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ME1 / NADP-dependent malic enzyme · IHC design guide
Design Immunohistochemistry for ME1
Plan ME1 chromogenic IHC in paraffin sections using cytoplasmic staining as the expected pattern (HPA tissue IHC). Adrenal glandular cells provide a strong staining reference (HPA tissue IHC); the catalog antibody M03449 has an IHC dilution of 2–5 μg/mL (datasheet M03449).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
ME1 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 in several tissues (HPA tissue IHC) | |
| Staining pattern | Cytoplasmic staining, strongest in adrenal glandular cells (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet M03449) | |
| Positive control | Adrenal gland+4 more · see all | |
| Negative control | Appendix+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation conditions consistent across sections. (standard IHC practice; not target-specific) | |
| Caveat | Staining has medium agreement with RNA data (HPA tissue IHC) | |
| Regulation | No stimulus-linked regulation specified (UniProt) | |
| Isoform / epitope | Two isoforms; check antibody epitope coverage (UniProt) |
Section 1
Recommended ME1 IHC & IF Protocols
Compare the catalog antibody’s IHC-P protocol (datasheet M03449) with four published ME1 immunohistochemistry protocols (PMC5989842; PMC11850758; PMC6628973; PMC3464285).
| Sample | Paraffin-embedded human liver cancer tissue; fixative not specified (datasheet M03449) |
| Fixation | Image fixative and duration unreported (datasheet M03449); 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 M03449); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet M03449) |
| Primary antibody | Mouse monoclonal (clone 5E5F7) anti-ME1, 2-5 μg/ml (datasheet M03449) |
| Primary incubation | Overnight at 4 °C (datasheet M03449) |
| Detection | HRP-conjugated secondary, DAB chromogen (datasheet M03449) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | ME1-positive staining in glandular cells of adrenal gland (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic expression in several tissues, most abundant in adrenal gland. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated EDTA retrieval at pH 8.0 for the catalog antibody (datasheet M03449); assess staining against an appropriate control.
Section 2
What Is the Expected ME1 Staining Pattern?
ME1 is a cytoplasmic enzyme with no transmembrane segment (UniProt P48163 localization and topology). In paraffin-section IHC, expect cytoplasmic staining in adrenal glandular cells and late spermatids, with weaker staining in several other listed cell types (HPA tissue IHC). HPA rates the tissue profile Enhanced, but describes only medium agreement with RNA data and says external verification is pending (HPA tissue IHC reliability).
| Strong cytoplasmic stain in adrenal glandular cells or elongated/late spermatids. | This matches HPA's High staining in those cell types and UniProt's cytoplasmic localization (HPA tissue IHC; UniProt P48163). Compare cells within the section: HPA levels describe observed cell types, not a uniform intensity across an entire tissue (HPA tissue IHC). |
| Predominantly nuclear or sharply membrane-bound signal replaces cytoplasmic staining. | Treat this as a localization discrepancy and check controls and morphology (UniProt P48163 localization; HPA tissue IHC). HPA reports nucleoplasm and plasma membrane in ICC-IF as uncertain, while its cytosol assignment is supported; the uncertain IF findings do not establish the expected IHC pattern (HPA subcellular ICC-IF). |
| Strong signal appears in a cell type HPA lists as Not detected, such as appendix glandular cells. | Consider cross-reactivity or endogenous chromogenic activity, then verify with assay controls (HPA tissue IHC; general IHC practice). Not detected refers to the named cell type under HPA's conditions; it does not certify that every cell in the organ is negative (HPA tissue IHC). |
| Brown stain spreads across tissue and blank areas without cell boundaries. | Diffuse background prevents a reliable cytoplasmic call (UniProt P48163 localization; general IHC practice). Examine the no-primary control and review blocking, washes, chromogen development and counterstain before assigning ME1 positivity (general IHC practice). |
| No visible signal in adrenal glandular cells on a putative positive section. | This conflicts with HPA's High result for that cell type (HPA tissue IHC). Check tissue identity, section quality, antibody and detection controls, and the catalog IHC-P instructions before calling the sample biologically negative (general IHC practice). |
💡Expected ME1 appearanceCall a positive result when adrenal glandular cells show clear, predominantly cytoplasmic staining at a strong relative intensity; diffuse staining or dominant nuclear or membrane signal warrants control review (HPA tissue IHC; UniProt P48163 localization; HPA subcellular ICC-IF).
