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NPAS4 / Neuronal PAS domain-containing protein 4 · IHC design guide
Design Immunohistochemistry for NPAS4
Plan chromogenic NPAS4 IHC in paraffin brain sections with the catalog antibody at 1:100–1:300 (datasheet). Compare neuronal staining with controls, since the reported cytoplasmic CNS pattern has uncertain reliability (HPA tissue IHC).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
NPAS4 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 | CNS cytoplasm (HPA tissue IHC); nucleus (UniProt) | |
| Staining pattern | Cytoplasmic staining in CNS neurons and molecular-layer cells (HPA tissue IHC) | |
| Antigen retrieval | Tris-EDTA pH 9.0 HIER, 95–98 °C, 20 min (rule: nuclear antigen) | |
| Positive control | Caudate+3 more · see all | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image A02045-1) | |
| Caveat | Presumed off-target binding; tissue staining is uncertain (HPA tissue IHC) | |
| Regulation | Activity-responsive in neurons (UniProt) | |
| Isoform / epitope | 2 isoforms; epitope coverage is unresolved (UniProt) |
Section 1
Recommended NPAS4 IHC & IF Protocols
The catalog antibody’s IHC-P protocol is accompanied by published NPAS4 staining protocols for rat paraffin sections, mouse free-floating sections, and mounted sections (PMC4275263; PMC3460929; PMC13172362).
| Sample | Paraffin-embedded human brain tissue; fixative not specified (datasheet A02045-1) |
| Fixation | Image fixative and duration unreported (datasheet A02045-1); 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-NPAS4, 1:100-1:300 (datasheet A02045-1) |
| 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 | NPAS4-positive staining in neuronal cells of caudate (HPA tissue IHC: Medium). HPA tissue profile: Cytoplasmic expression in CNS. No signal in the no-primary control. |
💡Decision noteStart with pH 9.0 Tris-EDTA retrieval at 95–98 °C for 20 min (page retrieval rule; UniProt: nucleus). Compare published citrate conditions if needed (PMC4275263; PMC13172362).
Section 2
What Is the Expected NPAS4 Staining Pattern?
NPAS4 is a nuclear, non-membrane neuronal transcription factor with brain tissue specificity (UniProt Q8IUM7: nucleus, topology, tissue specificity). In paraffin sections, examine neuronal cells in brain regions reported positive by HPA (HPA tissue IHC: medium staining). Treat the compartment call as provisional: HPA describes cytoplasmic CNS staining, rates its tissue IHC reliability Uncertain, and notes presumed off-target binding (HPA tissue IHC: reliability and profile).
| Defined nuclear staining in neuronal cells of cerebral cortex, hippocampus, or caudate; some cells in the cerebellar molecular layer stain. | This fits the nuclear localization of NPAS4 and the reported positive cell populations (UniProt Q8IUM7: nucleus; HPA tissue IHC: medium staining in these regions). HPA does not verify a nuclear paraffin-section pattern, so assess specificity with controls. |
| Strong cytoplasmic staining with little or no nuclear signal. | Interpret cautiously. HPA reports cytoplasmic CNS tissue staining but rates that result Uncertain and notes presumed off-target binding; UniProt places NPAS4 in the nucleus (HPA tissue IHC: profile and reliability; UniProt Q8IUM7: nucleus). |
| Prominent staining in adipocytes, glandular cells, or hematopoietic cells. | This conflicts with HPA's undetected results for those assessed cell types (HPA tissue IHC: adipose tissue, appendix and bone marrow). Check whether signal follows a plausible cell pattern and whether control sections reveal cross-reactivity or endogenous detection activity (general IHC practice). |
| Diffuse color across cells and surrounding tissue, without recognizable nuclear boundaries. | An indistinct pattern cannot support a compartment call (general IHC interpretation). Assess the primary-antibody omission control and background from the detection system, then reassess blocking, washing and antibody concentration (general IHC practice). |
| No staining in neuronal cells of a cerebral cortex, hippocampus or caudate section. | HPA reports medium staining in these neuronal populations, but its tissue IHC assessment is Uncertain (HPA tissue IHC: positive tissues and reliability). Confirm tissue integrity and assay controls before calling NPAS4 absent; a negative slide alone cannot distinguish biology from assay failure (general IHC practice). |
💡Expected NPAS4 appearanceA provisional positive call is discernible nuclear staining in neuronal cells of an HPA-positive brain region, with approximately medium reported tissue intensity; isolated cytoplasmic staining or staining of HPA-negative cell types is suspect (UniProt Q8IUM7: nucleus; HPA tissue IHC: positive tissues, negative tissues, Uncertain reliability).
