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CABS1 / Calcium-binding and spermatid-specific protein 1 · IHC design guide
Design Immunohistochemistry for CABS1
This guide focuses on cytoplasmic CABS1 staining in late spermatids in paraffin testis sections (HPA tissue IHC). Start the catalog antibody at 5 μg/mL (datasheet: 5 μg/mL) and score staining by cell type.
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 | Cytoplasm 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). Selected-image fixative and duration unreported (datasheet A15713); verify before use. | |
| Caveat | Signal depends on late spermatids in sampled tubules (HPA tissue IHC) | |
| Regulation | Enriched in late spermatids (HPA tissue IHC) | |
| Isoform / epitope | No annotated isoforms; one full-length chain (UniProt) |
Section 1
Recommended CABS1 IHC & IF Protocols
Compare the catalog antibody’s IHC-P protocol (datasheet) with published CABS1 staining methods for human 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 rule); compare high-pH retrieval for human sections (PMC11098423).
Section 2
What Is the Expected CABS1 Staining Pattern?
CABS1 should stain the cytoplasm of elongated or late spermatids in testis, with high staining reported in those cells (HPA: testis IHC). UniProt describes CABS1 as mostly cytoplasmic, with late mitochondrial association and flagellar localization reported by similarity; it has no transmembrane segment (UniProt Q96KC9). The tissue IHC pattern is rated Enhanced for consistency with RNA data, pending external verification (HPA: reliability).
| Strong cytoplasmic staining in elongated or late spermatids, with other structures remaining interpretable. | This matches the observed high testis signal and cytoplasmic profile (HPA: testis IHC). Assess cell identity and compartment together; intensity alone cannot establish that staining is CABS1-specific (general IHC practice). |
| Predominantly nuclear staining, or a crisp cell-surface outline instead of cytoplasmic staining. | These compartments do not match the reported tissue pattern (HPA: cytoplasmic expression in late spermatids). CABS1 has no annotated transmembrane segment (UniProt Q96KC9 topology). Treat the pattern as suspect and check controls and detection background (general IHC practice). |
| Strong staining in cells outside the late-spermatid population, especially across several tissue compartments. | The observed positive population is elongated or late spermatids (HPA: testis IHC). Broad staining raises concern for cross-reactivity or endogenous detection activity; use appropriate controls to distinguish them (general IHC practice). |
| A diffuse chromogenic haze covers cells and surrounding tissue, obscuring spermatid boundaries. | A haze that does not follow the reported late-spermatid cytoplasmic pattern cannot be scored confidently as CABS1 (HPA: testis IHC). Review blocking, antibody concentration, washing and detection controls (general IHC practice). |
| No signal in morphologically identifiable elongated or late spermatids in testis. | This conflicts with the reported high positive population (HPA: testis IHC). First confirm that the section contains the relevant cells; then evaluate staining reagents and the general IHC workflow with controls (general IHC practice). |
💡Expected CABS1 appearanceCall a positive result when elongated or late spermatids show high cytoplasmic staining (HPA: testis IHC); dominant nuclear or widespread unrelated-cell staining is suspect (HPA: cytoplasmic late-spermatid profile; general IHC practice).
| Cell population and tissue selection | Testis provides the reported high positive population: elongated or late spermatids (HPA: testis IHC). Adipocytes in adipose tissue are reported as not detected and can serve as a documented negative comparison (HPA: adipose tissue IHC). |
| Subcellular interpretation | The tissue IHC observation is cytoplasmic (HPA: testis IHC). Mitochondrial inner-membrane association occurs during late differentiation, while principal-piece flagellar localization is reported by similarity (UniProt Q96KC9); neither is an established separate chromogenic IHC readout here. |
| Antibody evidence | Two rabbit polyclonal antibodies, HPA044016 and HPA055352, have Enhanced IHC status (HPA: antibody validation). The tissue profile shows high consistency with RNA expression but awaits external verification (HPA: reliability); controls remain useful for an individual run (general IHC practice). |
| Can IF/ICC show the same localization? | No HPA ICC-IF images or main subcellular location are available for CABS1 (HPA: subcellular record). The IHC cytoplasmic pattern can guide interpretation, but it does not validate an IF/ICC staining pattern (HPA: tissue IHC and subcellular records). |
| Situation | Likely cause | Next action |
|---|---|---|
| Testis section is blank where late spermatids should be visible. | The section may lack identifiable positive cells, or the staining run may have failed (HPA: high staining in elongated or late spermatids; general IHC practice). | Verify the cell population morphologically and review the run controls, primary-antibody step and detection reagents (general IHC practice). |
| Signal appears in nearly every testis cell. | This exceeds the reported late-spermatid cytoplasmic profile and may reflect nonspecific antibody binding or endogenous detection activity (HPA: testis IHC; general IHC practice). | Compare a negative control and review blocking, antibody concentration and detection controls before assigning positivity (general IHC practice). |
