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ATG9A / Autophagy-related protein 9A · IHC design guide
Design Immunohistochemistry for ATG9A
Plan chromogenic ATG9A IHC on paraffin sections using the 2 μg/mL condition shown for catalog antibody A03757-3 (datasheet). Compare cytoplasmic staining with tissue examples while accounting for the HPA profile’s pending external verification (HPA tissue IHC).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
ATG9A 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 tissue staining (HPA tissue IHC) | |
| Staining pattern | Cytoplasmic staining across several tissue cell types (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet A03757-3) | |
| Positive control | Adrenal gland+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); Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image A03757-3) | |
| Caveat | Tissue staining awaits external verification (HPA tissue IHC) | |
| Regulation | Starvation redistributes ATG9A to PAS (UniProt) | |
| Isoform / epitope | 3 isoforms; epitope map unknown across cytoplasmic and luminal regions (UniProt) |
Section 1
Recommended ATG9A IHC & IF Protocols
Compare the catalog antibody’s IHC-P protocol (datasheet A03757-3) with four published ATG9A IHC workflows (PMC4076416; PMC9296391; PMC10520003; PMC12314380).
| Sample | Paraffin-embedded human glioma tissue; fixative not specified (datasheet A03757-3) |
| Fixation | Image fixative and duration unreported (datasheet A03757-3); 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 A03757-3); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A03757-3) |
| Primary antibody | Rabbit anti-ATG9A, 2-5μg/ml (datasheet A03757-3) |
| Primary incubation | Overnight at 4 °C (datasheet A03757-3) |
| Detection | Streptavidin-biotin complex (SABC), DAB chromogen (datasheet A03757-3) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | ATG9A-positive staining in glandular cells of adrenal gland (HPA tissue IHC: Medium). HPA tissue profile: Cytoplasmic expression in several tissues. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated EDTA pH 8.0 retrieval for the catalog antibody (datasheet A03757-3). Citrate pH 6.0 was used with a different antibody (PMC10520003).
Section 2
What Is the Expected ATG9A Staining Pattern?
ATG9A is a membrane protein that cycles mainly between the trans-Golgi network and endosomal system (UniProt Q7Z3C6 localization; UniProt Q7Z3C6 topology). In paraffin-section IHC, expect cytoplasmic staining in selected glandular and respiratory epithelial cells, among other reported sites (HPA tissue IHC). Treat intensity and distribution as provisional: HPA describes its tissue IHC reliability as Uncertain, pending external verification (HPA tissue IHC).
| Cytoplasmic staining in adrenal or duodenal glandular cells, or bronchial respiratory epithelium. | These are reported Medium-staining cell populations (HPA tissue IHC). A granular or perinuclear component is compatible with ATG9A trafficking through the trans-Golgi network and endosomes (UniProt Q7Z3C6 localization). Chromogenic IHC may not resolve individual vesicles (general IHC practice). |
| Predominantly nuclear staining, especially without a matching cytoplasmic pattern. | A nuclear-dominant result does not match the reported cytoplasmic tissue profile or membrane-associated locations (HPA tissue IHC; UniProt Q7Z3C6 localization). Review the staining against a control section before interpreting it as ATG9A; the location alone cannot identify the source of artefact (general IHC practice). |
| Strong staining in a cell population reported as Not detected, such as adipocytes in adipose tissue. | That result conflicts with the specified HPA cell-level observation (HPA tissue IHC). Cross-reactivity or endogenous chromogenic activity is possible (general IHC practice). HPA tissue IHC is Uncertain, so investigate the discrepancy with controls rather than treating the reference image as an absolute negative (HPA tissue IHC). |
| Diffuse color across cells and surrounding tissue, with little separation between compartments. | This obscures the reported cytoplasmic pattern (HPA tissue IHC). Broad background can reflect nonspecific antibody binding, detection reagent activity, or inadequate washing (general IHC practice). Compare the primary-antibody omission control and inspect whether the apparent signal tracks tissue structures or spreads uniformly (general IHC practice). |
| No staining in adrenal or duodenal glandular cells, or bronchial respiratory epithelium. | Each is listed as Medium in HPA tissue IHC (HPA tissue IHC). Check whether the expected cell population is present and whether the run controls worked (general IHC practice). An absent result could reflect assay performance or biological variation; HPA labels its tissue IHC reliability Uncertain (HPA tissue IHC). |
💡Expected ATG9A appearanceA plausible positive is cytoplasmic chromogenic staining in HPA-reported cells, such as Medium-staining adrenal glandular cells; a nuclear-dominant or tissue-wide diffuse result needs control-based review (HPA tissue IHC; UniProt Q7Z3C6 localization; general IHC practice).