| Compartment evidence | UniProt assigns NPAS4 to the nucleus, and HPA ICC-IF approves nucleoplasm and nuclear bodies as main locations (UniProt Q8IUM7: subcellular location; HPA subcellular: approved main locations). HPA's cytoplasmic tissue IHC profile has Uncertain reliability, so reconcile any cytoplasmic chromogenic pattern with independent controls (HPA tissue IHC: profile and reliability). |
| Choice of tissue and cells | HPA reports medium staining in neuronal cells of caudate, cerebral cortex and hippocampus, and in cells of the cerebellar molecular layer (HPA tissue IHC: positive tissues). Select a documented positive population for interpretation; HPA's Uncertain reliability limits its use as a definitive specificity standard (HPA tissue IHC: reliability). |
| Antibody validation | The listed tissue IHC antibody HPA039255 is rated Uncertain, while HPA039248 has Approved ICC status and no listed IHC status (HPA antibodies: HPA039255, HPA039248). Approval in ICC does not establish paraffin IHC performance; interpret the catalog antibody's staining using its own IHC controls (general assay interpretation). |
| Isoforms and epitope coverage | UniProt lists two NPAS4 isoforms, but the supplied record gives no antibody epitope or isoform recognition data (UniProt Q8IUM7: isoforms; supplied antibody records). An unexpected negative result cannot be assigned to isoform exclusion from these sources alone. |
| IF/ICC Q: Where should NPAS4 appear? | A: HPA's approved ICC-IF main locations are nucleoplasm and nuclear bodies; nuclear membrane and vesicles are additional approved locations (HPA subcellular: ICC-IF). Those cell-image findings inform localization interpretation but do not supply a paraffin IHC protocol or resolve the Uncertain tissue IHC profile (HPA tissue IHC: reliability). |
| Situation | Likely cause | Next action |
|---|---|---|
| Cytoplasmic signal dominates the brain section. | HPA records cytoplasmic CNS staining but flags tissue IHC as Uncertain, with presumed off-target binding (HPA tissue IHC: profile and reliability). | Compare neuronal nuclear staining with control sections and an independently validated antibody when available; keep a cytoplasmic-only result provisional (UniProt Q8IUM7: nucleus; general IHC practice). |
| Color appears in HPA-negative cell populations. | Adipocytes, selected glandular cells and hematopoietic cells were not detected in the listed HPA tissues (HPA tissue IHC: negative tissues). | Check primary-antibody omission and detection controls for background or endogenous activity; then reassess antibody specificity in the affected cell type (general IHC practice). |
| Positive brain tissue shows no interpretable neuronal signal. | A negative section may reflect an assay problem; HPA reports medium staining in selected brain cells but rates the tissue result Uncertain (HPA tissue IHC: positives and reliability; general IHC practice). | Verify section quality, control performance, retrieval conditions and antibody application using the catalog antibody's IHC instructions (general IHC practice). |
| Diffuse chromogen obscures nuclear boundaries. | Excess nonspecific signal or detection background can prevent compartment assessment (general IHC practice). | Review the omission control, blocking and washes; adjust antibody concentration or detection development within the assay's validated range (general IHC practice). |
| Nuclear signal is visible but weak or uneven. | HPA reports medium tissue staining, not uniform staining of every neuronal nucleus (HPA tissue IHC: positive tissues and levels). | Score identifiable cells and compartments, compare a documented positive region processed alongside the section, and avoid treating weak fields alone as proof of absence (HPA tissue IHC: positives; general IHC practice). |
| ICC-IF localization seems clearer than chromogenic IHC. | HPA approves nuclear ICC-IF locations, whereas its tissue IHC profile remains Uncertain (HPA subcellular: main locations; HPA tissue IHC: reliability). | Record the two assay observations separately and use IHC-specific controls to judge the paraffin-section result; ICC approval alone cannot validate that result (HPA antibodies: ICC and IHC statuses; general assay interpretation). |
Experiment evidence
IHC & IF images showing NPAS4 staining
A02045-1 · IHCImmunohistochemistry analysis of paraffin-embedded human brain tissue, using NPAS4 Antibody. The picture on the right is blocked with the sy
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000174576-NPAS4/tissue/cerebral+cortex#imid_10248805
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000174576-NPAS4/tissue/colon#imid_10243475
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000174576-NPAS4/tissue/liver#imid_10243468
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000174576-NPAS4/tissue/kidney#imid_10243485
HPA · ICC-IF AF22Human Protein Atlas immunofluorescence, AF22, antibody HPA039248; green = NPAS4, blue = nucleus, red = microtubules.
