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ME2 / NAD-dependent malic enzyme, mitochondrial · IHC design guide
Design Immunohistochemistry for ME2
Plan ME2 chromogenic IHC around granular cytoplasmic tissue staining, with mitochondrial matrix localization as the molecular expectation (HPA tissue IHC; UniProt). Colon glandular cells provide a high-staining reference (HPA tissue IHC); start catalog antibody A01380-1 at 0.5–1 μg/mL (datasheet A01380-1).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
ME2 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 | Granular cytoplasm; mitochondrial matrix expected (HPA tissue IHC; UniProt) | |
| Staining pattern | Variable granular cytoplasmic staining across cell types (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet A01380-1) | |
| Positive control | Adrenal gland+4 more · see all | |
| Negative control | None in HPA (detected in all 45 tissues); use no-primary + isotype controls |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation consistent across paraffin sections. (standard IHC practice; not target-specific) | |
| Caveat | Low staining in myocytes may resemble absence (HPA tissue IHC) | |
| Regulation | Cell-type-dependent abundance (HPA tissue IHC) | |
| Isoform / epitope | Two isoforms; epitope coverage cannot be mapped from this record (UniProt) |
Section 1
Recommended ME2 IHC & IF Protocols
The catalog antibody's IHC-P protocol (datasheet: A01380-1) is accompanied by three published ME2 IHC protocols (PMC11555414; PMC7085265; PMC8495273).
| Sample | Paraffin-embedded human ovarian cancer tissue; fixative not specified (datasheet A01380-1) |
| Fixation | Image fixative and duration unreported (datasheet A01380-1); 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 A01380-1); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A01380-1) |
| Primary antibody | Rabbit anti-ME2, 0.5-1μg/ml (datasheet A01380-1) |
| Primary incubation | Overnight at 4 °C (datasheet A01380-1) |
| Detection | Streptavidin-biotin complex (SABC), DAB chromogen (datasheet A01380-1) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | ME2-positive staining in glandular cells of adrenal gland (HPA tissue IHC: High). HPA tissue profile: Granular cytoplasmic expression at variable levels in all cell types. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated EDTA pH 8.0 retrieval for the catalog antibody (datasheet: A01380-1). The OSCC study used citrate pH 6.0 (PMC7085265).
Section 2
What Is the Expected ME2 Staining Pattern?
ME2 is a soluble mitochondrial matrix enzyme with no transmembrane segment (UniProt P23368 topology). In paraffin-section IHC, expect granular cytoplasmic staining at variable levels across cell types (HPA tissue IHC: Enhanced). HPA reports high staining in several epithelial, glandular and neuronal populations, including colon glandular cells and cerebellar Purkinje cells (HPA tissue IHC). Use those observed patterns to judge a slide; morphology alone cannot prove mitochondrial localisation.
| Granular cytoplasmic staining in colon glandular cells, with little nuclear emphasis. | This fits the reported high glandular-cell staining (HPA: colon) and mitochondrial matrix localisation (UniProt P23368). Judge intensity against nearby tissue and controls; granules on a chromogenic slide suggest the expected compartment but do not establish mitochondrial identity by themselves. |
| Predominantly nuclear, crisp plasma-membrane, or extracellular staining. | These compartments conflict with matrix localisation and the reported granular cytoplasmic IHC profile (UniProt P23368; HPA tissue IHC). Consider nonspecific binding or staining artefact, especially if the expected cytoplasmic pattern is absent; review morphology and controls before calling the signal ME2. |
| Uniformly intense staining in a population HPA reports as low, such as adipocytes. | HPA reports low adipocyte staining, while expression varies among cell types (HPA: adipose tissue; HPA tissue IHC profile). A striking reversal warrants checking cross-reactivity or endogenous detection activity. Low is not absent: HPA supplies no negative tissue here, so staining alone cannot establish a false positive. |
| Diffuse color across stroma, empty spaces, and cell types without discernible cytoplasmic granules. | This obscures the expected granular cytoplasmic pattern (HPA tissue IHC). Uneven reagent coverage, excess antibody, or background from the detection system are general IHC possibilities (general IHC practice). Compare a no-primary control and repeat with controlled reagent coverage before scoring cellular expression. |
| No staining in a section containing bronchial respiratory epithelium expected to stain strongly. | HPA reports high ME2 staining in these cells (HPA: bronchus). If tissue preservation and morphology are adequate, a blank result calls for checking the assay controls, antibody dilution, retrieval conditions, and detection reagents (general IHC practice). One negative slide does not establish absent ME2. |
💡Expected ME2 appearanceCall a convincing positive result when intact cells show granular cytoplasmic staining, especially high signal in HPA-listed positive populations; isolated nuclear, membrane, or diffuse extracellular color is suspicious (HPA tissue IHC; UniProt P23368).
