This website uses cookies to ensure you get the best experience on our website.
- Table of Contents
TMEM18 / Transmembrane protein 18 · IHC design guide
Design Immunohistochemistry for TMEM18
Plan chromogenic IHC-P for TMEM18 using the IHC-validated antibody (datasheet: IHC-P). Compare observed cytoplasmic tissue staining (HPA tissue IHC) with the nuclear membrane location annotated for the protein (UniProt), and account for medium consistency between staining and RNA data (HPA tissue IHC).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
TMEM18 Immunohistochemistry Experimental Design Guide
Expected localisation, validated protocols, controls and antibodies — the at-a-glance facts below, then the full design guide.
Must know before staining
| Expected localisation | Cytoplasmic staining (HPA tissue IHC); nuclear membrane expected (UniProt) | |
| Staining pattern | Cytoplasmic staining, including glandular cells (HPA tissue IHC) | |
| Antigen retrieval | Tris-EDTA pH 9.0 HIER, 95–98 °C, 20 min (rule: nuclear antigen) | |
| Positive control | Epididymis+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 sections (standard IHC practice; not target-specific) | |
| Caveat | Medium staining–RNA consistency; verify signal (HPA tissue IHC) | |
| Regulation | No staining-linked regulation annotated (UniProt) | |
| Isoform / epitope | 2 isoforms; epitope coverage is unknown (UniProt) |
Section 1
Recommended TMEM18 IHC & IF Protocols
Compare the catalog antibody’s IHC-P protocol (datasheet) with the published FFPE prostate carcinoma tissue microarray protocol (PMC12203752).
| Sample | Tissue sections; selected-image fixative not specified (standard IHC workflow) |
| Fixation | Image fixative and duration unreported (datasheet A05347); 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-TMEM18, 2.5 μg/mL (datasheet A05347) |
| 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 | TMEM18-positive staining in glandular cells of epididymis (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic expression in most tissues. No signal in the no-primary control. |
💡Decision noteStart with Tris-EDTA pH 9.0 retrieval at 95–98 °C for 20 min (page retrieval rule); the published protocol does not specify retrieval (PMC12203752).
Section 2
What Is the Expected TMEM18 Staining Pattern?
For paraffin-section IHC, expect predominantly cytoplasmic staining in many tissues, with high staining reported in selected glandular and trophoblastic cells (HPA tissue IHC). UniProt also places TMEM18 at the nuclear membrane and describes 3 transmembrane segments (UniProt Q96B42 topology). Treat the tissue pattern as a guide: HPA rates its IHC reliability Approved, with medium agreement between staining and RNA data and external verification pending (HPA tissue IHC).
| Clear cytoplasmic stain in pancreatic exocrine glandular cells, with little diffuse background. | This fits a reported high-staining cell population and the predominant tissue-IHC compartment (HPA tissue IHC). Compare cell-associated signal with a no-primary control before scoring; chromogen across empty spaces does not establish TMEM18 staining (general IHC practice). |
| A nuclear rim, isolated nuclear stain, or another compartment dominates while cytoplasmic staining is weak. | A nuclear rim is plausible from the annotated nuclear-membrane location, but it is not the predominant reported tissue-IHC pattern (UniProt Q96B42 subcellular location; HPA tissue IHC). Isolated nuclear stain should prompt a control and localization review before interpretation (general IHC practice). |
| Strong stain appears mainly in adipocytes, skeletal myocytes, or esophageal squamous cells. | These cell populations are listed as Not detected, so the result conflicts with the HPA reference pattern (HPA tissue IHC). Check cell identification and controls; cross-reactivity or endogenous detection activity are possible explanations, not established causes (general IHC practice). |
| Uniform haze covers multiple cell types, stroma, or tissue-free regions. | The expected reference is cell-associated cytoplasmic staining, not an indiscriminate field-wide signal (HPA tissue IHC; general IHC practice). Review the no-primary control and detection background before assigning positive cells (general IHC practice). |
| No convincing signal appears in an otherwise interpretable pancreatic exocrine compartment. | Pancreatic exocrine glandular cells are reported High, making them a useful comparator, though one negative section cannot prove antibody failure (HPA tissue IHC). Check tissue identity, controls, reagent performance, and staining conditions before calling the sample negative (general IHC practice). |
💡Expected TMEM18 appearanceCall a positive IHC result when discrete, predominantly cytoplasmic staining reaches a clear high level in HPA-reported high populations such as pancreatic exocrine glandular cells; widespread cell-independent haze or dominant stain in HPA-listed Not detected cells is suspect (HPA tissue IHC; general IHC practice).
