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MSI1 / RNA-binding protein Musashi homolog 1 · IHC design guide
Design Immunohistochemistry for MSI1
Plan MSI1 chromogenic IHC in paraffin sections around cytoplasmic and nuclear tissue staining (HPA tissue IHC). This guide uses reported CNS and retinal staining for control selection (HPA tissue IHC) and the catalog antibody’s 0.5–1 μg/mL IHC-P range (datasheet A05052-1).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
MSI1 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 and nuclear tissue staining (HPA tissue IHC) | |
| Staining pattern | CNS glia and retinal ganglion cells; cytoplasmic/nuclear signal (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6 HIER, heat-mediated (datasheet A05052-1) | |
| Positive control | Caudate+4 more · see all | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation consistent across paraffin sections (standard IHC practice; not target-specific) | |
| Caveat | Antibody staining and RNA have medium consistency (HPA tissue IHC) | |
| Regulation | Fetal and adult tissue expression differs (UniProt) | |
| Isoform / epitope | No annotated isoforms; one 1–362 chain (UniProt) |
Section 1
Recommended MSI1 IHC & IF Protocols
The catalog antibody protocol uses citrate pH 6 retrieval (datasheet: A05052-1). The published IHC protocols below cover osteoarticular tissue, mouse brain, and cervical carcinoma tissue (PMC4433648; PMC11301063; PMC4279416).
| Sample | Paraffin-embedded human lung cancer tissues; fixative not specified (datasheet A05052-1) |
| Fixation | Image fixative and duration unreported (datasheet A05052-1); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat retrieval: Citrate pH 6, 20 min (datasheet A05052-1) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A05052-1) |
| Primary antibody | Rabbit anti-MSI1, 0.5-1μg/ml (datasheet A05052-1) |
| Primary incubation | Overnight at 4 °C (datasheet A05052-1) |
| Detection | Streptavidin-biotin complex (SABC), DAB chromogen (datasheet A05052-1) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | MSI1-positive staining in glial cells of caudate (HPA tissue IHC: Medium). HPA tissue profile: Cytoplasmic and nuclear expression in several tissues, including CNS and retina. No signal in the no-primary control. |
💡Decision noteStart with citrate pH 6 heat retrieval for paraffin sections (datasheet: A05052-1); the osteoarticular study used EDTA pH 8 (PMC4433648).
Section 2
What Is the Expected MSI1 Staining Pattern?
MSI1 should appear in cytoplasm and nuclei, including CNS glial cells, retinal ganglion cells, intestinal glandular cells, and pancreatic exocrine glandular cells (HPA: tissue IHC). It has no transmembrane segment, so an exclusively membrane-bound pattern is unexpected (UniProt O43347 topology). HPA rates tissue IHC reliability as Enhanced, while noting medium consistency between antibody staining and RNA expression (HPA: tissue IHC).
| Cytoplasmic and nuclear staining in caudate, cerebral cortex, or hippocampal glial cells. | This fits the reported MSI1 compartments and cell types; HPA records medium staining in these cells (HPA: tissue IHC). Score the relevant cells and compartments, since staining elsewhere in a section does not establish that its glial cells are positive (general IHC practice). |
| An exclusively sharp plasma-membrane outline, with no cytoplasmic or nuclear signal. | Treat this as an unexpected pattern and investigate an artefact or nonspecific reaction: MSI1 has no transmembrane segment (UniProt O43347 topology), and HPA describes cytoplasmic and nuclear tissue staining (HPA: tissue IHC). Compartment alone cannot identify the cause (general IHC practice). |
| Strong staining confined to a cell type reported as undetected, such as adipocytes in adipose tissue. | HPA reports MSI1 as not detected in these adipocytes (HPA: tissue IHC). Check for antibody cross-reactivity or endogenous chromogenic activity before calling the result positive (general IHC practice). An unexpected positive is a reason to investigate, not proof of either cause. |
| Broad, nearly uniform chromogen across cells and extracellular areas. | The distribution does not match HPA's cell-resolved cytoplasmic and nuclear MSI1 pattern (HPA: tissue IHC). Assess reagent background and endogenous detection activity with appropriate controls; diffuse deposit can obscure genuine stained cells (general IHC practice). |
| No staining in retinal ganglion cells or pancreatic exocrine glandular cells. | Both are reported at medium staining intensity (HPA: tissue IHC). Check slide quality and detection with a positive control before interpreting the negative; HPA's Enhanced rating does not guarantee that every preparation will yield a visible signal (HPA: tissue IHC; general IHC practice). |
💡Expected MSI1 appearanceCall an IHC result consistent with MSI1 when identifiable CNS glial, retinal ganglion, intestinal glandular, or pancreatic exocrine glandular cells show cytoplasmic and/or nuclear staining around the reported medium level (HPA: tissue IHC); isolated membrane outlines or uniform deposit warrant investigation (UniProt O43347 topology; general IHC practice).