| Cell-type baseline in the selected section | Adrenal glandular cells and late spermatids are High, whereas bone-marrow hematopoietic cells, Purkinje cells, cardiomyocytes and listed neuronal cells are Medium (HPA tissue IHC). Select a comparator by cell type and reported level; a negative call for appendix glandular cells or breast adipocytes applies only to those listed cells (HPA tissue IHC). |
| Strength of IHC evidence | HPA006493 is IHC Enhanced, and HPA describes the tissue profile as Enhanced with medium RNA agreement pending external verification (HPA antibodies; HPA tissue IHC). Use that profile as an observed benchmark, while checking the catalog antibody's own IHC-P validation when interpreting a new assay (general IHC practice). |
| IF/ICC Q: Should nuclear or plasma-membrane staining set the IHC expectation? | No. HPA marks those ICC-IF locations uncertain and cytosol supported; ICC validation for HPA006493 is Uncertain (HPA subcellular ICC-IF; HPA antibodies). UniProt places ME1 in the cytoplasm and lists no transmembrane segment (UniProt P48163 localization and topology). Interpret IF/ICC on its own guide page. |
| Situation | Likely cause | Next action |
|---|---|---|
| Adrenal glandular cells have no detectable chromogen. | A failed staining or detection step is possible; HPA records this cell type as High (HPA tissue IHC; general IHC practice). | Confirm the cell type and section quality, run a positive-control section, and check the catalog IHC-P protocol and detection reagents (general IHC practice). |
| Signal is chiefly nuclear or outlines cell membranes. | That distribution conflicts with UniProt's cytoplasmic localization; HPA's corresponding ICC-IF assignments are uncertain (UniProt P48163; HPA subcellular ICC-IF). | Check the no-primary control, chromogen deposits and tissue morphology; require reproducible cytoplasmic signal before scoring IHC positivity (general IHC practice). |
| Appendix glandular cells stain strongly. | HPA lists that specific cell type as Not detected; cross-reactivity or endogenous detection activity is possible, not proven (HPA tissue IHC; general IHC practice). | Compare a no-primary control, verify cell identity and review endogenous enzyme blocking appropriate to the detection chemistry (general IHC practice). |
| Every compartment and tissue area has a brown haze. | Nonspecific background or excessive chromogen development can obscure cell-level localization (general IHC practice). | Inspect the no-primary control; review blocking, antibody conditions, washes and development time against the catalog IHC-P protocol (general IHC practice). |
| A Medium HPA cell type looks weaker than adrenal glandular cells. | This may fit the reported relative staining levels rather than indicate assay failure (HPA tissue IHC). | Score the specified cells and compare them with an appropriate positive-control section under the same detection conditions (HPA tissue IHC; general IHC practice). |
| A whole organ is called ME1-negative because one listed cell type is Not detected. | HPA's negative entries identify particular cells, while UniProt reports expression across tested tissues (HPA tissue IHC; UniProt P48163 tissue specificity). | Record cell identity and compartment in the score; limit the negative conclusion to the examined cell population and assay conditions (general IHC practice). |
Experiment evidence
IHC & IF images showing ME1 staining
M03449 · IHCIHC analysis of ME1 using anti-ME1 antibody (M03449). ME1 was detected in a paraffin-embedded section of human liver cancer tissue. Heat med
M03449 · IHCIHC analysis of ME1 using anti-ME1 antibody (M03449). ME1 was detected in a paraffin-embedded section of human spleen tissue. Heat mediated
A03449-3 · IHCIHC analysis of ME1 using anti-ME1 antibody (A03449-3). ME1 was detected in a paraffin-embedded section of human stomach cancer tissue. Heat
A03449-3 · IFIF analysis of ME1 using anti-ME1 antibody (A03449-3) and anti-Tubulin Alpha antibody (M03989-3). ME1 was detected in immunocytochemical sec
A03449 · IHCImmunohistochemistry of ME1 in mouse liver tissue with ME1 antibody at 5 μg/mL.