| Cell population and reference strength | HPA reports Medium staining in selected glandular, respiratory epithelial, and neural compartments, but Not detected in specified populations including adipocytes and alveolar cells (HPA tissue IHC). Score the named cells within each tissue, since an entire organ is not uniformly positive or negative (HPA tissue IHC). |
| Membrane location and trafficking | ATG9A has four annotated transmembrane segments and chiefly cycles between the trans-Golgi network and endosomal system (UniProt Q7Z3C6 topology; UniProt Q7Z3C6 localization). These facts support a cytoplasmic compartment interpretation, but they do not establish which epitope a particular antibody detects (UniProt Q7Z3C6 topology). |
| Condition-dependent redistribution | Amino acid starvation or rapamycin can redistribute ATG9A toward the phagophore assembly site, while only a small portion transiently occupies autophagic membranes during induction (UniProt Q7Z3C6 localization). This may affect punctate patterns in experimental models; it is not a basis for assigning an autophagy state from routine tissue IHC alone (UniProt Q7Z3C6 localization). |
| Validation limits across methods | HPA rates the listed antibody HPA059551 Uncertain for IHC and Supported for ICC, and calls its tissue IHC profile Uncertain (HPA antibody validation; HPA tissue IHC). HPA ICC-IF localizes ATG9A to vesicles, but that result does not independently validate a chromogenic tissue pattern (HPA subcellular ICC-IF; HPA antibody validation). |
| Situation | Likely cause | Next action |
|---|---|---|
| Expected cytoplasmic staining is absent in a Medium-staining reference population. | The target cells may be missing from the section, or the IHC run may have failed (HPA tissue IHC; general IHC practice). | Confirm cell identity and inspect the run control; review the validated antibody's own IHC-P instructions for retrieval and dilution (general IHC practice). Do not infer an ATG9A-specific fixation effect from HPA staining levels (HPA tissue IHC). |
| Signal is predominantly nuclear. | The compartment conflicts with reported cytoplasmic tissue staining and membrane localization (HPA tissue IHC; UniProt Q7Z3C6 localization). | Compare the result with a primary-antibody omission control and a reported cytoplasmic reference population; reassess specificity if the nuclear pattern persists (general IHC practice; HPA tissue IHC). |
| A reported Not detected population stains strongly. | Cross-reactivity or endogenous chromogenic activity may contribute (general IHC practice); HPA's negative observation has Uncertain overall IHC reliability (HPA tissue IHC). | Check an omission control and the exact cell population named by HPA before calling the tissue positive; use independent validation if the discrepancy matters to the study (general IHC practice; HPA tissue IHC). |
| Color is diffuse across the section. | Nonspecific binding, detection background, or inadequate washing may mask cellular contrast (general IHC practice). | Inspect omission and run controls, then review blocking, detection, washing, and primary-antibody conditions under the chosen IHC workflow (general IHC practice). Reassess whether cytoplasmic signal separates from background (HPA tissue IHC). |
| Puncta are hard to distinguish in chromogenic tissue IHC. | ATG9A occupies vesicle-related compartments, but section thickness and chromogenic resolution can blur small structures (UniProt Q7Z3C6 localization; general IHC practice). | Score the broader cytoplasmic distribution and the correct cell type first (HPA tissue IHC). Do not require countable vesicles for a positive chromogenic result (general IHC practice). |
| IF/ICC Q: Should ATG9A appear in vesicles? | HPA reports a supported vesicular main location in ICC-IF, while the listed antibody's IHC status is Uncertain (HPA subcellular ICC-IF; HPA antibody validation). | IF/ICC A: Vesicular localization is supported for ICC-IF (HPA subcellular ICC-IF). Interpret it within an IF/ICC design; it does not by itself validate paraffin-section IHC staining (HPA antibody validation). |
Experiment evidence
IHC & IF images showing ATG9A staining
A03757-3 · IHCIHC analysis of ATG9A using anti-ATG9A antibody (A03757-3). ATG9A was detected in paraffin-embedded section of human glioma tissue. Heat med
A03757-3 · IHCIHC analysis of ATG9A using anti-ATG9A antibody (A03757-3). ATG9A was detected in paraffin-embedded section of human grastric cancer tissue.
A03757 · IHCImmunohistochemistry of ATG9A in human heart tissue with ATG9A antibody at 5 μg/mL.
A03757 · IFImmunofluorescence of ATG9A in human heart tissue with ATG9A antibody at 20 μg/mL.
