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CALHM1 / Calcium homeostasis modulator protein 1 · IHC design guide
Design Immunohistochemistry for CALHM1
Plan CALHM1 paraffin IHC around cytoplasmic staining in subsets of neurons and adrenal gland cells (HPA tissue IHC). This guide covers fixation consistency, controls and the catalog antibody’s 5 μg/mL IHC starting concentration (standard IHC practice; datasheet: 5 μg/mL).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CALHM1 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 | Cytoplasm observed (HPA tissue IHC); cell and ER membranes annotated (UniProt) | |
| Staining pattern | Subset of neurons and adrenal cells stains cytoplasmically (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen) | |
| Positive control | Cerebral cortex | |
| 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 | Staining varies by cell subset; antibody–RNA consistency is medium (HPA tissue IHC) | |
| Regulation | Brain-enhanced RNA expression (HPA tissue RNA) | |
| Isoform / epitope | No isoforms annotated; epitope accessibility depends on loop orientation (UniProt) |
Section 1
Recommended CALHM1 IHC & IF Protocols
The catalog antibody has an IHC-P protocol; the published CALHM1 protocol below uses chromogenic staining of taste bud-containing vibratome sections (PMC5966022).
| Sample | Tissue sections; selected-image fixative not specified (standard IHC workflow) |
| Fixation | Image fixative and duration unreported (datasheet A03599-1); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat-induced epitope retrieval in citrate buffer, pH 6.0, 20 min at 95–98 °C (standard rule: cytoplasmic / membrane 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-CALHM1, 5 μg/mL (datasheet A03599-1) |
| Primary incubation | Overnight at 4 °C (standard) |
| Detection | HRP-polymer secondary, DAB chromogen 5–10 min (standard) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | CALHM1-positive staining in neuronal cells of cerebral cortex (HPA tissue IHC: Medium). HPA tissue profile: Cytoplasmic expression in a subset of neurons and a subset of adrenal gland cells. No signal in the no-primary control. |
💡Decision noteFor paraffin sections, start with citrate pH 6.0 retrieval at 95–98 °C for 20 min (page antigen retrieval). The published vibratome method uses different conditions (PMC5966022).
Section 2
What Is the Expected CALHM1 Staining Pattern?
CALHM1 is a four-pass protein annotated at the cell, basolateral and endoplasmic reticulum membranes (UniProt Q8IU99 topology and subcellular location). In paraffin-section IHC, expect staining in a subset of cerebral cortex neurons, with an observed cytoplasmic pattern and medium intensity (HPA tissue IHC: neuronal cells, Medium). HPA rates the tissue staining Enhanced, while reporting medium consistency with RNA expression (HPA tissue IHC: reliability).
| Selective cytoplasmic staining in some cerebral cortex neurons, with unstained neighbors. | This matches the reported distribution and medium staining level (HPA tissue IHC: cerebral cortex neuronal cells). A cytoplasmic appearance can include unresolved intracellular membranes; the IHC image pattern alone does not identify a specific membrane (UniProt Q8IU99 subcellular location; HPA tissue IHC: profile). |
| A membrane-associated signal accompanies staining in the expected neuronal population. | Cell and endoplasmic reticulum membranes are annotated locations (UniProt Q8IU99 subcellular location). Judge it alongside the observed cytoplasmic IHC profile; a crisp membrane outline is not required by the supplied tissue result (HPA tissue IHC: profile). |
| Strong signal is confined to nuclei or another compartment outside the annotated membrane locations. | This does not fit the reported cytoplasmic IHC pattern or membrane annotations (HPA tissue IHC: profile; UniProt Q8IU99 subcellular location). Treat it as suspect and check controls before assigning it to CALHM1 (general IHC practice). |
| Strong staining appears broadly in cells reported as unstained, such as appendix glandular cells. | HPA reports no detection in those cells (HPA tissue IHC: appendix glandular cells). Check antibody specificity and endogenous detection activity; the tissue-level observation alone cannot identify which caused the signal (general IHC practice). |
| Color is diffuse across tissue, including spaces between cells. | This lacks the selective cellular pattern reported for CALHM1 (HPA tissue IHC: profile). Review background and detection controls before scoring any cells positive (general IHC practice). |
💡Expected CALHM1 appearanceCall positive when a subset of cerebral cortex neurons shows selective, approximately medium cytoplasmic staining (HPA tissue IHC: cerebral cortex); widespread strong staining of reported negative cell populations is suspect (HPA tissue IHC: negative cells).