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000065833-ME1/tissue/cerebral+cortex#imid_2010288
HPA · Adrenal glandHuman Protein Atlas IHC, Adrenal gland. Source: https://www.proteinatlas.org/ENSG00000065833-ME1/tissue/adrenal+gland#imid_2010264
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000065833-ME1/tissue/colon#imid_2010214
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000065833-ME1/tissue/liver#imid_2010223
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA006493; green = ME1, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA006493; green = ME1, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for ME1 IHC & IF
🧪Run adrenal gland first: its glandular cells should stain (HPA: High in adrenal gland glandular cells). Use appendix glandular cells as the negative tissue (HPA: Not detected in appendix glandular cells); on the adrenal slide, assess cells without specific staining as internal background without assigning a named cell type as ME1-negative.
Positive control tissue: Adrenal gland (Glandular cells, HPA High)
Negative control tissue: Appendix (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show ME1 in A-431, CACO-2, U2OS, with annotated localisation: Nucleoplasm (uncertain), Plasma membrane (uncertain) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control, an isotype-matched mouse IgG control, and a biological negative such as ME1 knockout material (caption: mouse anti-ME1 primary). Quench endogenous peroxidase and check for pigment that could resemble DAB signal in adrenal tissue (caption: peroxidase detection with DAB).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected M03449 tissue-IHC caption does not state the fixative (caption: fixative unreported). The caption uses heat-mediated retrieval in EDTA at pH 8.0, but does not establish that retrieval is required (caption: EDTA retrieval). No supplied comparison establishes that frozen sections or IF are easier; for IF interpretation, note the supported cytosolic signal alongside uncertain nucleoplasmic and plasma-membrane signals (HPA: subcellular ICC-IF).
HPA tissue IHC evidence for ME1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — Medium consistency between antibody staining and RNA expression data. 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 | High | Protein (IHC) | HPA → |
| Testis | Elongated or late spermatids | High | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic 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 |
|---|---|---|---|---|
| Appendix | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Breast | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Bronchus | Respiratory epithelial cells | Not detected | Protein (IHC) | HPA → |
| Colon | Endothelial cells | Not detected | Protein (IHC) | HPA → |
| Endometrium | Cells in endometrial stroma | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced ME1 IHC Tips
Troubleshoot ME1 staining in paraffin sections by checking retrieval, background and cellular localisation before comparing signal intensity across samples.
What should I change when ME1 staining is weak after retrieval?
Start with heat-mediated antigen retrieval in EDTA at pH 8.0 for paraffin sections (datasheet M03449). The selected ME1 tissue image used this retrieval before incubation with 2 μg/ml antibody overnight at 4°C, so keep those conditions consistent while assessing retrieval (datasheet M03449). If staining remains weak, adjust heating time in small increments and compare sections from the same block, checking that tissue morphology remains intact (standard IHC practice). Use an antibody-omission control and a known positive section to distinguish poor antigen exposure from weak detection (standard IHC practice; HPA: high in adrenal gland glandular cells).
Could fixation explain weak or uneven ME1 staining?
ME1-specific sensitivity to fixation is unknown: the selected paraffin-section caption does not state a fixative (datasheet M03449). Record the fixative, fixation duration and section age for each case, then compare sections processed under matched conditions before changing the antibody concentration (standard IHC practice). Examine whether staining varies with tissue thickness or is strongest at cut edges, because those patterns warrant a processing check rather than an immediate biological interpretation (standard IHC practice). Keep heat-mediated EDTA retrieval at pH 8.0 and the documented 2 μg/ml primary incubation constant during that comparison (datasheet M03449).
How should I evaluate nuclear or membrane ME1 staining in IHC?