| Which tissue and cell type is being scored? | HPA reports medium staining in retinal ganglion cells, CNS glial cells, small-intestinal and duodenal glandular cells, and pancreatic exocrine glandular cells; colon, rectum, and appendix glandular cells are Low (HPA: tissue IHC). A tissue name alone does not specify which cells should stain. |
| How much confidence does the tissue atlas provide? | HPA labels MSI1 tissue IHC Enhanced but describes only medium consistency between antibody staining and RNA expression (HPA: tissue IHC). Two listed rabbit polyclonal antibodies, HPA074923 and HPA075573, each have Enhanced IHC validation (HPA: antibodies). Interpret an individual slide alongside its controls. |
| Does protein architecture predict a surface stain or a shed fragment? | MSI1 has no transmembrane segment, signal peptide, propeptide, or annotated processed fragment; its listed chain spans residues 1–362 (UniProt O43347 topology and processing). These annotations support intracellular interpretation but cannot establish how a particular antibody performs in paraffin sections. |
| What pattern should IF/ICC show? | HPA reports approved nucleoplasm and cytosol localization in ICC-IF and lists AF22, SH-SY5Y, U2OS, and HAP1 image sets (HPA: subcellular; HPA: antibodies). Use this as a compartment comparison only; tissue IHC intensity and cell-type calls come from the HPA tissue record. |
| Situation | Likely cause | Next action |
|---|---|---|
| Expected CNS glial or retinal ganglion staining is absent. | The expected cell population may be absent from the viewed field, or the staining run may have failed; HPA reports medium signal in these cells (HPA: tissue IHC; general IHC practice). | Confirm cell identity and section quality, then review the run's positive control and the catalog antibody's IHC-P instructions before calling MSI1 negative (general IHC practice). |
| Colon, rectum, or appendix looks weaker than retina. | HPA calls glandular-cell staining Low in these intestinal sites but medium in retinal ganglion cells (HPA: tissue IHC). | Score each stated cell population against its own expected level; retain a suitable positive control to assess whether weak staining remains detectable (HPA: tissue IHC; general IHC practice). |
| Atypical cells stain while the expected cells do not. | Cell misidentification, cross-reactivity, or endogenous chromogenic activity are possible explanations; the HPA pattern is cell specific (HPA: tissue IHC; general IHC practice). | Recheck morphology and control slides, including a reagent control for detection background, before assigning the atypical signal to MSI1 (general IHC practice). |
| Chromogen is widespread or obscures cell boundaries. | Excess detection background or endogenous enzyme activity can create diffuse signal in chromogenic IHC (general IHC practice). | Inspect the reagent control and review blocking, washes, and detection settings in the validated IHC-P workflow; assess MSI1 only where cell boundaries and compartments remain readable (general IHC practice). |
| Staining appears only at the plasma membrane. | That pattern conflicts with the intracellular HPA tissue profile and MSI1's lack of a transmembrane segment (HPA: tissue IHC; UniProt O43347 topology). | Check a known-positive tissue for cytoplasmic or nuclear staining and review control slides for edge or detection artefacts before accepting the membrane signal (HPA: tissue IHC; general IHC practice). |
| A specimen reported as undetected shows a faint signal. | HPA lists adipose adipocytes and bronchial respiratory epithelial cells as Not detected; faint colour alone cannot identify its source (HPA: tissue IHC). | Compare the same cell type with the reagent control and an HPA-reported positive tissue, and record the discrepancy rather than treating faint colour as confirmed MSI1 expression (HPA: tissue IHC; general IHC practice). |
Experiment evidence
IHC & IF images showing MSI1 staining
A05052-1 · IHCIHC analysis of Musashi 1/Msi1 using anti-Musashi 1/Msi1 antibody (A05052-1). Musashi 1/Msi1 was detected in paraffin-embedded section of hu
A05052-1 · IHCIHC analysis of Musashi 1/Msi1 using anti-Musashi 1/Msi1 antibody (A05052-1). Musashi 1/Msi1 was detected in paraffin-embedded section of mo
A05052-1 · IFIF analysis of Musashi 1/Msi1 using anti-Musashi 1/Msi1 antibody (A05052-1). Musashi 1/Msi1 was detected in an immunocytochemical section of
M05052-1 · IHCIHC analysis of MSI using anti-MSI antibody (M05052-1). MSI was detected in paraffin-embedded section of human lung cancer tissue. Heat medi
M05052-1 · IHCFigure 3 IHC analysis of MSI using anti-MSI antibody (M05052-1). MSI was detected in paraffin-embedded section of human rectum cancer tissue
M05052-1 · IFIF analysis of MSI using anti-MSI antibody (M05052-1). MSI was detected in immunocytochemical section of MCF7 cells. Enzyme antigen retrieva
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000135097-MSI1/tissue/cerebral+cortex#imid_20678536
HPA · RetinaHuman Protein Atlas IHC, Retina. Source: https://www.proteinatlas.org/ENSG00000135097-MSI1/tissue/retina#imid_1250
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000135097-MSI1/tissue/colon#imid_20678462
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000135097-MSI1/tissue/liver#imid_20678455
HPA · ICC-IF AF22Human Protein Atlas immunofluorescence, AF22, antibody HPA074923; green = MSI1, blue = nucleus, red = microtubules.