M03757 · IHCImmunohistochemical analysis of paraffin-embedded human lung cancer, using ATG9A Antibody.
M03757 · IFImmunofluorescent analysis of Hepg2 cells, using ATG9A Antibody.
A03757-2 · IFIF analysis of ATG9A using anti-ATG9A antibody (A03757-2). ATG9A was detected in immunocytochemical section of A549 cells. Enzyme antigen re
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000198925-ATG9A/tissue/cerebral+cortex#imid_16372363
HPA · StomachHuman Protein Atlas IHC, Stomach. Source: https://www.proteinatlas.org/ENSG00000198925-ATG9A/tissue/stomach+1#imid_16372255
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000198925-ATG9A/tissue/colon#imid_16372289
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000198925-ATG9A/tissue/liver#imid_16372274
HPA · ICC-IF Hep-G2Human Protein Atlas immunofluorescence, Hep-G2, antibody HPA059551; green = ATG9A, blue = nucleus, red = microtubules.
HPA · ICC-IF Hep-G2Human Protein Atlas immunofluorescence, Hep-G2, antibody HPA059551; green = ATG9A, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for ATG9A IHC & IF
🧪Run bronchus first and expect staining in respiratory epithelial cells (HPA: Medium in bronchus respiratory epithelial cells). Use adipose tissue adipocytes as the negative comparator (HPA: Not detected in adipocytes); on the bronchus slide, adjacent non-epithelial cells should show only background signal, but they are not established target-negative cells by the supplied HPA rows.
Positive control tissue: Adrenal gland (Glandular cells, HPA Medium)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show ATG9A in Hep-G2, MCF-7, U2OS, Sperm, with annotated localisation: Vesicles (supported) (HPA subcellular).
Technical controls: Include no-primary (secondary-only) and species-matched rabbit isotype controls, with isotype matched to the primary antibody’s clonality if known, and an ATG9A-knockout biological control where available (caption: rabbit primary; standard IHC practice). Quench endogenous peroxidase and check for endogenous biotin background when using the caption’s biotin-based DAB detection (caption: biotinylated secondary and DAB; standard IHC practice).
⚠️Feasibility: No target-specific fixation window or fixation effect is reported, and the selected-SKU paraffin-section caption does not state the fixative (selected-SKU caption: fixative unreported). Heat retrieval in EDTA at pH 8.0 was used in the glioma example, but a retrieval dependency is not established (selected-SKU caption: EDTA retrieval). The supplied evidence does not establish that frozen sections or IF are easier; IF/ICC can assess vesicular localisation separately, while respiratory epithelial mucus warrants attention as a possible source of nonspecific background in bronchus IHC (HPA: vesicles supported; standard IHC practice).
HPA tissue IHC evidence for ATG9A
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Uncertain — Pending external verification.). Rows are taken directly from the HPA tissue chart — click any row's HPA link to view the source.
Positive expression · recommended positive controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adrenal gland | Glandular cells | Medium | Protein (IHC) | HPA → |
| Appendix | Glandular cells | Medium | Protein (IHC) | HPA → |
| Bronchus | Respiratory epithelial cells | Medium | Protein (IHC) | HPA → |
| Cerebellum | Cells in granular layer | Medium | Protein (IHC) | HPA → |
| Cerebral cortex | Neuropil | 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 → |
| Breast | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Caudate | Glial cells | Not detected | Protein (IHC) | HPA → |
| Cervix | Glandular cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced ATG9A IHC Tips
Troubleshoot ATG9A staining in paraffin sections by checking retrieval, staining controls, vesicular localisation and the cells being scored (datasheet A03757-3; UniProt Q7Z3C6; HPA tissue IHC).
What should I check when ATG9A staining is weak after antigen retrieval?
Use heat-mediated antigen retrieval in EDTA at pH 8.0 for this paraffin-section assay (datasheet A03757-3). Keep the heating and cooling cycle consistent across slides, and include a section that stained successfully in an earlier run (standard IHC practice). If signal remains weak, check section integrity, primary-antibody incubation and detection before changing retrieval conditions (standard IHC practice); the selected caption used 2 µg/ml primary antibody overnight at 4°C (A03757-3 IHC caption). If you test another retrieval condition, compare matched sections side by side and assess both signal and tissue damage (standard IHC practice).
Could fixation explain inconsistent ATG9A staining across paraffin sections?
