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CALHM1 / Calcium homeostasis modulator protein 1 · IHC design guide
Design Immunohistochemistry for CALHM1
Use cytoplasmic staining in a subset of neurons as the CALHM1 tissue IHC benchmark (HPA tissue IHC). Start the catalog antibody at 5 μg/mL (datasheet), and score positive cells against a no-primary control (standard IHC practice).
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 | Cytoplasmic in tissue; membrane and ER localisation annotated (HPA tissue IHC; UniProt) | |
| Staining pattern | Cytoplasmic staining in subsets of neurons and adrenal cells (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 | Subset staining can make whole-field scoring misleading (HPA tissue IHC) | |
| Regulation | Predominantly expressed in adult brain (UniProt) | |
| Isoform / epitope | No isoforms or cleavage annotated; epitope side depends on topology (UniProt) |
Section 1
Recommended CALHM1 IHC & IF Protocols
The catalog antibody’s IHC-P protocol is paired with one published CALHM1 chromogenic protocol using taste bud 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 HIER at 95–98 °C for 20 min (page retrieval rule); the published protocol used 85 °C for 10 min (PMC5966022).
Section 2
What Is the Expected CALHM1 Staining Pattern?
CALHM1 is a four-pass protein assigned to the cell, endoplasmic reticulum and basolateral membranes (UniProt Q8IU99 topology and subcellular location). In tissue IHC, expect cytoplasmic staining in a subset of neurons, especially in cerebral cortex, with weaker staining in a subset of adrenal gland cells (HPA: tissue IHC). HPA rates its tissue profile Enhanced but reports only medium consistency between antibody staining and RNA expression (HPA: reliability description).
| Subset of cortical neuronal cells shows moderate cytoplasmic chromogen, while neighboring cells differ in intensity. | This matches the observed positive tissue pattern: neuronal staining is Medium in cerebral cortex, and expression is limited to a subset of neurons (HPA: cerebral cortex; HPA: tissue profile). Cytoplasmic appearance in a section does not by itself resolve the cell membrane from intracellular membranes (UniProt Q8IU99 subcellular location; general IHC practice). |
| Staining follows cell outlines or appears within neuronal cytoplasm, with no dominant nuclear signal. | Membrane and endoplasmic reticulum localization make those distributions biologically plausible (UniProt Q8IU99 subcellular location). A dominant nuclear pattern falls outside the supplied localization evidence; assess it as a possible staining artefact before calling it CALHM1 (UniProt Q8IU99 subcellular location; general IHC practice). |
| Strong staining appears in adipocytes, appendix glandular cells or marrow hematopoietic cells. | These specified cell populations are Not detected in HPA tissue IHC (HPA: adipose tissue; HPA: appendix; HPA: bone marrow). Treat unexpected staining as possible cross-reactivity or endogenous detection activity, then check controls; an entire tissue is not necessarily a negative control for every cell type (general IHC practice). |
| Chromogen covers many cell types and extracellular areas with little distinction between structures. | A diffuse field is difficult to reconcile with the reported subset-of-neurons pattern (HPA: tissue profile). Check staining without primary antibody, blocking and chromogen development to distinguish nonspecific or detection background from a cell-associated signal (general IHC practice). |
| No neuronal staining is visible in a cerebral cortex section included as a positive control. | HPA reports Medium staining in cortical neuronal cells, so an absent signal calls for a run-level check (HPA: cerebral cortex). Confirm tissue identity and preservation, then review retrieval, primary-antibody conditions and detection controls before interpreting a study sample as negative (general IHC practice). |
💡Expected CALHM1 appearanceCall a positive result when a subset of cortical neurons has moderate cytoplasmic, potentially membrane-associated staining (HPA: cerebral cortex and tissue profile; UniProt Q8IU99 subcellular location); dominant nuclear or widespread uniform staining warrants a specificity check (general IHC practice).