| Tissue and cell choice | HPA reports High staining in epididymal, salivary, seminal-vesicle, and stomach glandular cells; pancreatic exocrine glandular cells; and placental trophoblastic cells (HPA tissue IHC). Appendix and breast glandular cells are Medium. Use the named cell population, not the entire organ, when judging a control (HPA tissue IHC; general IHC practice). |
| Reference reliability | The tissue-IHC profile is Approved but has medium agreement with RNA expression and awaits external verification (HPA tissue IHC). Low tissue RNA specificity does not mean every cell should stain equally; interpret a local result against its named HPA cell population and appropriate controls (HPA tissue IHC; general IHC practice). |
| Membrane topology and compartment | UniProt annotates nuclear membrane and cytoplasm, with 3 transmembrane segments and regions facing the nucleoplasm or perinuclear space (UniProt Q96B42 topology). These annotations support considering a nuclear-rim pattern, but do not establish the catalog antibody’s epitope, antigen-retrieval needs, or a fixation effect (UniProt Q96B42 topology). |
| Isoforms and processing | UniProt lists 2 isoforms, a single chain spanning residues 1–140, and no annotated signal peptide, propeptide, glycosylation site, or modified residue (UniProt Q96B42). Without an epitope map, these entries cannot establish which isoforms an antibody detects or explain a particular section’s staining intensity (UniProt Q96B42). |
| Q: Should IF/ICC show the same compartment as tissue IHC? | A: HPA’s ICC-IF summary reports mainly mitochondria, with additional endoplasmic-reticulum localization, and rates those locations Approved; its tissue IHC instead reports predominantly cytoplasmic expression (HPA subcellular ICC-IF; HPA tissue IHC). Interpret each application against its own evidence and controls; the discrepancy remains unresolved by these records. |
| Situation | Likely cause | Next action |
|---|---|---|
| A reported High tissue has no visible chromogen in the named cell population. | The result diverges from HPA’s reference; tissue identity, reagent failure, or staining conditions could account for it (HPA tissue IHC; general IHC practice). | Confirm the named cell type on the section, inspect a positive control, and review the recorded IHC staining steps before changing one condition at a time (general IHC practice). |
| The whole section has diffuse brown haze. | Nonspecific detection or residual endogenous activity can obscure cell-associated staining (general IHC practice). | Compare a no-primary section, check blocking and detection controls, then score only signal distinguishable from that background (general IHC practice). |
| Nuclear stain dominates, without a convincing cytoplasmic pattern. | UniProt allows nuclear-membrane localization, but HPA tissue IHC describes predominantly cytoplasmic expression; the observed compartment needs verification (UniProt Q96B42; HPA tissue IHC). | Inspect whether staining follows the nuclear rim or fills nuclei, and compare controls and the HPA tissue pattern before assigning localization (general IHC practice; HPA tissue IHC). |
| Adipocytes or skeletal myocytes stain strongly. | Both are listed as Not detected in HPA tissue IHC; cross-reactivity or detection background is possible but unproven (HPA tissue IHC; general IHC practice). | Verify the cell type, inspect a no-primary control, and compare an HPA-reported High population in the same run (HPA tissue IHC; general IHC practice). |
| A weak signal appears in cerebral-cortex glial cells or bronchial ciliated-cell bodies. | HPA reports these populations at Low, so weak cell-associated staining may fit the reference (HPA tissue IHC). | Compare with controls and a reported High population; avoid treating Low as either a required strong positive or a definitive negative (HPA tissue IHC; general IHC practice). |
| An IF/ICC image seems inconsistent with the tissue-IHC call. | HPA reports mainly mitochondrial and additional endoplasmic-reticulum localization in ICC-IF, while tissue IHC is described as predominantly cytoplasmic (HPA subcellular ICC-IF; HPA tissue IHC). | Record the application and compartment separately, then judge each against its application-specific HPA description and controls (HPA subcellular ICC-IF; HPA tissue IHC; general IHC practice). |
Experiment evidence
IHC & IF images showing TMEM18 staining
A05347 · IHCImmunohistochemistry of TMEM18 in mouse brain tissue with TMEM18 antibody at 2.5 μg/mL.