The selected paraffin-section glioma caption does not report its fixative, so ATG9A-specific fixation sensitivity is unknown (A03757-3 IHC caption). Record fixation and processing conditions for each specimen, and compare sections with similar processing histories when troubleshooting uneven staining (standard IHC practice). If matched specimens are available, vary fixation while holding retrieval in EDTA at pH 8.0 and the other staining steps constant (datasheet A03757-3; standard IHC practice). Assess tissue preservation alongside staining intensity: damaged morphology can make apparent differences in ATG9A signal difficult to interpret (standard IHC practice). Do not infer fixation tolerance from expression patterns or protein topology alone (HPA tissue IHC; UniProt Q7Z3C6 topology).
Where should convincing ATG9A staining appear in tissue sections?
Look for cytoplasmic staining with a vesicular or perinuclear component: ATG9A mainly cycles between the trans-Golgi network and endosomal system (UniProt Q7Z3C6 subcellular location). A vesicular location is supported in cell imaging, while tissue IHC reports cytoplasmic expression across several tissues (HPA subcellular; HPA tissue IHC). Under amino acid starvation or rapamycin treatment, ATG9A can redistribute toward the phagophore assembly site, but only a small portion transiently reaches autophagic membranes (UniProt Q7Z3C6 subcellular location). In chromogenic sections, interpret apparent puncta alongside cell morphology and a no-primary control, since fine vesicles may be hard to resolve by routine IHC (standard IHC practice).
How can epitope location affect interpretation of ATG9A IHC?
ATG9A has 3 annotated isoforms and 4 transmembrane segments, with both cytoplasmic and lumenal regions (UniProt Q7Z3C6 isoforms and topology). Check the catalog antibody's immunogen coordinates before assuming that it detects every isoform or that its epitope faces the cytoplasm (standard IHC practice; UniProt Q7Z3C6 topology). The annotated glycosylation site is at residue 99 in a lumenal region, but the supplied evidence does not establish whether it affects this antibody (UniProt Q7Z3C6 topology and glycosylation). If staining differs across samples, compare matched controls and processing records before attributing the difference to isoform expression or epitope modification (standard IHC practice).
How should I adapt the localisation check for multiplex ATG9A IF?
For an IF localisation check, pair ATG9A with a validated marker for the expected cell population, such as a glandular epithelial marker when examining appendix glandular cells (HPA tissue IHC; standard IF practice). Choose spectrally separated fluorophores and consider a red or far-red ATG9A channel where tissue autofluorescence obscures shorter wavelengths (standard IF practice). Match permeabilisation to the antibody epitope: ATG9A has cytoplasmic and lumenal regions separated by 4 transmembrane segments, so epitope access needs to be assessed experimentally (UniProt Q7Z3C6 topology; standard IF practice). Compare signal with single-stain and no-primary controls before calling overlapping vesicular fluorescence colocalisation (standard IF practice; HPA subcellular).
What causes diffuse or speckled background in ATG9A chromogenic IHC?
Start with a no-primary section and inspect whether colour follows tissue edges, damaged areas or the antibody-treated cells (standard IHC practice). The selected assay used 10% goat serum block, biotinylated goat anti-rabbit secondary antibody, streptavidin–biotin detection and DAB (A03757-3 IHC caption). In a peroxidase-based workflow, include an endogenous peroxidase block and check for background from endogenous biotin when using streptavidin–biotin detection (standard IHC practice). If background persists, titrate primary antibody below the caption's 2 µg/ml starting condition and compare with the same tissue and development time (A03757-3 IHC caption; standard IHC practice). Retain genuine cytoplasmic staining when adjusting thresholds (HPA tissue IHC).
How should ATG9A DAB staining be quantified across specimens? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and viable tissue region before scoring, then apply the same rules to every section (standard IHC practice). Record the percentage of positive cells and staining intensity, or use an H-score from 0–300 when intensity categories can be assigned reproducibly (standard IHC practice). For a spatial analysis, report positive-cell density per mm² of viable tissue and normalise to the relevant cell count or tissue area (standard IHC practice). Keep retrieval, DAB development and image acquisition consistent; a threshold that captures diffuse background will inflate the score (standard IHC practice). Report the compartment scored, because ATG9A is associated with cytoplasmic vesicles and membranes (UniProt Q7Z3C6 subcellular location).
How do I distinguish true ATG9A signal from staining artefact?
Give greatest weight to staining in intact cells with a plausible cytoplasmic or vesicular distribution, since ATG9A mainly localises to the trans-Golgi network and endosomal system (UniProt Q7Z3C6 subcellular location). Check the cell type as well as the compartment: the tissue atlas reports medium staining in appendix glandular cells but no detectable staining in adipose-tissue adipocytes (HPA tissue IHC). Treat that comparison cautiously because the atlas labels its tissue IHC reliability uncertain, pending external verification (HPA tissue IHC). Edge staining, necrotic debris and colour retained in a no-primary or peroxidase-control section warrant investigation before scoring (standard IHC practice). Confirm a surprising pattern with appropriate controls and tissue morphology (standard IHC practice).