| Membrane topology and epitope access (UniProt Q8IU99 topology) | CALHM1 has four transmembrane spans, cytoplasmic segments, and two extracellular loops (UniProt Q8IU99 topology). Which domain an antibody recognizes can affect access in an assay, but the supplied sources give no antibody epitope; do not prescribe permeabilisation or predict retrieval response from topology alone (general IHC practice). |
| Cell and tissue distribution (HPA: tissue IHC; UniProt Q8IU99 tissue specificity) | HPA shows Medium cortical neuronal staining and Low adrenal glandular-cell staining, with only subsets positive (HPA: cerebral cortex; HPA: adrenal gland; HPA: tissue profile). UniProt reports predominant adult-brain expression and expression in circumvallate taste bud cells; no taste-bud IHC result is supplied here (UniProt Q8IU99 tissue specificity). |
| Evidence strength (HPA: reliability description; HPA: HPA061816 IHC Enhanced) | The listed antibody, HPA061816, has an Enhanced IHC validation status, while HPA describes medium consistency with RNA expression for the tissue profile (HPA: HPA061816; HPA: reliability description). Use the reported cell pattern as a reference, and retain controls when judging staining outside it (general IHC practice). |
| Processing and glycosylation (UniProt Q8IU99 processing and glycosylation) | UniProt lists a single 1–346 chain, no signal peptide or propeptide, and one glycosylation site at residue 140 (UniProt Q8IU99 processing and glycosylation). These annotations do not identify the antibody epitope or establish a target-specific fixation or antigen-retrieval effect (general IHC practice). |
| IF/ICC localization evidence (HPA: subcellular summary) | HPA summarizes CALHM1 as Membrane for ICC-IF, but lists no main location or cell-line images in the supplied record (HPA: subcellular summary). That summary supports a localization expectation, not a demonstrated IF staining example or an IF protocol (HPA: subcellular summary). |
| Situation | Likely cause | Next action |
|---|---|---|
| Cortical neurons are unstained while the section otherwise develops. | The run may have insufficient target detection, or the selected field may miss the positive neuronal subset (HPA: cerebral cortex and tissue profile; general IHC practice). | Inspect several appropriate cortical fields and tissue quality. Review the IHC antibody instructions, retrieval conditions and detection reagents with a positive-control section before scoring the sample negative (general IHC practice). |
| Adrenal staining looks faint relative to cortical staining. | Low glandular-cell staining in the adrenal gland versus Medium cortical neuronal staining is consistent with the supplied observations (HPA: adrenal gland; HPA: cerebral cortex). | Compare like cell populations and use a cortical positive control to judge whether the run worked; avoid forcing both tissues to the same intensity by extending chromogen development (HPA: tissue IHC; general IHC practice). |
| Signal is predominantly nuclear. | The supplied locations are cell, endoplasmic reticulum and basolateral membranes; a nuclear pattern is unsupported (UniProt Q8IU99 subcellular location). | Review section morphology, primary-antibody specificity and a no-primary control. Record nuclear signal separately rather than counting it as the expected CALHM1 pattern (general IHC practice). |
| Adipocytes or appendix glandular cells stain strongly. | Those cell populations are reported as Not detected, making cross-reactivity or endogenous detection activity possibilities (HPA: adipose tissue; HPA: appendix; general IHC practice). | Check a no-primary control and the detection-system controls, then compare the distribution with a cortical positive control before interpreting the unexpected staining (general IHC practice). |
| Background obscures differences between cells. | Nonspecific antibody binding, endogenous detection activity or excessive chromogen development can obscure a subset pattern (HPA: tissue profile; general IHC practice). | Check a no-primary section; review blocking, primary-antibody concentration, washing and development time under the assay's validated conditions (general IHC practice). |
| Q: Can this IHC result be used as an IF/ICC pattern reference? | HPA gives a Membrane ICC-IF summary but supplies no main location or cell-line images here (HPA: subcellular summary). | A: Use membrane localization as a cautious expectation and assess IF/ICC with its own controls and guide; this tissue IHC pattern alone does not establish an IF/ICC result (HPA: subcellular summary; general IF practice). |
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, where adipocytes are not detected (HPA: adipose tissue, adipocytes, Not detected); neighboring cells on the cortex slide that lack specific staining should show only background signal, without assigning them a CALHM1-negative identity (internal control: background assessment).