| Tissue and cell choice | Adult brain predominance is annotated by UniProt, and cerebral cortex neurons show medium IHC staining (UniProt Q8IU99 tissue specificity; HPA tissue IHC: cerebral cortex). HPA calls adrenal gland glandular cells Low, so a faint result there needs cautious interpretation (HPA tissue IHC: adrenal gland). |
| Antibody validation | The listed antibody HPA061816 has Enhanced IHC status, while HPA describes medium staining-to-RNA consistency (HPA antibodies: HPA061816; HPA tissue IHC: reliability). Neither designation proves that every stained cell is specific (general IHC interpretation). |
| Topology and epitope access | CALHM1 has 4 transmembrane segments and both cytoplasmic and extracellular regions (UniProt Q8IU99 topology). The supplied record does not locate this antibody’s epitope, so it cannot justify a CALHM1-specific retrieval or permeabilisation setting. |
| Processing and variants | UniProt lists a full-length 1–346 chain, no signal peptide or propeptide, and no annotated isoforms (UniProt Q8IU99 processing and isoforms). These annotations provide no basis for expecting a shed fragment or a second isoform-specific IHC pattern. |
| IF/ICC Q: Can its staining pattern be inferred here? | A: HPA summarizes the subcellular location as membrane but provides no ICC-IF image-bearing cell lines (HPA subcellular: summary and images). This does not establish an IF/ICC staining pattern or an IF protocol; consult the separate IF/ICC guide. |
| Situation | Likely cause | Next action |
|---|---|---|
| No signal in cerebral cortex neurons. | The reference result is medium, restricted to a subset of neurons (HPA tissue IHC: cerebral cortex); sampling or an ineffective IHC detection run may explain absence (general IHC practice). | Confirm neuronal regions and section quality; run appropriate positive and detection controls, then review retrieval and detection settings under the antibody’s IHC-P instructions (general IHC practice). |
| Only a few neurons stain. | Staining of a subset, rather than every neuron, is the reported pattern (HPA tissue IHC: profile). | Score cell type, distribution and intensity before changing conditions; compare with a reported negative cell population on the same run (HPA tissue IHC: negative cells; general IHC practice). |
| Strong nuclear staining dominates. | Nuclear localisation is outside the supplied membrane annotations and observed cytoplasmic IHC profile (UniProt Q8IU99 subcellular location; HPA tissue IHC: profile). | Inspect a no-primary control and repeat with the IHC-validated antibody; avoid scoring isolated nuclear color as CALHM1 (general IHC practice). |
| Appendix glandular cells stain strongly. | HPA reports no detection in these cells; cross-reactivity or endogenous detection activity is possible, but unproven (HPA tissue IHC: appendix glandular cells; general IHC practice). | Check no-primary and detection controls, then compare the same run with cerebral cortex neurons (general IHC practice; HPA tissue IHC: cerebral cortex). |
| Diffuse color obscures cell boundaries. | The observed reference pattern is selective cytoplasmic staining, so diffuse color limits interpretation (HPA tissue IHC: profile). | Check blocking, washes, detection exposure and counterstain using the same control sections; score only resolvable cellular signal (general IHC practice). |
| Adrenal gland gives faint or absent staining. | HPA rates glandular cells Low, making this a weak reference tissue (HPA tissue IHC: adrenal gland). | Use cerebral cortex neurons as the stronger comparison and retain matched negative controls; do not infer a CALHM1-specific fixation effect from this result (HPA tissue IHC: cerebral cortex and adrenal gland). |
Experiment evidence
IHC & IF images showing CALHM1 staining
A03599-1 · IHCImmunohistochemistry of CALHM1 in rat liver tissue with CALHM1 antibody at 5 μg/mL.