Expect predominantly cytoplasmic tissue staining when evaluating ME1 in paraffin sections (UniProt P48163: cytoplasm; HPA tissue IHC: cytoplasmic expression in several tissues). HPA subcellular imaging also reports nucleoplasm and plasma membrane as uncertain locations, with cytosol supported, so record those patterns separately rather than pooling all positive signal (HPA subcellular). ME1 has no annotated transmembrane segment or signal peptide, making a crisp membrane-only IHC pattern a reason to check specificity and compartment assignment (UniProt P48163 topology and processing). Compare the pattern with a positive control and an antibody-omission section at the same counterstain intensity (standard IHC practice; HPA: high in adrenal gland glandular cells).
Can isoforms or epitope accessibility cause discordant ME1 staining?
ME1 has 2 annotated isoforms, but the supplied M03449 caption does not identify its epitope or establish isoform-specific staining (UniProt P48163 isoforms; datasheet M03449). Therefore, interpret a negative paraffin section as absence of detectable staining under the tested conditions, not proof that both isoforms are absent (standard IHC interpretation; UniProt P48163 isoforms). The record lists N-acetylmethionine at residue 1 and phosphoserine at 336; neither establishes an effect on this antibody without epitope mapping (UniProt P48163 modified residues; datasheet M03449). If two antibodies disagree, compare their documented immunogens and staining compartments using matched sections and controls (standard IHC practice).
How can IF help investigate an ambiguous IHC cell pattern?
Use IF/ICC as a separate validation experiment, because the selected M03449 evidence documents chromogenic paraffin-section IHC rather than an IF protocol (datasheet M03449). Multiplex ME1 with a marker for the cell population being assessed; adrenal gland glandular cells provide one evidence-based positive population to examine (HPA: high in adrenal gland glandular cells; standard IF practice). Choose fluorophores after checking tissue autofluorescence and include single-stain controls so bleed-through does not mimic colocalisation (standard IF practice). For a cytosolic epitope, include permeabilisation; for a proposed membrane-facing epitope, first establish which side it occupies, since ME1 has no annotated transmembrane segment (HPA subcellular: cytosol supported; UniProt P48163 topology; standard IF practice).
What causes diffuse brown signal in ME1 paraffin-section IHC?
First compare the stained section with an antibody-omission control to separate primary-antibody staining from detection or tissue background (standard IHC practice). The selected image used 10% goat serum blocking, a peroxidase-conjugated secondary and DAB development; these document that example, not a universal ME1-specific background remedy (datasheet M03449). Include a peroxidase-blocking step and inspect pigment or precipitate before increasing stringency, since each can complicate chromogenic interpretation (standard IHC practice). If diffuse signal persists, titrate around the documented 2 μg/ml primary concentration while keeping retrieval at EDTA pH 8.0 and section processing matched (datasheet M03449; standard IHC practice).
How should I score ME1 staining across paraffin sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and cytoplasmic compartment before scoring, because ME1 tissue IHC is described as cytoplasmic and its abundance differs among sampled cells (HPA tissue IHC). For intensity scoring, report an H-score from 0–300 with the percentage of cells at each intensity; alternatively report percentage positive cells using a fixed threshold (standard IHC scoring practice). Normalise counts to evaluable cells, or positive-cell density to analysed tissue area in mm², and exclude folds, necrosis and section edges by a prespecified rule (standard IHC scoring practice). Apply identical retrieval, imaging and scoring thresholds across groups, then report the control tissue and antibody-omission result alongside the scores (standard IHC practice; datasheet M03449: EDTA pH 8.0 retrieval).
When is a positive ME1 stain convincing rather than artefactual?
A convincing result shows interpretable cytoplasmic staining in intact cells and agrees with the study's positive and antibody-omission controls (UniProt P48163: cytoplasm; HPA tissue IHC: cytoplasmic expression; standard IHC practice). HPA reports high staining in adrenal gland glandular cells and elongated or late spermatids, while its tissue profile has only medium consistency with RNA data and awaits external verification (HPA tissue IHC). Question isolated nuclear or membrane-only staining, unexpected cell attribution, edge accentuation and necrotic deposits before treating them as ME1 biology (HPA subcellular: nuclear and membrane locations uncertain; standard IHC practice). Check endogenous peroxidase and DAB background with appropriate detection controls, then corroborate disputed localisation independently (standard IHC practice).