HPA · ICC-IF AF22Human Protein Atlas immunofluorescence, AF22, antibody HPA039248; green = NPAS4, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for NPAS4 IHC & IF
🧪Run hippocampus first: neuronal cells show medium NPAS4 staining (HPA: Hippocampus, neuronal cells, Medium). Use adipose tissue as the negative, where adipocytes are not detected (HPA: Adipose tissue, adipocytes, Not detected); on the hippocampal slide, use cells outside the neuronal population as an internal background check, without assuming they are NPAS4-negative (HPA: Hippocampus, neuronal cells, Medium).
Positive control tissue: Caudate (Neuronal cells, HPA Medium)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show NPAS4 in AF22, SiHa, U2OS, with annotated localisation: Nucleoplasm (approved), Nuclear bodies (approved) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control and an isotype control matched to the primary antibody’s host species and immunoglobulin class (standard IHC practice). A synthesized-peptide block is a supported biological specificity control for the catalog antibody’s paraffin brain image (A02045-1 tissue-IHC caption: peptide-blocked image). For brain tissue, quench endogenous peroxidase in chromogenic IHC and assess autofluorescence if using IF (standard IHC/IF practice).
⚠️Feasibility: Paraffin-embedded human brain staining is shown for the catalog antibody, but its fixative is unreported; no target-specific fixation window or effect is supplied (A02045-1 tissue-IHC caption). Antigen-retrieval dependency is unreported, so optimize retrieval empirically for paraffin sections (A02045-1 tissue-IHC caption; standard IHC practice). The supplied evidence does not establish whether frozen sections or IF are easier; brain autofluorescence can complicate IF scoring, while nuclear signal is the expected primary localization (standard IF practice; UniProt Q8IUM7: Nucleus).
HPA tissue IHC evidence for NPAS4
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Uncertain — Pending external verification. Presumed off target binding observed and disregarded.). 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 |
|---|---|---|---|---|
| Caudate | Neuronal cells | Medium | Protein (IHC) | HPA → |
| Cerebellum | Cells in molecular layer | Medium | Protein (IHC) | HPA → |
| Cerebral cortex | Neuronal cells | Medium | Protein (IHC) | HPA → |
| Hippocampus | Neuronal cells | Medium | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Appendix | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | Not detected | Protein (IHC) | HPA → |
| Breast | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Bronchus | Respiratory epithelial cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced NPAS4 IHC Tips
Use nuclear staining, cell identity and matched controls to evaluate NPAS4 in paraffin section IHC; treat tissue staining patterns cautiously because HPA rates its IHC evidence uncertain.
How should I retrieve NPAS4 in paraffin sections when nuclear staining is weak?
Use Tris-EDTA pH 9.0 heat-induced epitope retrieval at 95–98 °C for 20 min as this page’s starting condition (page retrieval rule: nuclear antigen). Let sections cool in the retrieval buffer before washing, and keep heating and cooling consistent across comparison groups (standard IHC practice). The catalog antibody has a paraffin-embedded human brain IHC image, but its caption does not report retrieval conditions (A02045-1 caption). If nuclear signal remains weak, compare a shorter or longer heating interval on adjacent sections while holding antibody and detection conditions constant (standard IHC practice). Score nuclear signal against background and morphology rather than selecting the hottest condition solely for darker staining (UniProt Q8IUM7: nucleus; standard IHC practice).
Could fixation explain absent NPAS4 staining in my paraffin sections?
NPAS4-specific fixation sensitivity is unknown from the supplied evidence; the catalog image identifies paraffin-embedded human brain but does not state its fixative (A02045-1 caption). Record fixative, fixation duration and processing history for every section before comparing staining intensity (standard IHC practice). When possible, stain sections with different documented fixation histories in the same run using identical retrieval, antibody incubation and chromogen development (standard IHC practice). Check whether other nuclear antigens and tissue morphology are preserved before attributing a weak NPAS4 result to fixation (UniProt Q8IUM7: nucleus; standard IHC practice). Avoid assigning a preferred fixation time to NPAS4 until a controlled comparison establishes one for the specimen and antibody (standard IHC practice).