Boster reagents
Best ATG9A / Autophagy-related protein 9A IHC Antibodies
Validated anti-ATG9A antibodies include IHC images from human heart, glioma and lung cancer tissue, plus IF images from human heart tissue and A549 cells (catalog image captions).
Real IHC data
Anti-ATG9A Antibody ®
Cat # A03757-3
Real IHC data
Anti-Autophagy-related protein 9A ATG9A Antibody
Cat # A03757
Real IHC data
Anti-ATG9A Rabbit Monoclonal Antibody
Cat # M03757
Real IF data
Anti-ATG9A Antibody ®
Cat # A03757-2
A03757-3 has paraffin-section IHC images from human glioma and mouse brain, while A03757 has human heart IHC and IF images (catalog image captions). M03757 has paraffin-section IHC in human lung cancer and IF in Hepg2 cells; A03757-2 has IF/ICC in A549 cells (catalog image captions).
Which to pick: For tissue IHC, choose A03757-3 when cross-species use matters: human, mouse and rat reactivity is listed, and its own paraffin-section IHC captions show human glioma and mouse brain with EDTA retrieval at pH 8.0; the fixative is unreported (catalog reactivity; A03757-3 IHC captions). For IF/ICC, choose A03757-2, which lists both applications and shows A549 cell IF at 5 μg/mL (catalog applications; A03757-2 IF caption). M03757 is a rabbit monoclonal option for IHC or IF/ICC, with listed human, mouse and rat reactivity; its own IHC caption shows paraffin-embedded human lung cancer, with fixative unreported (catalog: clone FGF-1, applications and reactivity; M03757 IHC caption).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry Q7Z3C6 (ATG9A_HUMAN, Autophagy-related protein 9A).
- Human Protein Atlas. ATG9A tissue IHC expression (reliability: Uncertain).
- Human Protein Atlas. ATG9A subcellular location (ICC-IF): Localized to vesicles..
- Human Protein Atlas. ATG9A antibody validation summary (1 antibodies).
- Region-specific changes in the immunoreactivity of Atg9A in the central nervous system of SOD1(G93A) transgenic mice. Anatomy & cell biology 2014 — PMC4076416.
- Activation of the hypoxia response protects mice from amyloid-β accumulation. Cellular and molecular life sciences : CMLS 2022 — PMC9296391.
- Impact of beta-tricalcium phosphate on preventing tooth extraction-triggered bisphosphonate-related osteonecrosis of the jaw in rats. Scientific reports 2023 — PMC10520003.
- Targeting HIF-P4H-2 in APP/PS1 Alzheimer's mouse model improves glucose metabolism, reduces dystrophic neuritis, and maintains exploratory activity. The Journal of biological chemistry 2025 — PMC12314380.
- PubMed PMID:17974005 — UniProt-cited evidence.
- PubMed PMID:15815621 — UniProt-cited evidence.
- PubMed PMID:15489334 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for ATG9A (Autophagy-related protein 9A). Expected localisation Cytoplasmic tissue staining (HPA tissue IHC). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet A03757-3). Validated IHC antibody: A03757-3 at 2-5μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Adrenal gland (Glandular cells); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human glioma tissue; fixative not specified (datasheet A03757-3); 2. Fixation: Image fixative and duration unreported (datasheet A03757-3); verify before use.; 3. Sectioning: 4–5 µm sections on charged slides (standard); 4. Deparaffinisation: Xylene, graded ethanol series to water (standard); 5. Antigen retrieval: Heat retrieval: EDTA pH 8.0 (datasheet A03757-3); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A03757-3); 8. Primary antibody: Rabbit anti-ATG9A, 2-5μg/ml (datasheet A03757-3); 9. Primary incubation: Overnight at 4 °C (datasheet A03757-3). Watch for: Fixation: Keep fixation consistent across paraffin sections (standard IHC practice; not target-specific); Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image A03757-3); Caveat: Tissue staining awaits external verification (HPA tissue IHC); Isoform / epitope: 3 isoforms; epitope map unknown across cytoplasmic and luminal regions (UniProt); Regulation: Starvation redistributes ATG9A to PAS (UniProt). Evidence: UniProt Q7Z3C6, HPA tissue IHC · Uncertain, HPA ICC-IF · vesicles., Datasheet A03757-3, PMC4076416, PMC9296391. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/ATG9A/immunohistochemistry-ihc-guide.