Boster reagents
Best ME1 / NADP-dependent malic enzyme IHC Antibodies
Anti-ME1 IHC images cover human liver cancer, spleen, and stomach cancer, rat testis, and mouse liver (catalog IHC captions); IF images cover A549 cells and human gastric cancer sections (A03449-3 IF captions).
Real IHC data
Anti-ME1 Antibody ® (monoclonal, 5E5F7)
Cat # M03449
Real IHC data
Anti-ME1 Antibody ®
Cat # A03449-3
Real IHC data
Anti-NADP-dependent malic enzyme ME1 Antibody
Cat # A03449
M03449 shows paraffin-section IHC in human liver cancer, human spleen, and rat testis (M03449 IHC captions); A03449-3 shows paraffin-section IHC in human stomach cancer (A03449-3 IHC caption). A03449 shows IHC in mouse liver (A03449 IHC caption), while A03449-3 also shows IF in A549 cells and paraffin-embedded human gastric cancer tissue (A03449-3 IF captions).
Which to pick: For human or rat paraffin-section IHC, M03449 is a mouse monoclonal (clone 5E5F7; M03449 catalog) with images from both species (M03449 IHC captions); A03449-3 is a rabbit option with a human stomach cancer paraffin-section image (A03449-3 IHC caption). For IF/ICC, choose A03449-3, which lists both applications and has IF images from A549 cells and human gastric cancer sections (A03449-3 applications and IF captions). For cross-species planning, all three list human, mouse, and rat reactivity (catalog reactivity), while A03449 provides a mouse liver IHC image at 5 μg/mL (A03449 IHC caption); fixatives are unreported in the IHC captions (catalog IHC captions).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P48163 (MAOX_HUMAN, NADP-dependent malic enzyme).
- Human Protein Atlas. ME1 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. ME1 subcellular location (ICC-IF): Mainly localized to the nucleoplasm and plasma membrane. In addition localized to the cytosol..
- Human Protein Atlas. ME1 antibody validation summary (1 antibodies).
- Expression of cytosolic malic enzyme (ME1) is associated with disease progression in human oral squamous cell carcinoma. Cancer science 2018 — PMC5989842.
- Identification and Validation of Biomarkers in Metabolic Dysfunction-Associated Steatohepatitis Using Machine Learning and Bioinformatics. Molecular genetics & genomic medicine 2025 — PMC11850758.
- Malic enzyme 1 (ME1) is a potential oncogene in gastric cancer cells and is associated with poor survival of gastric cancer patients. OncoTargets and therapy 2019 — PMC6628973.
- Cytosolic malic enzyme 1 (ME1) mediates high fat diet-induced adiposity, endocrine profile, and gastrointestinal tract proliferation-associated biomarkers in male mice. PloS one 2012 — PMC3464285.
- PubMed PMID:8187880 — UniProt-cited evidence.
- PubMed PMID:7622060 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for ME1 (NADP-dependent malic enzyme). Expected localisation Cytoplasmic staining in several tissues (HPA tissue IHC). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet M03449). Validated IHC antibody: M03449 at 2-5 μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Adrenal gland (Glandular cells); negative Appendix. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human liver cancer tissue; fixative not specified (datasheet M03449); 2. Fixation: Image fixative and duration unreported (datasheet M03449); 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 M03449); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet M03449); 8. Primary antibody: Mouse monoclonal (clone 5E5F7) anti-ME1, 2-5 μg/ml (datasheet M03449); 9. Primary incubation: Overnight at 4 °C (datasheet M03449). Watch for: Fixation: Keep fixation conditions consistent across sections. (standard IHC practice; not target-specific); Caveat: Staining has medium agreement with RNA data (HPA tissue IHC); Isoform / epitope: Two isoforms; check antibody epitope coverage (UniProt); Regulation: No stimulus-linked regulation specified (UniProt). Evidence: UniProt P48163, HPA tissue IHC · Enhanced, HPA ICC-IF · Mainly localized to the nucleoplasm and plasma membrane. In addition…, Datasheet M03449, PMC5989842, PMC11850758. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/ME1/immunohistochemistry-ihc-guide.