A05347 · IFImmunofluorescence of TMEM18 in Mouse Brain cells with TMEM18 antibody at 20 μg/mL.
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000151353-TMEM18/tissue/cerebral+cortex#imid_10580861
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000151353-TMEM18/tissue/colon#imid_10580795
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000151353-TMEM18/tissue/liver#imid_10580780
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000151353-TMEM18/tissue/kidney#imid_10580781
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA040233; green = TMEM18, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA040233; green = TMEM18, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for TMEM18 IHC & IF
🧪Run pancreas first: exocrine glandular cells should stain (HPA: High in pancreas exocrine glandular cells). Use adipose tissue as the negative: adipocytes are expected to lack staining (HPA: Not detected in adipocytes); on the pancreas slide, assess adjacent cells that remain unstained as internal negatives without assigning them an unreported cell identity.
Positive control tissue: Epididymis (Glandular cells, HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show TMEM18 in A-431, U-251MG, U2OS, with annotated localisation: Mitochondria (approved) (HPA subcellular).
Technical controls: Include no-primary (secondary-only) and host-species- and clonality-matched isotype controls, plus TMEM18-knockout tissue if available (standard IHC practice). Check for endogenous biotin background if using avidin–biotin detection in pancreas (standard IHC practice).
⚠️Feasibility: A TMEM18-specific fixation window and retrieval dependency are unreported in the supplied evidence; the A05347 mouse-brain IHC caption reports 2.5 µg/mL but does not report a fixative (A05347 tissue-IHC caption). The evidence does not establish whether frozen sections or IF/ICC are easier than paraffin IHC. Pancreatic endogenous biotin may complicate avidin–biotin detection, so interpret staining against the matched controls (standard IHC practice).
HPA tissue IHC evidence for TMEM18
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Approved — 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 |
|---|---|---|---|---|
| Epididymis | Glandular cells | High | Protein (IHC) | HPA → |
| Pancreas | Exocrine glandular cells | High | Protein (IHC) | HPA → |
| Placenta | Trophoblastic cells | High | Protein (IHC) | HPA → |
| Salivary gland | Glandular cells | High | Protein (IHC) | HPA → |
| Seminal vesicle | Glandular cells | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Adrenal gland | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Esophagus | Squamous epithelial cells | Not detected | Protein (IHC) | HPA → |
| Hippocampus | Glial cells | Not detected | Protein (IHC) | HPA → |
| Oral mucosa | Squamous epithelial cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced TMEM18 IHC Tips
Use compartment and cell type controls when interpreting TMEM18 staining: tissue and subcellular observations differ across sources (UniProt Q96B42; HPA tissue IHC; HPA subcellular).
What retrieval should I start with for weak TMEM18 staining in paraffin sections?
Start with Tris-EDTA pH 9.0 HIER at 95–98 °C for 20 min (page retrieval specification). Let sections cool in retrieval buffer, then compare staining with a matched section processed without primary antibody to assess detection background (standard IHC practice). Keep section thickness, heating vessel, and cooling time consistent across samples, since uneven retrieval can create regional differences in chromogenic intensity (standard IHC practice). TMEM18 has 3 membrane-spanning segments, so antibody access may depend on the recognized epitope, which is unspecified here (UniProt Q96B42 topology). If staining remains weak, test a milder retrieval condition on adjacent sections while holding antibody concentration and detection constant (standard IHC practice).
How should I troubleshoot TMEM18 staining when fixation history is uncertain?
Target-specific fixation sensitivity is unknown: the selected mouse brain IHC caption gives 2.5 µg/mL antibody but does not state a fixative (A05347 tissue-IHC caption). Record fixation method and duration for every block, then compare similarly processed sections in the same staining run (standard IHC practice). Begin with the specified Tris-EDTA pH 9.0 retrieval at 95–98 °C for 20 min (page retrieval specification). If staining varies between blocks, inspect tissue preservation and run a no-primary control before attributing differences to TMEM18 abundance (standard IHC practice). Neither the reported tissue pattern nor the protein topology establishes a TMEM18-specific fixation effect (HPA tissue IHC; UniProt Q96B42 topology).
