3. Annals of gastroenterological surgery 2018 — PMC5881358.
Expression of OPN3 in lung adenocarcinoma promotes epithelial-mesenchymal transition and tumor metastasis. Thoracic cancer 2020 — PMC6996998.
PubMed PMID:10234000 — UniProt-cited evidence.
PubMed PMID:11401433 — UniProt-cited evidence.
PubMed PMID:12242008 — UniProt-cited evidence.