A03599-1 · IFImmunofluorescence of CALHM1 in Rat Liver cells with CALHM1 antibody at 20 μg/mL.
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000185933-CALHM1/tissue/cerebral+cortex#imid_1292
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000185933-CALHM1/tissue/cerebral+cortex#imid_20539947
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000185933-CALHM1/tissue/colon#imid_20539865
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000185933-CALHM1/tissue/liver#imid_20539866
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CALHM1 IHC & IF
🧪Run cerebral cortex first; neuronal cells should stain at the HPA Medium level (HPA: cerebral cortex neuronal cells, Medium). Use adipose tissue as the negative tissue, with adipocytes expected to show no detectable staining (HPA: adipose adipocytes, Not detected); on the cortex slide, compare neuronal staining with adjacent non-neuronal cells as a background check, without assuming those cells are CALHM1-negative (HPA: cortex row specifies neuronal cells only).
Positive control tissue: Cerebral cortex (Neuronal cells, HPA Medium)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA carries no ICC-IF cell line for CALHM1; derive a cell-line control from the positive tissue's cell type (Neuronal cells) and confirm it by RNA or western blot first.
Technical controls: Include a no-primary, secondary-only control; an isotype control matched to the primary antibody’s host species and immunoglobulin class; and CALHM1-knockout tissue, if available, as a biological specificity control (standard IHC practice). For chromogenic cortex IHC, block endogenous peroxidase and inspect vessel-associated background (standard IHC practice).
⚠️Feasibility: A target-specific fixation window and the effect of antigen retrieval are unreported in the supplied target and application evidence; optimize retrieval empirically (supplied evidence: no fixation-window or retrieval comparison). The selected rat-liver IHC caption reports 5 µg/mL but leaves the fixative unreported (selected SKU A03599-1 caption). The supplied evidence does not establish whether frozen sections or IF are easier than paraffin IHC; cortical lipofuscin can complicate IF interpretation through autofluorescence (HPA: no ICC-IF cell-line images; standard IF practice).
HPA tissue IHC evidence for CALHM1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — Medium 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 |
|---|---|---|---|---|
| Cerebral cortex | Neuronal cells | Medium | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Appendix | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | Not detected | Protein (IHC) | HPA → |
| Breast | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Bronchus | Respiratory epithelial cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced CALHM1 IHC Tips
Troubleshoot CALHM1 staining in paraffin sections by checking retrieval, cellular location, controls, and scoring before interpreting chromogenic signal.
How should I retrieve CALHM1 antigen in paraffin sections?
Use citrate buffer at pH 6.0 for heat-induced retrieval at 95–98 °C for 20 min (page retrieval specification). Let sections cool in buffer, then compare a retrieved section with an otherwise matched section lacking retrieval to assess whether the treatment improves specific cellular staining (standard IHC practice). If staining remains weak, test a more alkaline retrieval buffer only as a fallback, holding section thickness, antibody concentration, and detection conditions constant (standard IHC practice). Judge improvement against staining in the expected neuronal population rather than diffuse tissue color, because the reported tissue pattern is restricted to a subset of neurons (HPA tissue IHC).
Could fixation be masking CALHM1 in my IHC sections?
Target-specific fixation sensitivity is unknown: the selected rat liver IHC caption reports 5 µg/mL antibody but does not state a fixative (selected SKU A03599-1 tissue-IHC caption). Record the actual fixative and fixation duration for each block before comparing staining across specimens, and keep section thickness and retrieval conditions matched (standard IHC practice). If signal varies between blocks, assess preservation and staining together on adjacent sections; weak staining alone cannot establish that fixation masked the epitope (standard IHC practice). Do not infer a CALHM1-specific fixation effect from tissue staining patterns or membrane topology, which provide different kinds of evidence (HPA tissue IHC; UniProt Q8IU99 topology).