Which TMEM18 staining pattern should I accept in chromogenic IHC?
Assess staining by cell type and compartment separately: tissue IHC reports mainly cytoplasmic expression, while UniProt lists cytoplasm and nuclear membrane (HPA tissue IHC; UniProt Q96B42 subcellular). Subcellular IF instead reports mitochondria as the main location and endoplasmic reticulum as an additional location (HPA subcellular). Because these sources differ, do not call a perinuclear rim, diffuse cytoplasm, or puncta specific from morphology alone (HPA tissue IHC; HPA subcellular; UniProt Q96B42). Compare matched sections stained without primary antibody and check whether the pattern repeats across intact cells (standard IHC practice). Document the observed compartment explicitly rather than combining nuclear membrane and cytoplasmic signal into one score (standard IHC practice).
Could epitope position explain discordant TMEM18 IHC results?
TMEM18 has 2 annotated isoforms and 3 transmembrane segments at residues 26–46, 53–73, and 92–112 (UniProt Q96B42). Its annotated topology places residues 47–52 and 113–140 on the nuclear side, while other listed loops face the perinuclear space (UniProt Q96B42 topology). Check the antibody's stated immunogen or mapped epitope before comparing staining across reagents; that information is absent from this payload (supplied antibody evidence). A missing or altered epitope in an isoform could change staining, but isoform-specific epitope coverage is not established here (UniProt Q96B42 isoforms; supplied antibody evidence). Keep retrieval and detection matched during reagent comparisons, and report each reagent's staining pattern separately (standard IHC practice).
How can IF help investigate an ambiguous TMEM18 IHC pattern?
Use IF on a parallel specimen to compare TMEM18 signal with a glandular epithelial marker where glandular cells are expected to stain (HPA tissue IHC; standard IF practice). Choose a far-red fluorophore if the tissue shows strong shorter-wavelength autofluorescence, and include single-color and no-primary controls for multiplex interpretation (standard IF practice). TMEM18 spans membranes 3 times, with annotated nuclear-facing and perinuclear-facing regions, so set permeabilisation according to the antibody's mapped epitope (UniProt Q96B42 topology). If that epitope is unknown, compare mild and stronger permeabilisation on matched preparations without assigning a particular membrane side to the antibody (standard IF practice). Compare any punctate signal with the reported mitochondrial and endoplasmic reticulum locations, while recognizing that these IF observations differ from tissue IHC (HPA subcellular; HPA tissue IHC).
What controls distinguish TMEM18 staining from chromogenic background?
Run a no-primary section through the same secondary reagent and chromogen steps to reveal detection background (standard IHC practice). Use a peroxidase block before DAB development, and check whether pigment or endogenous enzyme activity persists in control sections (standard chromogenic IHC practice). If diffuse staining rises with antibody concentration, titrate the primary on adjacent sections while keeping retrieval, incubation, and DAB development fixed (standard IHC practice). HPA reports high staining in pancreatic exocrine glandular cells and no detection in adipocytes, which provides cell-specific comparison points rather than absolute controls (HPA tissue IHC). Score only signal above matched background within preserved cells, excluding folds, tissue edges, and damaged areas (standard IHC practice).
How should I quantify TMEM18 staining across paraffin sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the compartment and cell population before scoring, because tissue IHC describes mainly cytoplasmic staining while other localisation records differ (HPA tissue IHC; HPA subcellular; UniProt Q96B42). For a selected cell population, report the percentage of positive cells and an H-score based on intensity categories 0–3 (standard IHC scoring practice). Normalize positive counts to all evaluable cells of that population, or report positive-cell density per mm² of viable tissue (standard IHC scoring practice). Keep retrieval, imaging exposure, counterstain, and chromogen development consistent between sections (standard IHC practice). Record cell type and tissue separately: glandular cells can stain highly in several tissues, whereas glial cells are reported low or undetected in listed brain regions (HPA tissue IHC).