| Nuclear staining dominates the putative positive cells. | The compartment disagrees with the observed cytoplasmic profile (HPA: testis IHC). | Check the counterstain and a negative control, then score only a reproducible cytoplasmic signal in the expected cells (general IHC practice; HPA: testis IHC). |
| Diffuse background makes individual cells hard to score. | Nonlocalized signal prevents assessment of the reported cell-specific pattern (HPA: testis IHC; general IHC practice). | Review antibody concentration, blocking, washing and chromogen development using the run controls (general IHC practice). |
| Flagella are not distinctly stained, but late-spermatid cytoplasm is positive. | The high cytoplasmic tissue signal is observed by IHC, whereas flagellar localization is reported by similarity in UniProt (HPA: testis IHC; UniProt Q96KC9). | Judge this IHC result against the documented cytoplasmic late-spermatid pattern; do not require visible flagellar staining for a positive call (HPA: testis IHC). |
| An IF/ICC image suggests a sharply defined organelle pattern. | HPA supplies no ICC-IF images or main subcellular location to confirm that pattern (HPA: subcellular record). | Describe the IF/ICC observation as unvalidated by these sources; use the documented tissue IHC pattern only as context (HPA: tissue IHC and subcellular records). |
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 look for staining in elongated or late spermatids (HPA: High in elongated or late spermatids). Use adipose tissue as a negative tissue (HPA: Not detected in adipocytes); on the testis slide, assess cells outside the elongated or late spermatid compartment as internal background controls, without assuming they are confirmed negative (HPA: High in 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; an isotype control matched to the primary antibody’s host species, immunoglobulin class and clonality; and, where available, CABS1 knockout tissue or a cognate peptide-block control (standard IHC/IF practice). On testis sections, block endogenous peroxidase for chromogenic detection, account for endogenous biotin if using biotin-based detection, and check autofluorescence if using IF (standard IHC/IF practice).
⚠️Feasibility: A target-specific fixation window and the effect of antigen retrieval are unreported in the supplied CABS1 evidence; the selected A15713 tissue-IHC caption also leaves the fixative unreported (selected-SKU caption: fixative not stated). The supplied evidence does not establish whether frozen sections or IF/ICC are easier than paraffin IHC (HPA subcellular: no cell lines with ICC-IF images). Check testis sections for background in adjacent germ cells and, for IF, native autofluorescence before interpreting spermatid staining (standard IHC/IF 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
Use late spermatids as the reference population when assessing CABS1 staining in paraffin sections (HPA tissue IHC).
How should I retrieve CABS1 antigen when chromogenic staining is weak?
Start with citrate pH 6.0 heat-induced retrieval at 95–98 °C for 20 min (page retrieval setting: cytoplasmic / membrane antigen). Allow sections to cool in retrieval buffer before washing, and keep heating conditions consistent across slides (standard IHC practice). Compare retrieved sections with a testis control containing late spermatids, the expected positive population (HPA tissue IHC). If staining remains weak, optimise antibody concentration and detection exposure using matched sections before interpreting an alternative retrieval condition (standard IHC practice). Record any retrieval change alongside staining intensity, because comparisons require consistent processing (standard IHC practice).
Could fixation explain absent CABS1 staining in my paraffin sections?
CABS1-specific fixation sensitivity is unknown from the supplied evidence, so an absent signal cannot be assigned to fixation alone (supplied fixation evidence). Record the fixative, fixation duration and processing history for every section, then compare specimens processed together (standard IHC practice). Use a testis section with late spermatids as a positive control for the staining run (HPA tissue IHC). If control staining is also absent, check section integrity, retrieval, antibody incubation and detection before drawing a biological conclusion (standard IHC practice). The selected tissue-IHC caption does not state a fixative and names CLPH, so it cannot establish CABS1 fixation performance (selected caption: A15713).
Which CABS1 staining pattern should I expect in testis?
Prioritise cytoplasmic staining in elongated or late spermatids when evaluating testis sections (HPA tissue IHC: high in late spermatids). CABS1 is described as mostly cytoplasmic, with associations to the acrosome, mitochondrial inner membrane during late differentiation, and sperm flagellar principal piece (UniProt Q96KC9: subcellular location, partly by similarity). These annotations support examining cell bodies and identifiable spermatid structures separately, without requiring every structure to stain in one section (UniProt Q96KC9; standard IHC interpretation). CABS1 has no annotated transmembrane segment, so a uniform cell-surface rim is not its expected defining pattern (UniProt Q96KC9: topology). Compare each compartment with its morphology and a matched negative control (standard IHC practice).
How do unknown epitopes and CABS1 modifications affect interpretation?