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 no-primary (secondary-only) and species- and clonality-matched isotype controls, plus CALHM1-knockout tissue if available as a biological negative (standard IHC practice). For chromogenic staining, block endogenous peroxidase and distinguish cortical pigment from specific signal; for IF, assess cortical autofluorescence with an unstained section (standard IHC/IF practice).
⚠️Feasibility: A target-specific fixation window and the effect of fixation are unreported in the supplied evidence; the selected A03599-1 rat-liver IHC caption also leaves the fixative unreported (caption: fixative not stated). Antigen-retrieval dependence is unreported, so assess retrieval on matched paraffin sections before scoring; the supplied evidence does not establish that frozen sections or IF are easier (application evidence: no matched comparison). In cerebral cortex, endogenous pigment and autofluorescence can complicate interpretation, particularly for IF (standard IHC/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 chromogenic IHC by checking retrieval, cellular distribution and controls before interpreting staining intensity.
How should I retrieve CALHM1 in paraffin sections when staining is weak?
Start with citrate buffer at pH 6.0, heated to 95–98 °C for 20 min (page retrieval setting). Allow sections to cool in the retrieval buffer, then compare staining in neuronal cells of cerebral cortex with a matched section processed without retrieval (HPA: medium neuronal staining; standard IHC practice). If signal remains weak, adjust heating within a controlled pilot while keeping antibody concentration and chromogen development constant (standard IHC practice). Judge improvement by clearer cellular staining without increased staining in a negative comparison tissue such as adipocytes in adipose tissue (HPA: adipocytes not detected).
Could fixation explain variable CALHM1 staining across paraffin sections?
Target-specific fixation sensitivity is unknown because the supplied CALHM1 tissue image states an antibody concentration of 5 µg/mL but does not report a fixative (caption: A03599-1). Record the fixative, fixation duration, tissue thickness and processing schedule for each specimen, and compare sections prepared under matched conditions (standard IHC practice). If staining differs, run a small fixation-time comparison using the same retrieval at pH 6.0 and the same detection settings (page retrieval setting; standard IHC practice). Interpret that comparison within the tested specimens; HPA staining patterns establish neither a fixation requirement nor a fixation-induced loss of CALHM1 (HPA: tissue IHC profile).
Should CALHM1 staining appear at the membrane or in the cytoplasm?
Evaluate membrane-associated staining alongside intracellular staining: CALHM1 is annotated at the cell membrane and endoplasmic reticulum membrane, with basolateral epithelial localisation reported by similarity (UniProt Q8IU99 subcellular). HPA reports cytoplasmic expression in subsets of neurons and adrenal gland cells, so cytoplasmic staining alone is not grounds to reject a neuronal result (HPA: tissue IHC profile). In cerebral cortex, identify neuronal cells before scoring intensity and compare with an adjacent negative-control section (HPA: medium staining in neuronal cells; standard IHC practice). Treat a diffuse deposit outside intact cells as suspect, and assess morphology and control staining before assigning it to CALHM1 (standard IHC practice).
How does epitope position affect CALHM1 IHC troubleshooting?
Check the antibody's stated immunogen or epitope before attributing weak staining to retrieval, because the supplied record does not identify the catalog antibody's binding region (catalog information supplied here). CALHM1 has 4 predicted transmembrane segments, extracellular loops at residues 38–49 and 126–180, and a cytoplasmic C-terminal region at 207–346 (UniProt Q8IU99 topology). The record lists a glycosylation site at residue 140 and no annotated isoforms, so do not assign an unexpected staining pattern to a particular isoform (UniProt Q8IU99 processing). Compare retrieval conditions with matched controls only after documenting the epitope, since processing can affect antibody access in paraffin sections (standard IHC practice).
How can IF help assess a questionable CALHM1 IHC pattern?