| Subcellular reference | ME2 resides in the mitochondrial matrix and has no transmembrane segment (UniProt P23368). HPA describes granular cytoplasmic IHC staining; a chromogenic pattern remains a morphological inference, not direct organelle confirmation (HPA tissue IHC). |
| Choice of comparison tissue | Colon glandular cells and bronchial respiratory epithelial cells are high examples; salivary glandular cells and adipocytes are low examples (HPA tissue IHC). HPA lists no negative population, so low-expression tissue is a graded comparator, not a zero-signal control. |
| Antibody evidence | HPA rates tissue IHC reliability Enhanced and lists HPA008247 and HPA008880 as Enhanced for IHC (HPA tissue IHC; HPA antibodies). This supports the reported pattern, but does not validate an unspecified catalog antibody or supply its working dilution. |
| Molecular processing and variants | UniProt records two isoforms and a mature chain spanning residues 19–584 (UniProt P23368). The payload gives no antibody epitope map, so these facts cannot predict which isoform is detected or explain a weak section. |
| Chromogenic detection background | Endogenous enzyme activity can contribute color in enzyme-based IHC (general IHC practice). Appropriate blocking and a no-primary control help distinguish detection-system background from the HPA-reported granular cellular pattern (HPA tissue IHC; general IHC practice). |
| Situation | Likely cause | Next action |
|---|---|---|
| Known-positive tissue is blank. | The assay may have lost sensitivity; bronchial respiratory epithelium is reported high (HPA: bronchus). | Check positive-control staining and detection reagents, then review retrieval and titrate the IHC-validated antibody using its instructions (general IHC practice). |
| Color appears predominantly nuclear or along cell borders. | That distribution disagrees with ME2 matrix localisation and HPA's granular cytoplasmic profile (UniProt P23368; HPA tissue IHC). | Check tissue morphology, no-primary control, and antibody concentration before interpreting the signal as specific (general IHC practice). |
| High staining appears in a low-reference population. | Relative intensity differs from the HPA example; adipocytes are reported low, though not negative (HPA: adipose tissue). | Compare with an HPA high population on a matched run and examine controls for cross-reactivity or endogenous activity (HPA tissue IHC; general IHC practice). |
| Diffuse background hides cellular granules. | Excess antibody or detection background can obscure compartment assessment (general IHC practice). | Inspect the no-primary control, verify even reagent coverage, and titrate antibody or detection conditions before rescoring (general IHC practice). |
| Staining is weak but visible in many cell types. | ME2 staining varies across cell types, and HPA reports granular expression broadly (HPA tissue IHC). | Keep weak cellular signal distinct from diffuse background; score against a high-reference tissue and matched controls rather than forcing a positive/negative split (HPA tissue IHC; general IHC practice). |
| What should IF/ICC show? | HPA reports mainly mitochondrial localisation in ICC-IF, consistent with the matrix annotation (HPA subcellular; UniProt P23368). | Assess whether punctate cytoplasmic signal overlaps a mitochondrial marker and check IF controls; use the separate IF/ICC guide for method details (general IF practice). |
Experiment evidence
IHC & IF images showing ME2 staining
A01380-1 · IHCIHC analysis of ME2 using anti-ME2 antibody (A01380-1). ME2 was detected in paraffin-embedded section of human ovarian cancer tissue. Heat m
A01380-1 · IHCIHC analysis of ME2 using anti-ME2 antibody (A01380-1). ME2 was detected in paraffin-embedded section of human rectal cancer tissue. Heat me
A01380-1 · IFIF analysis of ME2 using anti-ME2 antibody (A01380-1). ME2 was detected in immunocytochemical section of Hela cells. Enzyme antigen retrieva
M01380 · IHCM01380 staining ME2 in human kidney tissue sections by Immunohistochemistry (IHC-P -paraformaldehyde-fixed, paraffin-embedded sections). Tis
A01380 · IHCImmunohistochemistry of ME2 in human spleen tissue with ME2 antibody at 5 μg/mL.