Should NPAS4 staining be nuclear or cytoplasmic in chromogenic IHC?
Prioritize staining within neuronal nuclei when assessing NPAS4, a nuclear transcription factor (UniProt Q8IUM7: nucleus and neuronal function). HPA subcellular imaging places it mainly in nucleoplasm and nuclear bodies, with additional nuclear membrane and vesicle localization (HPA subcellular). However, HPA tissue IHC describes cytoplasmic CNS staining and rates its reliability uncertain because presumed off-target binding was observed (HPA tissue IHC). Inspect a hematoxylin counterstain at high magnification so nuclear chromogen is distinguished from pigment or overlapping processes (standard IHC practice). Report nuclear and cytoplasmic patterns separately, and require an independent specificity control before treating cytoplasmic staining as NPAS4 (HPA tissue IHC: uncertain; standard IHC practice).
Can this antibody distinguish NPAS4 isoforms or an inaccessible epitope?
Two NPAS4 isoforms are listed, but the supplied catalog caption does not map the antibody epitope or establish isoform selectivity (UniProt Q8IUM7: isoforms 1 and 2; A02045-1 caption). NPAS4 contains an N-terminal bHLH domain, two PAS domains and a PAC domain, so epitope location matters when evaluating possible recognition differences (UniProt Q8IUM7: domains). The catalog brain image includes a synthesized-peptide blocking comparison, which supports competition by that peptide under the pictured conditions but cannot establish isoform specificity (A02045-1 caption; standard IHC interpretation). Ask for the immunogen sequence or epitope map before making isoform claims (standard IHC practice). If available, compare independently mapped antibodies on adjacent sections and document differences in nuclear staining (standard IHC practice).
How should I investigate NPAS4 by IF alongside this chromogenic IHC guide?
Use IF as a separate validation experiment and multiplex NPAS4 with a neuronal marker to check the expected cell type (UniProt Q8IUM7: neuronal transcription factor; standard IF practice). Select a far-red NPAS4 fluorophore and inspect unstained sections because brain tissue autofluorescence can obscure shorter-wavelength signals (standard IF practice). NPAS4 has no transmembrane segment and is nuclear, so permeabilize to reach the nuclear antigen; optimize a mild detergent treatment against nuclear morphology and background (UniProt Q8IUM7: topology and nucleus; standard IF practice). Include single-stain and no-primary controls to assess bleed-through and background in each channel (standard IF practice). The paraffin brain IHC caption does not establish IF fixation or antibody performance, so verify those conditions independently (A02045-1 caption).
What should I change when brain sections show diffuse brown background?
Run a no-primary section to distinguish detection-reagent background from signal associated with the primary antibody (standard IHC practice). For peroxidase-based DAB IHC, use a peroxidase block and examine any residual endogenous enzyme signal before changing antibody concentration (standard IHC practice). Wash thoroughly, limit chromogen development and compare a primary-antibody dilution series on adjacent sections while preserving the same retrieval conditions (standard IHC practice). Check section edges and damaged areas separately because drying or tissue damage can create misleading deposits (standard IHC practice). Since HPA rates its NPAS4 tissue IHC uncertain owing to presumed off-target binding, stronger diffuse cytoplasmic stain alone is weak evidence of target detection (HPA tissue IHC).
How can I quantify NPAS4 staining across brain sections reproducibly? ⚠ ANSWER MARKED FOR VERIFICATION
Define neuronal regions and scoring thresholds before reviewing experimental groups, then measure the percentage of NPAS4-positive neuronal nuclei or a nuclear H-score (UniProt Q8IUM7: nucleus and neuronal expression; standard IHC scoring practice). For cell counts, also report positive nuclei per mm² of viable sampled tissue and the total neuronal nuclei assessed (standard IHC scoring practice). Normalize positive counts to the number of eligible neuronal nuclei, or area-based counts to viable tissue area, using the same rule for every section (standard IHC scoring practice). Keep retrieval, imaging, counterstain and threshold settings constant across groups (standard IHC practice). Analyze cytoplasmic staining separately because the HPA tissue IHC pattern has uncertain reliability (HPA tissue IHC).
