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CABS1 / Calcium-binding and spermatid-specific protein 1 · IHC design guide
Design Immunohistochemistry for CABS1
Use human testis as a positive control for CABS1 IHC-P; late spermatids show cytoplasmic staining (HPA tissue IHC). Start the IHC-validated antibody at 5 μg/mL (datasheet: A15713) and compare staining with a negative control (standard IHC practice).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CABS1 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 late spermatids (HPA tissue IHC) | |
| Staining pattern | Late spermatids show cytoplasmic staining (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen) | |
| Positive control | Testis | |
| 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 | Signal depends on late spermatids being present in the section (HPA tissue IHC) | |
| Regulation | Testis-enriched expression (HPA tissue IHC) | |
| Isoform / epitope | No annotated isoforms; one chain spans residues 1–395 (UniProt) |
Section 1
Recommended CABS1 IHC & IF Protocols
The catalog antibody’s IHC-P protocol is accompanied by published paraffin-section methods for human submandibular gland and testis (PMC11098423) and mouse testis (PMC7827751).
| Sample | Tissue sections; selected-image fixative not specified (standard IHC workflow) |
| Fixation | Image fixative and duration unreported (datasheet A15713); 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-CABS1, 5 μg/mL (datasheet A15713) |
| 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 | CABS1-positive staining in elongated or late spermatids of testis (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic expression in late spermatids. No signal in the no-primary control. |
💡Decision noteStart with citrate pH 6.0 retrieval at 95–98 °C for 20 min (page antigen retrieval); the human immunoperoxidase method used high-pH retrieval (PMC11098423).
Section 2
What Is the Expected CABS1 Staining Pattern?
For paraffin-section IHC, expect CABS1 staining in the cytoplasm of elongated or late spermatids in testis (HPA: High in elongated or late spermatids; cytoplasmic profile). UniProt also places CABS1 at the acrosome and, by similarity, the sperm flagellum, while describing it as mostly cytoplasmic and lacking a transmembrane segment (UniProt Q96KC9). HPA rates the tissue IHC pattern Enhanced, with external verification pending (HPA: reliability description).
| Strong cytoplasmic chromogen in elongated or late spermatids, concentrated in the expected cells. | This matches the reported testis pattern; assess intensity within those cells, since the expected positive population is specific (HPA: High in elongated or late spermatids; cytoplasmic profile). |
| Signal appears only in nuclei, with no convincing spermatid cytoplasm. | A nuclear-only pattern conflicts with the reported cytoplasmic IHC profile and UniProt locations; review morphology and controls before scoring it as CABS1 (HPA: cytoplasmic profile; UniProt Q96KC9: subcellular locations). |
| Strong staining appears mainly in cell types other than elongated or late spermatids. | That distribution differs from the reported testis positive population. Consider cross-reactivity or endogenous detection activity as possible IHC causes, then compare with a negative-control section (HPA: testis IHC; general IHC practice). |
| Chromogen covers much of the section without clear cellular boundaries. | Diffuse background cannot establish the cell-restricted cytoplasmic pattern; check whether control sections show similar deposit before interpreting the slide (HPA: cytoplasmic expression in late spermatids; general IHC practice). |
| No spermatid signal is visible in a testis section containing identifiable late spermatids. | This fails the expected positive-tissue check. Verify that the relevant cells are present, then review the IHC detection run; absence alone does not establish absent CABS1 expression (HPA: High in elongated or late spermatids; general IHC practice). |
💡Expected CABS1 appearanceCall a result positive when elongated or late spermatids show High, predominantly cytoplasmic staining; nuclear-only, diffuse, or chiefly other-cell staining needs control review (HPA: testis IHC and cytoplasmic profile; UniProt Q96KC9: mostly cytoplasmic).