A01380 · IFImmunofluorescence of ME2 in human spleen tissue with ME2 antibody at 20 μg/mL.
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000082212-ME2/tissue/cerebral+cortex#imid_2585516
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000082212-ME2/tissue/colon#imid_2585450
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000082212-ME2/tissue/liver#imid_2585435
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000082212-ME2/tissue/kidney#imid_2585436
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA008247; green = ME2, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA008247; green = ME2, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for ME2 IHC & IF
🧪Run adrenal gland first and expect staining in its glandular cells (HPA: High in adrenal gland glandular cells). HPA detects ME2 in all 45 scored tissues, so there is no validated negative tissue; use no-primary and isotype controls, and treat unstained cells within the positive section as a background reference rather than a proven ME2-negative population (HPA: no negative tissue rows; detected in all 45 scored tissues).
Positive control tissue: Adrenal gland (Glandular cells, HPA High)
Negative control tissue: None in HPA: ME2 is detected in all 45 scored tissues. Use a no-primary (secondary-only) and an isotype control instead.
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show ME2 in A-431, U-251MG, U2OS, with annotated localisation: Mitochondria (supported) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control and a rabbit IgG isotype control matched to the catalog antibody; its clonality is unreported (A01380-1 caption: rabbit anti-ME2 antibody). Confirm specificity with ME2 knockout tissue or cells showing loss of staining, and control endogenous peroxidase and biotin in adrenal sections when using the caption’s biotin-based DAB detection (A01380-1 caption: biotinylated secondary, SABC and DAB).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected paraffin-section caption does not state the fixative (A01380-1 caption: fixative not stated). The caption uses heat retrieval in EDTA at pH 8.0, but does not establish that retrieval is required or that frozen sections or IF are easier (A01380-1 caption: EDTA heat retrieval; HPA: mitochondrial ICC-IF images). Endogenous biotin is a potential background source with the caption’s SABC method in adrenal tissue, so assess it with the detection controls (A01380-1 caption: SABC detection; HPA: adrenal gland positive tissue).
HPA tissue IHC evidence for ME2
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — High 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 | High | Protein (IHC) | HPA → |
| Appendix | Glandular cells | High | Protein (IHC) | HPA → |
| Bronchus | Respiratory epithelial cells | High | Protein (IHC) | HPA → |
| Cerebellum | Purkinje cells | High | Protein (IHC) | HPA → |
| Cerebral cortex | Neuronal cells | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| None in HPA: ME2 is detected in all 45 scored tissues. Use a no-primary (secondary-only) and an isotype control instead. | ||||
Section 3
Advanced ME2 IHC Tips
Use the catalog antibody’s paraffin-section IHC conditions as a starting point, then assess staining against ME2’s expected mitochondrial pattern.
Which retrieval conditions should I start with for ME2 paraffin-section IHC?
Start with heat-mediated retrieval in EDTA pH 8.0 for paraffin sections (datasheet A01380-1). The selected tissue-IHC example used this retrieval before an overnight incubation at 4°C with 1 μg/ml catalog antibody (datasheet A01380-1). Keep section thickness, heating time and cooling time consistent across a comparison series, and check that tissue remains attached after heating (standard IHC practice). If staining is weak, adjust retrieval duration in a small series before considering another buffer, while monitoring tissue damage and background (standard IHC practice). Compare the resulting pattern with granular cytoplasmic staining, rather than judging intensity alone (HPA tissue IHC).
How should I troubleshoot weak staining when fixation history is uncertain?
ME2-specific sensitivity to fixation is unknown from the supplied evidence: the selected paraffin-section caption does not state a fixative (datasheet A01380-1). Record the specimen’s actual fixative and fixation history, then compare sections processed together with the same EDTA pH 8.0 retrieval and antibody concentration (datasheet A01380-1; standard IHC practice). Include a tissue region with interpretable morphology so that loss of staining can be assessed alongside preservation of cellular detail (standard IHC practice). If fixation varies between specimens, avoid treating an intensity difference as a biological ME2 difference until a matched processing comparison supports it (standard IHC practice).