Where should convincing CALHM1 staining appear?
Examine neuronal cell bodies and their boundaries in cerebral cortex, where medium staining of neuronal cells is reported, rather than assuming every cell should stain (HPA tissue IHC). CALHM1 is annotated at the cell, basolateral, and endoplasmic reticulum membranes, so membrane-associated or intracellular staining may be plausible depending on epitope accessibility and tissue context (UniProt Q8IU99 subcellular location). The reported tissue IHC pattern is cytoplasmic in a subset of neurons and adrenal gland cells; use that observation when reviewing chromogenic sections (HPA tissue IHC). Compare stained cells with adjacent morphology and a negative control, since diffuse extracellular deposits do not establish the annotated cellular location (standard IHC practice; UniProt Q8IU99 subcellular location).
How does epitope position affect CALHM1 staining?
Confirm the catalog antibody’s immunogen or mapped epitope before interpreting staining, because the supplied record identifies 4 transmembrane segments with cytoplasmic and extracellular regions (UniProt Q8IU99 topology). Its long cytoplasmic region spans residues 207–346, while the extracellular region at 126–180 includes a glycosylation site at residue 140 (UniProt Q8IU99 topology and glycosylation). Retrieval can change epitope accessibility, so compare controlled retrieval conditions if staining is weak, without assuming which side of the membrane this antibody recognizes (standard IHC practice). The record annotates 0 isoforms; that annotation does not substitute for antibody specificity controls or establish an epitope (UniProt Q8IU99 isoforms; standard IHC practice).
How can I adapt CALHM1 assessment to multiplex IF?
On the separate IF/ICC guide, pair CALHM1 with a marker that identifies the expected neuronal population when studying brain, and score colocalization at the cell level (HPA tissue IHC; standard IF practice). Choose spectrally separated fluorophores and inspect unstained tissue in each channel first, because tissue autofluorescence can mimic weak signal (standard IF practice). Set permeabilisation according to the antibody’s mapped epitope: a cytoplasmic epitope requires membrane access, whereas an extracellular epitope may be assessed without permeabilisation (UniProt Q8IU99 topology; standard IF practice). Compare matched permeabilised and nonpermeabilised samples before interpreting membrane versus intracellular fluorescence; the supplied HPA subcellular record lists no ICC/IF images for validation (HPA subcellular record; standard IF practice).
How do I reduce diffuse chromogenic background?
First inspect a no-primary control and the tissue edges to distinguish nonspecific chromogen deposition from cellular staining (standard IHC practice). Block endogenous peroxidase before enzyme-based detection, use an appropriate protein block, and titrate the primary antibody and development time if background persists (standard IHC practice). The selected rat liver caption documents 5 µg/mL for its image, but that concentration is a reference point rather than a validated setting for every tissue (selected SKU A03599-1 tissue-IHC caption; standard IHC practice). Require cellular signal above matched controls before calling a sample positive, particularly when the expected tissue pattern involves only a subset of neurons (HPA tissue IHC; standard IHC practice).
What is a defensible way to score CALHM1 IHC? ⚠ ANSWER MARKED FOR VERIFICATION
Define the analysis compartment and eligible cell population before scoring; in cerebral cortex, assess neuronal cells because that is the reported positive population (HPA tissue IHC). Record the percentage of positive eligible cells and staining intensity separately, or calculate an H-score on a consistent 0–300 scale using prespecified intensity bins (standard IHC practice). For spatial analysis, report positive neuronal cells per mm² of evaluable tissue and exclude folds, necrosis, and section edges consistently (standard IHC practice). Normalize counts to the number of eligible cells or evaluable area, retain the same detection threshold across slides, and report background-control signal alongside scores (standard IHC practice).
When is a CALHM1-positive IHC result credible?