| Positive tissue and scoring population | Testis is RNA tissue-enriched, and the reported IHC positive cells are elongated or late spermatids; score those cells rather than averaging the whole section (HPA: RNA specificity and testis IHC). |
| Cellular location | CABS1 is mostly cytoplasmic; UniProt also lists acrosome, mitochondrial inner membrane during late differentiation, and flagellum by similarity. These annotations provide context, while the observed HPA tissue IHC profile is cytoplasmic (UniProt Q96KC9; HPA: tissue profile). |
| Strength of IHC evidence | HPA rates tissue IHC reliability Enhanced, citing consistency with RNA and pending external verification; both listed rabbit polyclonal antibodies have Enhanced IHC status (HPA: reliability description; antibodies HPA044016 and HPA055352). |
| IF/ICC Q&A: Is there a verified cellular IF pattern here? | No: HPA supplies no ICC-IF main location or cell-line images for CABS1. Use the tissue IHC result to guide interpretation of paraffin sections, without treating it as IF/ICC validation (HPA: subcellular ICC-IF; tissue IHC). |
| Situation | Likely cause | Next action |
|---|---|---|
| Late spermatids are present, but the positive tissue has no detectable chromogen. | The observed result disagrees with HPA’s High spermatid staining; a run-level detection issue is one possible explanation (HPA: testis IHC; general IHC practice). | Confirm cell identification on the counterstain and inspect positive and detection-control sections before changing interpretation (HPA: positive cell type; general IHC practice). |
| Only nuclei stain in testis. | Nuclear-only signal does not match the reported cytoplasmic tissue profile or UniProt locations (HPA: cytoplasmic profile; UniProt Q96KC9: subcellular locations). | Compare serial-section morphology and controls; report the nuclear pattern as discordant until its source is resolved (HPA: cytoplasmic profile; general IHC practice). |
| Other testis cells stain more strongly than late spermatids. | The dominant positive population differs from the HPA result; nonspecific antibody binding or endogenous detection activity may contribute (HPA: testis IHC; general IHC practice). | Check a matched negative-control section and verify the detection reagents before assigning CABS1 positivity to those cells (HPA: positive cell type; general IHC practice). |
| The section has widespread, poorly bounded chromogen. | Background deposit can obscure the expected cell-restricted pattern (HPA: cytoplasmic late-spermatid profile; general IHC practice). | Compare the background with a negative-control section; review blocking, washes, and chromogen development as general IHC workflow checks (general IHC practice). |
| A cell population listed as undetected by HPA appears positive. | For example, HPA reports no detection in adipose-tissue adipocytes; a positive result there conflicts with that reference observation, but does not identify the cause (HPA: adipose-tissue IHC). | Review tissue and cell identification, compare controls, and describe the discordance rather than treating the HPA negative as an absolute exclusion (HPA: adipose-tissue IHC; general IHC practice). |
| An IF/ICC image is being used to confirm the paraffin-section result. | HPA provides neither an ICC-IF main location nor cell-line images for CABS1, so this payload cannot establish an IF/ICC reference pattern (HPA: subcellular ICC-IF). | Keep the IHC call tied to testis cell identity and cytoplasmic chromogen; seek IF/ICC validation on its own guide page (HPA: tissue IHC and subcellular ICC-IF). |
Experiment evidence
IHC & IF images showing CABS1 staining
A15713 · IHCImmunohistochemistry of CLPH in human testis tissue with CLPH antibody at 5 μg/mL.
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000145309-CABS1/tissue/cerebral+cortex#imid_20086461
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000145309-CABS1/tissue/colon#imid_20086379
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000145309-CABS1/tissue/liver#imid_20086396
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000145309-CABS1/tissue/kidney#imid_20086389
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CABS1 IHC & IF
🧪Run testis first and expect staining in elongated or late spermatids (HPA: High). Use adipose tissue as a negative comparator (HPA: adipocytes Not detected); on the testis slide, assess other cell populations for staining above background rather than assuming they are negative (HPA: positive call is specific to elongated or late spermatids).
Positive control tissue: Testis (Elongated or late spermatids, HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA carries no ICC-IF cell line for CABS1; derive a cell-line control from the positive tissue's cell type (Elongated or late spermatids) and confirm it by RNA or western blot first.
Technical controls: Include a no-primary, secondary-only control and an isotype control matched to the primary antibody’s host species and clonality; use CABS1 knockout tissue if available, or peptide competition if the immunizing peptide is known (standard IHC control practice). For chromogenic testis IHC, block endogenous peroxidase and check background in the no-primary control (standard IHC practice).
⚠️Feasibility: The selected A15713 testis caption names CLPH and does not report a fixative, so it does not establish CABS1 specimen processing (caption: CLPH; fixative not stated). A CABS1-specific fixation window and retrieval dependence are unreported in the supplied evidence; optimize retrieval against the testis positive and adipose negative controls (HPA: testis High; adipose adipocytes Not detected). There is no supplied basis to call frozen sections or IF easier, and testis background staining should be assessed with the technical controls (HPA: no ICC-IF images; standard IHC control practice).
HPA tissue IHC evidence for CABS1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — High 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 |
|---|---|---|---|---|
| Testis | Elongated or late spermatids | 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 → |
| Appendix | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | Not detected | Protein (IHC) | HPA → |
| Breast | Adipocytes | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced CABS1 IHC Tips
Troubleshoot CABS1 staining in chromogenic IHC of paraffin sections, using late spermatids as the main biological reference (HPA: tissue IHC).