What staining pattern is consistent with ME2 in chromogenic IHC?
Look for cytoplasmic granularity consistent with a mitochondrial protein, while recognizing that DAB staining does not resolve individual mitochondrial compartments (UniProt P23368 localisation; HPA tissue IHC; standard IHC practice). ME2 is assigned to the mitochondrial matrix and has no annotated transmembrane segment, so a sharp plasma-membrane outline is unexpected (UniProt P23368 localisation and topology). Compare staining within identifiable cells and inspect the matching counterstained morphology before assigning a compartment (standard IHC practice). The HPA reports variable granular cytoplasmic expression across cell types, so differences in intensity alone do not establish a localisation change (HPA tissue IHC).
Could isoforms or processing explain a change in ME2 staining?
ME2 has 2 annotated isoforms, and its annotated mature chain spans residues 19–584 (UniProt P23368 isoforms and processing). The supplied antibody caption does not identify its epitope, so these annotations cannot establish whether the catalog antibody detects both isoforms equally (datasheet A01380-1; UniProt P23368 isoforms). Several lysine acetylation sites are annotated, but their effect on this antibody’s binding is unknown (UniProt P23368 modified residues; datasheet A01380-1). For discordant specimens, compare staining under identical retrieval and detection conditions, then seek independent epitope or antibody-validation information before attributing the difference to an isoform or modification (standard IHC practice).
How can I examine ME2 by IF alongside cell-type markers?
Treat IF as a separate assay: the selected antibody example establishes paraffin-section chromogenic IHC conditions, not IF performance (datasheet A01380-1). Pair ME2 with a marker identifying the cell population being evaluated, and choose spectrally distinct fluorophores after checking unstained tissue for autofluorescence (standard IF practice). Because ME2 is assigned to the mitochondrial matrix, test permeabilisation that permits antibody access across cellular and mitochondrial membranes, using controls to assess whether morphology is preserved (UniProt P23368 localisation; standard IF practice). Evaluate a granular mitochondrial pattern with single-label controls before interpreting overlap; apparent colocalisation can arise from channel bleed-through or autofluorescence (HPA subcellular; standard IF practice).
How do I separate ME2 signal from chromogenic background?
The selected IHC example used 10% goat serum blocking, a biotinylated secondary antibody and DAB development (datasheet A01380-1). For diffuse staining, review primary-antibody concentration, washing, peroxidase blocking and DAB development time together, while keeping the positive tissue control in the run (datasheet A01380-1; standard IHC practice). Include a primary-omission control to identify signal from the detection system, and inspect tissue edges or damaged regions separately from intact cells (standard IHC practice). Because the example uses biotin-based detection, a matched detection-only control can help assess tissue-associated signal unrelated to primary-antibody binding (datasheet A01380-1; standard IHC practice).
What is a defensible way to quantify ME2 IHC across specimens? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and viable analysis area before scoring, and apply the same threshold and imaging settings across specimens (standard IHC practice). Report the percentage of positive cells together with an intensity score, or calculate an H-score from intensity categories 0–3 to give a range of 0–300 (standard IHC practice). If counting stained cells, report density per mm² of viable tissue and exclude folds, edges and necrosis by a prespecified rule (standard IHC practice). Normalize comparisons to the same cell type or tissue compartment and include a reference section across staining runs, since ME2 expression varies among cell types (HPA tissue IHC; standard IHC practice).
Which findings should make me question an apparent ME2-positive result?
A convincing result shows granular cytoplasmic staining in intact cells, consistent with ME2’s mitochondrial matrix assignment and the reported tissue-IHC pattern (UniProt P23368 localisation; HPA tissue IHC). A strong nuclear or crisp plasma-membrane pattern warrants review because it does not match that expected localisation (UniProt P23368 localisation and topology). Check whether staining follows tissue edges, necrotic areas or damaged cells, and whether it persists without primary antibody; these findings can indicate preparation or detection artefacts (standard IHC practice). Review peroxidase-block and detection controls before assigning DAB signal to ME2, then compare the questioned cells with the appropriate counterstained morphology (standard IHC practice).