The supplied record lists 0 isoforms and a single 1–395 chain, but it does not identify this antibody’s epitope (UniProt Q96KC9; supplied antibody evidence). It also lists phosphorylated residues, including serines at 273, 319 and 376, without establishing an effect on IHC binding (UniProt Q96KC9: modified residues). Do not attribute variable staining to an isoform or phosphorylation state without epitope information and direct validation (standard IHC interpretation). Compare serial sections processed identically, and use an independently validated antibody if an epitope-dependent explanation needs testing (standard IHC practice). Report the antibody identity and retrieval conditions with any compartment-specific claim (standard IHC practice).
How can IF help assess CABS1 localisation alongside a spermatid marker?
Pair CABS1 with a validated marker that identifies elongated or late spermatids, the expected positive population (HPA tissue IHC; standard multiplex IF practice). Place the weaker signal in a spectrally separated far-red channel where tissue autofluorescence is lower in the specimen, and check single-label controls for bleed-through (standard IF practice). Because CABS1 is mostly cytoplasmic and has no transmembrane segment, assess permeabilisation for access to intracellular epitopes rather than assuming surface accessibility (UniProt Q96KC9: location and topology). Keep any mitochondrial inner-membrane interpretation cautious because that association is reported for late differentiation and epitope access is unknown (UniProt Q96KC9: subcellular location). No CABS1 ICC/IF images are supplied here to validate an IF pattern (HPA subcellular payload).
What should I check when chromogenic CABS1 staining appears diffuse?
Examine a no-primary control and the expected late-spermatid distribution before calling diffuse colour CABS1-positive (standard IHC practice; HPA tissue IHC). Block endogenous peroxidase when using an HRP/DAB detection workflow, then compare background with a matched control section (standard chromogenic IHC practice). Check whether excessive primary concentration, incomplete washing or prolonged DAB development raises staining across unrelated cell populations (standard IHC practice). Adipocytes and adrenal glandular cells are reported as not detected and can inform tissue-level comparisons when comparably processed material is available (HPA tissue IHC). The selected A15713 caption names CLPH, so its stated 5 µg/mL cannot be treated as a validated CABS1 concentration (selected caption: A15713).
How should I score CABS1 staining across testis sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define elongated or late spermatids by morphology before scoring their cytoplasmic signal (HPA tissue IHC; standard IHC practice). Report the percentage of positive cells and an H-score combining that percentage with intensity, using the same thresholds across slides (standard IHC scoring practice). If measuring stained profiles per mm², specify whether the denominator is total section area or evaluable seminiferous-tubule area (standard image-analysis practice). Normalise cell-based comparisons to the number of evaluable late spermatids, because their abundance can differ between sampled areas (standard IHC quantification practice). Exclude damaged tissue and keep retrieval, imaging and colour-deconvolution settings consistent across the comparison (standard IHC practice).
How can I distinguish genuine CABS1 signal from staining artefact?
A convincing positive pattern concentrates in the cytoplasm of elongated or late spermatids in testis (HPA tissue IHC). Flag strong nuclear-only signal, a uniform cell-surface rim or staining dominated by unrelated cells for review against morphology and controls (UniProt Q96KC9: location and topology; standard IHC interpretation). Inspect section edges and damaged or necrotic areas separately, since their colour deposits may reflect processing artefact (standard IHC practice). Compare no-primary and peroxidase-block controls when diffuse DAB signal suggests detection background or endogenous enzyme activity (standard chromogenic IHC practice). HPA rates the tissue pattern Enhanced while external verification remains pending, so independent confirmation strengthens a new localisation claim (HPA tissue IHC: reliability).
Boster reagents
Best CABS1 / Calcium-binding and spermatid-specific protein 1 IHC Antibodies
A15713 has real IHC data from human testis at 5 μg/mL (image caption). Human and rat reactivity are listed (catalog); no IF data are supplied (catalog).
Real IHC data
Anti-CLPH CABS1 Antibody
Cat # A15713
A15713 is the only SKU shown, with an IHC image from human testis at 5 μg/mL (image caption). It lists IHC-P and human and rat reactivity (catalog); no IF image is supplied (catalog).
Which to pick: For paraffin-section IHC, choose A15713: IHC-P is listed (catalog), and its human testis image used 5 μg/mL (image caption); the fixative is unreported (image caption). For IF/ICC, A15713 has no listed IF/ICC application or IF image, and its clonality is unreported (catalog). For cross-species studies, A15713 lists human and rat reactivity (catalog), but its pictured IHC result is from human testis only (image caption).
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 Cytoplasm 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). Selected-image fixative and duration unreported (datasheet A15713); verify before use.; Caveat: Signal depends on late spermatids in sampled tubules (HPA tissue IHC); Isoform / epitope: No annotated isoforms; one full-length chain (UniProt); Regulation: Enriched in late spermatids (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.