How should I retrieve CABS1 when paraffin sections stain weakly?
Use citrate pH 6.0 heat-induced retrieval at 95–98 °C for 20 min before staining CABS1 paraffin sections (page retrieval setting). Let sections cool in retrieval buffer, then compare the IHC-validated antibody with a no-primary control on the same run (standard IHC practice). If late-spermatid staining remains weak, test a more alkaline retrieval buffer only as a fallback, keeping detection conditions constant (standard IHC practice; HPA: high expression in elongated or late spermatids). Excessive retrieval can damage tissue morphology and make compartment-level interpretation unreliable (standard IHC practice). Record buffer, temperature, time, and staining pattern for each trial (standard IHC practice).
Could fixation explain weak or uneven CABS1 staining?
CABS1-specific sensitivity to fixation is unknown: the supplied evidence contains no target-specific fixation comparison (provided evidence). For paraffin IHC, document fixative, fixation duration, section thickness, and storage conditions before changing antibody or retrieval conditions (standard IHC practice). Compare similarly processed testis sections in one staining run, because variable processing can change staining intensity and tissue preservation (standard IHC practice; HPA: testis tissue enriched). Judge recovery by late-spermatid staining alongside intact morphology and low no-primary background (HPA: cytoplasmic expression in late spermatids; standard IHC practice). Do not treat the reported tissue pattern or protein topology as evidence of a particular fixation effect (HPA: tissue IHC; UniProt Q96KC9: no transmembrane segment).
Which CABS1 staining pattern should count as plausible in testis?
Prioritise cytoplasmic signal in elongated or late spermatids when reviewing chromogenic testis sections (HPA: high expression in elongated or late spermatids; cytoplasmic expression in late spermatids). CABS1 is mostly cytoplasmic, with reported association with the mitochondrial inner membrane during late differentiation and localisation to the sperm flagellar principal piece by similarity (UniProt Q96KC9: subcellular location). Acrosomal localisation is also annotated, so evaluate discrete signal in relation to spermatid morphology (UniProt Q96KC9: acrosome; standard IHC practice). Check counterstained nuclei and adjacent structures before calling a tiny DAB deposit compartment-specific (standard IHC practice). Diffuse staining across unrelated cell populations deserves control-based review (HPA: tissue IHC; standard IHC practice).
How do I investigate a suspected epitope or isoform problem?
Do not assign unexpected staining to a named CABS1 isoform: none is listed in the supplied record (UniProt Q96KC9: 0 annotated isoforms). The record describes one 1–395 chain and no transmembrane segment, but supplies no antibody epitope map (UniProt Q96KC9: processing and topology; provided evidence). Ask whether the IHC-validated antibody's documented immunogen overlaps the region being assessed before interpreting a negative result (standard antibody-validation practice). CABS1 has annotated phosphosites at residues 273, 287, 319, and 376; their effect on this antibody's staining is untested here (UniProt Q96KC9: modified residues; provided evidence). Compare retrieval conditions and a positive testis control before proposing epitope masking (standard IHC practice; HPA: testis tissue enriched).
How can I check CABS1 localisation by multiplex immunofluorescence?
Pair CABS1 with a validated late-spermatid marker and inspect whether the signals occupy the expected cells (HPA: cytoplasmic expression in late spermatids; standard IF practice). Choose spectrally separated fluorophores, favouring a far-red channel when tissue autofluorescence obscures shorter wavelengths, and include single-stain controls (standard IF practice). For a cytoplasmic epitope, start with mild permeabilisation; assessing an inner-mitochondrial-membrane-facing epitope may require a separately validated access condition (UniProt Q96KC9: cytoplasm and mitochondrial inner membrane; standard IF practice). Avoid assuming that membrane association identifies the antibody epitope's side, because its orientation is not supplied (provided evidence). No CABS1 ICC/IF images are listed in the supplied HPA record, so validate specificity independently (HPA: subcellular record).
What should I change when DAB obscures spermatid staining?
First compare testis sections stained with and without primary antibody to identify detection-system background (standard IHC practice; HPA: high expression in elongated or late spermatids). Apply a peroxidase block before chromogenic detection, then assess whether DAB still appears in both sections (standard chromogenic IHC practice). Optimise blocking, washing, antibody concentration, and DAB development one variable at a time while preserving late-spermatid morphology (standard IHC practice; HPA: cytoplasmic expression in late spermatids). Use a tissue reported as undetected, such as adipose tissue, as a contextual negative control when available (HPA: adipocytes not detected). Widespread staining outside the expected cells warrants further specificity checks (HPA: tissue IHC; standard IHC practice).