Use IF as a separate corroboration experiment and multiplex CALHM1 with a validated neuronal marker when checking cerebral cortex, where HPA reports staining in a subset of neuronal cells (HPA: tissue IHC profile; standard IF practice). Choose fluorophores in channels with low measured tissue autofluorescence, and include single-label and no-primary controls to distinguish bleed-through and background from cellular signal (standard IF practice). Select permeabilisation after confirming the antibody epitope: a cytoplasmic loop or C-terminal epitope requires intracellular access, whereas an extracellular-loop epitope may be assessed without it (UniProt Q8IU99 topology; standard IF practice). The 5 µg/mL tissue-IHC caption supplies no IF fixation, permeabilisation or antibody concentration condition (caption: A03599-1).
What should I check when CALHM1 DAB staining is widespread?
Run no-primary and detection-only sections to identify secondary-reagent deposits or endogenous enzyme activity before changing the CALHM1 antibody condition (standard IHC practice). For peroxidase-based DAB detection, include a peroxidase block, then check whether background follows tissue edges, folds or damaged areas rather than intact cells (standard IHC practice). Compare the suspect section with cerebral cortex neuronal cells and adipose-tissue adipocytes under matched staining conditions; HPA reports medium neuronal staining and no detectable adipocyte staining (HPA: tissue IHC profile). If background persists, optimise blocking, wash stringency and chromogen development one variable at a time while retaining the citrate pH 6.0 retrieval reference (standard IHC practice; page retrieval setting).
How should I quantify CALHM1 staining across tissue sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and compartment before scoring: HPA reports CALHM1 staining in a subset of cerebral cortex neuronal cells, while UniProt also annotates membrane and endoplasmic reticulum localisation (HPA: tissue IHC profile; UniProt Q8IU99 subcellular). For chromogenic sections, record the percentage of positive target cells and staining intensity, or calculate an H-score from intensity categories using the same thresholds throughout the study (standard IHC practice). Normalise positive-cell counts to all evaluable cells of the specified type, or report positive-cell density per mm² of viable tissue (standard IHC practice). Keep retrieval, antibody concentration, imaging and DAB development matched across groups, and exclude folds and necrotic regions before comparison (standard IHC practice).
When is a CALHM1-positive IHC pattern convincing rather than artefactual?
A convincing result has reproducible cellular staining in an expected population, such as a subset of cerebral cortex neuronal cells, with appropriate controls and preserved morphology (HPA: tissue IHC profile; standard IHC practice). Check whether membrane-associated or intracellular signal fits CALHM1's annotated cell-membrane and endoplasmic-reticulum locations; HPA also describes cytoplasmic staining in neuronal subsets (UniProt Q8IU99 subcellular; HPA: tissue IHC profile). Be cautious when intense staining is confined to section edges, necrotic areas or cells outside the defined population, especially if it appears in a no-primary control (standard IHC practice). Endogenous peroxidase can produce DAB signal, so verify the peroxidase block before assigning such deposits to CALHM1 (standard IHC practice).
Boster reagents
Best CALHM1 / Calcium homeostasis modulator protein 1 IHC Antibodies
A03599-1 has IHC data from rat liver tissue and IF data from rat liver cells (catalog: image captions); listed reactivity covers human, mouse, and rat (catalog: reactivity).
Real IHC data
Anti-CALHM1 Antibody
Cat # A03599-1
A03599-1 is the rendering SKU; its IHC image shows rat liver tissue at 5 μg/mL (IHC image caption). Its IF image shows rat liver cells at 20 μg/mL (IF image caption), and its listed applications include IHC-P and IF (catalog: applications).
Which to pick: For tissue IHC, choose A03599-1: IHC-P is listed (catalog: applications), and its own image shows rat liver tissue (IHC image caption); the fixative is unreported (IHC image caption). For IF/ICC, A03599-1 has IF data from rat liver cells (IF image caption), while ICC validation is unreported (catalog: applications). For cross-species work, A03599-1 lists human, mouse, and rat reactivity (catalog: reactivity); it has a rabbit host, but clonality is unspecified (catalog: host and clone).
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 Cytoplasmic in tissue; membrane and ER localisation annotated (HPA tissue IHC; 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: Subset staining can make whole-field scoring misleading (HPA tissue IHC); Isoform / epitope: No isoforms or cleavage annotated; epitope side depends on topology (UniProt); Regulation: Predominantly expressed in adult brain (UniProt). 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.