How do I decide whether a brown signal represents true NPAS4?
Favor reproducible staining in intact neuronal nuclei that agrees with NPAS4’s nuclear location and brain expression (UniProt Q8IUM7: nucleus and brain). Inspect adjacent hematoxylin-stained morphology for neuronal identity, and separate nuclear signal from cytoplasmic or extracellular deposits (standard IHC practice). Treat prominent cytoplasmic staining cautiously because HPA reports that pattern in CNS tissue yet rates the underlying IHC evidence uncertain due to presumed off-target binding (HPA tissue IHC). Exclude section-edge enhancement, necrotic regions and signal remaining in a no-primary peroxidase control from positive scoring (standard IHC practice). The catalog peptide-blocked brain image provides a useful specificity comparison, but confirm the pattern in independently processed sections (A02045-1 caption; standard IHC practice).
Boster reagents
Best NPAS4 / Neuronal PAS domain-containing protein 4 IHC Antibodies
A02045-1 has real IHC data from paraffin-embedded human brain tissue (IHC image caption: human brain) and lists IF plus Human, Mouse and Rat reactivity (catalog: applications and reactivity).
Real IHC data
Anti-NPAS4 Antibody
Cat # A02045-1
A02045-1 will render with an IHC figure from paraffin-embedded human brain tissue and a peptide-blocked comparison (IHC image caption: human brain and peptide block). It lists IHC and IF applications and Human, Mouse and Rat reactivity; no IF figure is supplied (catalog: applications, reactivity and image captions).
Which to pick: For tissue IHC, choose A02045-1: its own image shows paraffin-embedded human brain tissue, while the fixative is unreported (IHC image caption: paraffin-embedded human brain). For IF, A02045-1 is listed as an application, but ICC validation and an IF image are unreported (catalog: applications and image captions). For Mouse or Rat work, A02045-1 lists those species as reactive, although its shown IHC result is from Human tissue (catalog: reactivity; IHC image caption: human brain).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry Q8IUM7 (NPAS4_HUMAN, Neuronal PAS domain-containing protein 4).
- Human Protein Atlas. NPAS4 tissue IHC expression (reliability: Uncertain).
- Human Protein Atlas. NPAS4 subcellular location (ICC-IF): Mainly localized to the nucleoplasm and nuclear bodies. In addition localized to the nuclear membrane and vesicles..
- Human Protein Atlas. NPAS4 antibody validation summary (2 antibodies).
- The inhibitory effects of Npas4 on seizures in pilocarpine-induced epileptic rats. PloS one 2014 — PMC4275263.
- Npas4: a neuronal transcription factor with a key role in social and cognitive functions relevant to developmental disorders. PloS one 2012 — PMC3460929.
- NPAS4 refines spatial and temporal firing in CA1 pyramidal neurons. bioRxiv : the preprint server for biology 2026 — PMC13015365.
- Perineuronal nets in cerebellar nuclei neurons orchestrate social behaviour via regulation of neuronal activity in circuits innervated by the cerebellum. Translational psychiatry 2026 — PMC13172362.
- PubMed PMID:14701734 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
- PubMed PMID:16554811 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for NPAS4 (Neuronal PAS domain-containing protein 4). Expected localisation CNS cytoplasm (HPA tissue IHC); nucleus (UniProt). Antigen retrieval: Tris-EDTA pH 9.0 HIER, 95–98 °C, 20 min (rule: nuclear antigen). Validated IHC antibody: A02045-1 at 1:100-1:300 (the product's own IHC validation image is shown). Controls (HPA): positive Caudate (Neuronal cells); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human brain tissue; fixative not specified (datasheet A02045-1); 2. Fixation: Image fixative and duration unreported (datasheet A02045-1); 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-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-NPAS4, 1:100-1:300 (datasheet A02045-1); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image A02045-1); Caveat: Presumed off-target binding; tissue staining is uncertain (HPA tissue IHC); Isoform / epitope: 2 isoforms; epitope coverage is unresolved (UniProt); Regulation: Activity-responsive in neurons (UniProt). Evidence: UniProt Q8IUM7, HPA tissue IHC · Uncertain, HPA ICC-IF · Mainly localized to the nucleoplasm and nuclear bodies. In addition…, Datasheet A02045-1, PMC4275263, PMC3460929. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/NPAS4/immunohistochemistry-ihc-guide.