Look for reproducible staining in appropriately shaped cells, especially the neuronal subset reported in cerebral cortex, with signal exceeding matched negative controls (HPA tissue IHC; standard IHC practice). Interpret cellular staining in light of CALHM1’s annotated cell membrane, basolateral membrane, and endoplasmic reticulum membrane locations and the cytoplasmic pattern reported by tissue IHC (UniProt Q8IU99 subcellular location; HPA tissue IHC). Treat staining confined to section edges, necrotic areas, or extracellular deposits as suspect, and check a no-primary control for endogenous enzyme signal (standard IHC practice). Liver staining shown for the selected antibody at 5 µg/mL documents an image condition; confirm cell identity and controls before generalizing that observation (selected SKU A03599-1 tissue-IHC caption; standard IHC practice).
Boster reagents
Best CALHM1 / Calcium homeostasis modulator protein 1 IHC Antibodies
A03599-1 is listed for IHC-P and IF in human, mouse and rat (catalog: applications, reactivity), with pictured results in rat liver tissue and rat liver cells (catalog: image captions).
Real IHC data
Anti-CALHM1 Antibody
Cat # A03599-1
A03599-1 will render with an IHC figure from rat liver tissue at 5 μg/mL (catalog: IHC image caption). The same SKU has a separate IF figure from rat liver cells at 20 μg/mL (catalog: IF image caption).
Which to pick: For paraffin-section IHC, choose A03599-1 (catalog: IHC-P application); its own IHC caption shows rat liver tissue, but does not report the fixative (catalog: IHC image caption). For IF, choose A03599-1 based on its rat liver cell figure (catalog: IF image caption); ICC validation is unreported (catalog: applications, image captions). For cross-species work, A03599-1 lists human, mouse and rat reactivity, while its pictured IHC and IF results are rat only; clonality is unreported (catalog: reactivity, image captions, clone field).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry Q8IU99 (CAHM1_HUMAN, Calcium homeostasis modulator protein 1).
- Human Protein Atlas. CALHM1 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. CALHM1 subcellular location (ICC-IF): Membrane.
- Human Protein Atlas. CALHM1 antibody validation summary (1 antibodies).
- Chemical synapses without synaptic vesicles: Purinergic neurotransmission through a CALHM1 channel-mitochondrial signaling complex. Science signaling 2018 — PMC5966022.
- Taste cells depend on axon proximity to generate presynaptic sites. PloS one 2025 — PMC12132963.
- Structural comparisons of human and mouse fungiform taste buds. bioRxiv : the preprint server for biology 2024 — PMC11275760.
- Expression of genes encoding multi-transmembrane proteins in specific primate taste cell populations. PloS one 2009 — PMC2780358.
- PubMed PMID:15164054 — UniProt-cited evidence.
- PubMed PMID:15489334 — UniProt-cited evidence.
- PubMed PMID:18585350 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CALHM1 (Calcium homeostasis modulator protein 1). Expected localisation Cytoplasm observed (HPA tissue IHC); cell and ER membranes annotated (UniProt). Antigen retrieval: Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen). Validated IHC antibody: A03599-1 at 5 μg/mL (the product's own IHC validation image is shown). Controls (HPA): positive Cerebral cortex (Neuronal 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 A03599-1); verify before use.; 3. Sectioning: 4–5 µm sections on charged slides (standard); 4. Deparaffinisation: Xylene, graded ethanol series to water (standard); 5. Antigen retrieval: Heat-induced epitope retrieval in citrate buffer, pH 6.0 , 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-CALHM1, 5 μg/mL (datasheet A03599-1); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: Keep fixation consistent across sections (standard IHC practice; not target-specific); Caveat: Staining varies by cell subset; antibody–RNA consistency is medium (HPA tissue IHC); Isoform / epitope: No isoforms annotated; epitope accessibility depends on loop orientation (UniProt); Regulation: Brain-enhanced RNA expression (HPA tissue RNA). Evidence: UniProt Q8IU99, HPA tissue IHC · Enhanced, HPA ICC-IF · Membrane, Datasheet A03599-1, PMC5966022. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CALHM1/immunohistochemistry-ihc-guide.