HPA · ICC-IF AF22Human Protein Atlas immunofluorescence, AF22, antibody HPA074923; green = MSI1, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for MSI1 IHC & IF
🧪Run caudate first and assess staining in glial cells (HPA: Medium in caudate glial cells); use adipose tissue adipocytes as the negative tissue (HPA: Not detected in adipocytes). On the positive slide, neighboring cells without convincing MSI1 staining should remain at background; HPA identifies glial cells as the positive population but does not establish the status of every other cell type (HPA: Medium in caudate glial cells).
Positive control tissue: Caudate (Glial cells, HPA Medium)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show MSI1 in AF22, SH-SY5Y, U2OS, HAP1, with annotated localisation: Nucleoplasm (approved), Cytosol (approved) (HPA subcellular).
Technical controls: Include no-primary (secondary-only), host- and isotype-matched rabbit IgG, and MSI1-knockout material as controls (caption: rabbit anti-MSI1 primary; standard IHC practice). Quench endogenous peroxidase and check endogenous biotin when using the caption’s biotin-based DAB detection; for IF in brain tissue, assess autofluorescence with a no-primary control (caption: biotinylated secondary, streptavidin–biotin complex and DAB; standard IHC/IF practice).
⚠️Feasibility: The selected A05052-1 paraffin-section caption reports citrate pH 6 heat retrieval for 20 minutes, but does not establish that retrieval is required in caudate; its fixative and a target-specific fixation window or fixation effect are unreported (caption: A05052-1). HPA ICC-IF images support cellular IF assessment, while the supplied evidence does not establish whether IF or frozen sections are easier than paraffin IHC (HPA: ICC-IF images in AF22, SH-SY5Y, U2OS and HAP1; caption: paraffin-section IHC). For caudate IF, account for possible brain-tissue autofluorescence when interpreting signal (standard IF practice).
HPA tissue IHC evidence for MSI1
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 |
|---|---|---|---|---|
| Caudate | Glial cells | Medium | Protein (IHC) | HPA → |
| Cerebellum | Cells in molecular layer | Medium | Protein (IHC) | HPA → |
| Cerebral cortex | Glial cells | Medium | Protein (IHC) | HPA → |
| Duodenum | Glandular cells | Medium | Protein (IHC) | HPA → |
| Hippocampus | Glial cells | Medium | 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 → |
| 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 MSI1 IHC Tips
Troubleshoot MSI1 staining in paraffin section chromogenic IHC, using the catalog antibody’s tissue image and independent localisation evidence as reference points.
What retrieval conditions should I start with for weak MSI1 staining?
Start with heat-mediated retrieval in citrate buffer at pH 6 for 20 minutes (datasheet A05052-1). That condition was used for the catalog antibody’s paraffin section image; the caption does not report the fixative (datasheet A05052-1). Run a known positive section alongside the test section, then compare signal in the same cell compartment after identical DAB development (standard IHC practice; HPA: cytoplasmic and nuclear tissue staining). If staining remains weak, vary heating time cautiously while keeping the citrate buffer constant, and check for tissue damage or increased background (standard IHC practice).
Could fixation explain weak or uneven MSI1 staining?