How should I score CABS1 staining across testis sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define elongated or late spermatids as the scoring population before reviewing intensity (HPA: high expression in elongated or late spermatids). Report their % positive cells and an H-score using intensity grades 0–3, with thresholds held constant across sections (standard IHC scoring practice). Normalise positive counts to the number of evaluable late spermatids; if reporting density, specify positive cells per mm² of assessed testis area (standard IHC quantification practice). Sample comparable tissue regions and exclude folds, detached material, and poorly preserved areas using predefined criteria (standard IHC practice). Keep background estimates from no-primary controls separate from biological scores (standard IHC practice).
How can I distinguish true CABS1 signal from artefact?
A convincing result places cytoplasmic signal in elongated or late spermatids and agrees with testis-enriched expression (HPA: tissue IHC and RNA specificity). Flag dominant nuclear staining or broad staining of unrelated cells for review against morphology and controls (HPA: cytoplasmic expression in late spermatids; standard IHC practice). Edge-only colour, necrotic regions, and signal retained without primary antibody suggest processing or endogenous-enzyme artefact (standard chromogenic IHC practice). Compare suspected signal with a peroxidase-blocked, no-primary section before interpreting DAB deposits (standard IHC practice). The supplied A15713 tissue caption names CLPH, so that caption alone does not establish CABS1 antibody performance (supplied A15713 caption).
Boster reagents
Best CABS1 / Calcium-binding and spermatid-specific protein 1 IHC Antibodies
A15713 has human testis IHC data at 5 μg/mL (catalog IHC image caption). Human and rat reactivity is listed (catalog reactivity); no IF image is supplied (catalog IF image alts).
Real IHC data
Anti-CLPH CABS1 Antibody
Cat # A15713
A15713 lists IHC-P and has an IHC image of human testis stained at 5 μg/mL (catalog applications; catalog IHC image caption). Its listed reactivity is human and rat, while the supplied IHC validation specifies human samples (catalog reactivity; datasheet validation statement).
Which to pick: For paraffin-section IHC, choose A15713: it lists IHC-P, and its own caption documents human testis staining at 5 μg/mL; the fixative is unreported (catalog applications; catalog IHC image caption). No SKU has a listed IF/ICC application or IF image (catalog applications; catalog IF image alts). For cross-species work, A15713 lists human and rat reactivity, but its supplied IHC validation is human only; it is a rabbit antibody with no clone specified (catalog reactivity; datasheet validation statement; catalog host; catalog clone).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry Q96KC9 (CABS1_HUMAN, Calcium-binding and spermatid-specific protein 1).
- Human Protein Atlas. CABS1 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. CABS1 subcellular location (ICC-IF): Highest expression in Rh30: 0.0 nTPM.
- Human Protein Atlas. CABS1 antibody validation summary (2 antibodies).
- Identification and characterization of calcium binding protein, spermatid-associated 1 (CABS1)# in selected human tissues and fluids. PloS one 2024 — PMC11098423.
- Cabs1 Maintains Structural Integrity of Mouse Sperm Flagella during Epididymal Transit of Sperm. International journal of molecular sciences 2021 — PMC7827751.
- PubMed PMID:14702039 — UniProt-cited evidence.
- PubMed PMID:15815621 — UniProt-cited evidence.
- PubMed PMID:15489334 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CABS1 (Calcium-binding and spermatid-specific protein 1). Expected localisation Cytoplasmic in late spermatids (HPA tissue IHC). Antigen retrieval: Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen). Validated IHC antibody: A15713 at 5 μg/mL (the product's own IHC validation image is shown). Controls (HPA): positive Testis (Elongated or late spermatids); 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 A15713); 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-CABS1, 5 μg/mL (datasheet A15713); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: Keep fixation consistent across sections. (standard IHC practice; not target-specific); Caveat: Signal depends on late spermatids being present in the section (HPA tissue IHC); Isoform / epitope: No annotated isoforms; one chain spans residues 1–395 (UniProt); Regulation: Testis-enriched expression (HPA tissue IHC). Evidence: UniProt Q96KC9, HPA tissue IHC · Enhanced, HPA cell-line RNA · Highest expression in Rh30: 0.0 nTPM, Datasheet A15713, PMC11098423, PMC7827751. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CABS1/immunohistochemistry-ihc-guide.