When is an apparent TMEM18-positive cell likely an artefact?
Treat signal confined to tissue edges, folds, or necrotic areas as suspect, especially if the no-primary section shows similar DAB deposition (standard IHC practice). Check cell identity: HPA reports high staining in several glandular populations but no detection in adipocytes and selected squamous epithelial cells (HPA tissue IHC). Check compartment too, since tissue IHC mainly reports cytoplasm, UniProt includes nuclear membrane, and subcellular IF reports mitochondria and endoplasmic reticulum (HPA tissue IHC; UniProt Q96B42; HPA subcellular). A strong isolated nuclear stain outside those documented patterns needs independent confirmation, including a matched control section (standard IHC practice). Persistent staining after omission of primary antibody suggests background from detection reagents or endogenous enzyme rather than evidence of TMEM18 (standard chromogenic IHC practice).
Boster reagents
Best TMEM18 / Transmembrane protein 18 IHC Antibodies
A05347 has IHC data from mouse brain tissue and IF data from mouse brain cells (catalog image captions); it lists human, mouse and rat reactivity (catalog: reactivity).
Real IHC data
Anti-Transmembrane protein 18 TMEM18 Antibody
Cat # A05347
A05347 is listed for IHC-P and IF (catalog: applications), with IHC shown in mouse brain tissue at 2.5 μg/mL (IHC image caption). Its IF image shows mouse brain cells at 20 μg/mL (IF image caption); the catalog lists human, mouse and rat reactivity (catalog: reactivity).
Which to pick: Choose A05347 for paraffin-section IHC (catalog: IHC-P); its mouse brain tissue image uses 2.5 μg/mL, and the fixative is unreported (IHC image caption). Choose A05347 for IF in mouse brain cells (IF image caption: 20 μg/mL); ICC validation is unreported (catalog: applications). For cross-species work, A05347 lists human, mouse and rat reactivity (catalog: reactivity), while the supplied IHC and IF images show mouse samples (image captions); its host is rabbit and its clonality is unreported (catalog: host and clone).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry Q96B42 (TMM18_HUMAN, Transmembrane protein 18).
- Human Protein Atlas. TMEM18 tissue IHC expression (reliability: Approved).
- Human Protein Atlas. TMEM18 subcellular location (ICC-IF): Mainly localized to the mitochondria. In addition localized to the endoplasmic reticulum..
- Human Protein Atlas. TMEM18 antibody validation summary (1 antibodies).
- Identification of protein-coding genes associated with metastatic prostate cancer. Endocrine-related cancer 2025 — PMC12203752.
- The obesity gene, TMEM18, is of ancient origin, found in majority of neuronal cells in all major brain regions and associated with obesity in severely obese children. BMC medical genetics 2010 — PMC2858727.
- PubMed PMID:17974005 — UniProt-cited evidence.
- PubMed PMID:15815621 — UniProt-cited evidence.
- PubMed PMID:15489334 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for TMEM18 (Transmembrane protein 18). Expected localisation Cytoplasmic staining (HPA tissue IHC); nuclear membrane expected (UniProt). Antigen retrieval: Tris-EDTA pH 9.0 HIER, 95–98 °C, 20 min (rule: nuclear antigen). Validated IHC antibody: A05347 at 2.5 μg/mL (the product's own IHC validation image is shown). Controls (HPA): positive Epididymis (Glandular cells); negative Adipose tissue. IHC workflow; specimen preparation unspecified. Protocol steps: 1. Sample: Tissue sections; selected-image fixative not specified (standard IHC workflow); 2. Fixation: Image fixative and duration unreported (datasheet A05347); 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-TMEM18, 2.5 μg/mL (datasheet A05347); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: Keep fixation consistent across sections (standard IHC practice; not target-specific); Caveat: Medium staining–RNA consistency; verify signal (HPA tissue IHC); Isoform / epitope: 2 isoforms; epitope coverage is unknown (UniProt); Regulation: No staining-linked regulation annotated (UniProt). Evidence: UniProt Q96B42, HPA tissue IHC · Approved, HPA ICC-IF · Mainly localized to the mitochondria. In addition localized to the…, Datasheet A05347, PMC12203752. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/TMEM18/immunohistochemistry-ihc-guide.