Boster reagents
Best ME2 / NAD-dependent malic enzyme, mitochondrial IHC Antibodies
The catalog shows ME2 IHC in human spleen, kidney and ovarian cancer tissue, and rat intestine; IF images show HeLa cells and human intestinal cancer tissue (catalog image captions).
Real IHC data
Anti-ME2 Antibody ®
Cat # A01380-1
Real IHC data
Anti-ME2 Antibody (C-term)
Cat # M01380
Real IHC data
Anti-ME2 Antibody
Cat # A01380
A01380 has human spleen IHC and IF images; A01380-1 has human ovarian cancer and rat intestine IHC images, plus HeLa cell and human intestinal cancer IF images (catalog image captions). M01380 has a human kidney IHC-P image and lists human and mouse reactivity (catalog image caption; catalog applications and reactivity).
Which to pick: For tissue IHC, choose A01380 for human spleen at 5 μg/mL (A01380 image caption), A01380-1 for human or rat paraffin sections at 0.5–1 μg/mL (A01380-1 dilution listing and IHC image captions), or mouse monoclonal M01380 for human kidney at 1:25 (M01380 image caption; catalog clone and host). For IF/ICC, A01380-1 lists both applications and human IF images; its catalog reactivity also includes monkey and mouse, although its IHC captions show human and rat tissue (A01380-1 applications, reactivity and image captions). Fixation is unreported in the A01380 and A01380-1 IHC captions; the M01380 kidney caption reports fixation (catalog image captions). The selected A01380-1 tissue-IHC caption documents paraffin sections, but does not specify the fixative (selected-SKU IHC image A01380-1).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P23368 (MAOM_HUMAN, NAD-dependent malic enzyme, mitochondrial).
- Human Protein Atlas. ME2 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. ME2 subcellular location (ICC-IF): Mainly localized to the mitochondria..
- Human Protein Atlas. ME2 antibody validation summary (2 antibodies).
- PRMT1-mediated methylation of ME2 promotes hepatocellular carcinoma growth by inhibiting ubiquitination. Cell death & disease 2024 — PMC11555414.
- Overexpression of Malic Enzyme 2 Indicates Pathological and Clinical Significance in Oral Squamous Cell Carcinoma. International journal of medical sciences 2020 — PMC7085265.
- Malic enzyme 2 promotes the progression of hepatocellular carcinoma via increasing triglyceride production. Cancer medicine 2021 — PMC8495273.
- ME2 Promotes Proneural-Mesenchymal Transition and Lipogenesis in Glioblastoma. Frontiers in oncology 2021 — PMC8351415.
- PubMed PMID:1993674 — UniProt-cited evidence.
- PubMed PMID:11401430 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for ME2 (NAD-dependent malic enzyme, mitochondrial). Expected localisation Granular cytoplasm; mitochondrial matrix expected (HPA tissue IHC; UniProt). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet A01380-1). Validated IHC antibody: A01380-1 at 0.5-1μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Adrenal gland (Glandular cells); negative None in HPA (detected in all 45 tissues); use no-primary + isotype controls. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human ovarian cancer tissue; fixative not specified (datasheet A01380-1); 2. Fixation: Image fixative and duration unreported (datasheet A01380-1); 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 retrieval: EDTA pH 8.0 (datasheet A01380-1); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A01380-1); 8. Primary antibody: Rabbit anti-ME2, 0.5-1μg/ml (datasheet A01380-1); 9. Primary incubation: Overnight at 4 °C (datasheet A01380-1). Watch for: Fixation: Keep fixation consistent across paraffin sections. (standard IHC practice; not target-specific); Caveat: Low staining in myocytes may resemble absence (HPA tissue IHC); Isoform / epitope: Two isoforms; epitope coverage cannot be mapped from this record (UniProt); Regulation: Cell-type-dependent abundance (HPA tissue IHC). Evidence: UniProt P23368, HPA tissue IHC · Enhanced, HPA ICC-IF · Mainly localized to the mitochondria., Datasheet A01380-1, PMC11555414, PMC7085265. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/ME2/immunohistochemistry-ihc-guide.