MSI1 sensitivity to a particular fixative or fixation duration is unknown from the supplied evidence (datasheet A05052-1: fixative unreported). The catalog image establishes staining in a paraffin-embedded section, but does not establish a formalin fixation condition (datasheet A05052-1). Record each specimen’s actual fixative and processing history, and compare similarly processed positive and test sections with the same retrieval and detection run (standard IHC practice). If a new fixation condition gives weak staining, assess matched sections and morphology before assigning the difference to MSI1 biology (standard IHC practice). Do not infer fixation tolerance from MSI1 localisation or phosphorylation (UniProt O43347: cytoplasm, nucleus, phosphoserine at residue 191).
Should MSI1 staining be nuclear, cytoplasmic, or both?
Evaluate both nuclear and cytoplasmic signal: MSI1 is annotated in the nucleus and cytoplasm (UniProt O43347: subcellular location). Independent imaging places it in the nucleoplasm and cytosol, while tissue IHC reports both compartments across several tissues (HPA: approved nucleoplasm and cytosol; HPA: tissue profile). Compare staining with the nuclear counterstain and score each compartment separately when the distinction matters to the experiment (standard IHC practice). A compartment shift can be biologically interesting, but verify that it persists across comparable sections, retrieval runs and detection controls before interpreting it (standard IHC practice).
Can an unknown epitope affect interpretation of MSI1 IHC?
The supplied record lists no MSI1 isoforms and identifies two RNA recognition motifs at residues 20–110 and 109–186 (UniProt O43347: isoforms and domains). It also lists acetylation at residue 1 and phosphorylation at residue 191, without identifying this antibody’s epitope (UniProt O43347: modified residues; datasheet A05052-1: epitope unspecified). Therefore, staining cannot establish which motif, modification state or potential unlisted variant the antibody detects (supplied evidence: epitope unspecified). For a critical localisation result, compare another validated reagent with a documented epitope and use appropriate negative controls on matched sections (standard IHC practice).
How can I cross-check an MSI1 IHC pattern by immunofluorescence?
Use IF as a separate validation experiment and co-stain with a marker for the expected cell type; glial cells in cerebral cortex are one documented MSI1-positive reference (HPA: cerebral cortex glial cells, Medium). Choose a fluorophore in a channel with low measured tissue autofluorescence, and include single-channel controls before interpreting overlap (standard IF practice). MSI1 has no transmembrane segment and is reported in the cytosol and nucleoplasm, so use permeabilisation that permits antibody access to those intracellular compartments (UniProt O43347: topology; HPA: approved locations; standard IF practice). Confirm that the IF pattern agrees with the IHC cell and compartment pattern while treating the assays’ detection signals separately (standard IHC and IF practice).
How do I distinguish diffuse MSI1 signal from chromogenic background?
Begin with the catalog image conditions as a reference: 10% goat serum block, 1 µg/ml primary antibody overnight at 4°C, then biotinylated secondary and DAB detection (datasheet A05052-1). Include a primary-omission section to assess secondary and detection background, and apply an endogenous peroxidase block before DAB as a general chromogenic IHC step (standard IHC practice). Optimise antibody concentration and development time if colour appears outside identifiable cells or overwhelms the counterstain (standard IHC practice). Check the tissue edge and damaged areas separately, since uneven processing and trapped reagent can mimic a broad signal (standard IHC practice).
How should I score MSI1 staining across paraffin sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and compartment before scoring: MSI1 staining can be cytoplasmic or nuclear, and the HPA tissue profile varies by cell type (UniProt O43347: location; HPA: tissue profile). For each compartment, report the percentage of positive target cells and an H-score if staining intensity is reproducibly graded (standard IHC practice). For spatial questions, count positive cells per mm² of evaluable tissue, excluding folds, tears and necrosis under a prespecified rule (standard IHC practice). Normalise counts to the relevant cell population or measured evaluable area, and keep retrieval, detection and imaging settings consistent across comparisons (standard IHC practice).
What makes an MSI1-positive IHC result convincing?
A convincing result has identifiable cellular signal in the nucleus or cytoplasm and fits the sampled cell population (UniProt O43347: location; HPA: tissue profile). For example, medium staining in retinal ganglion cells is documented, whereas adipocytes in adipose tissue are reported as undetected (HPA: retina; HPA: adipose tissue). Treat staining confined to tissue edges, necrosis or the primary-omission control as a reason to investigate artefact or detection background (standard IHC practice). Also check the endogenous peroxidase control before calling DAB deposits MSI1-positive, and interpret unexpected compartments against the counterstain and a comparable positive section (standard IHC practice).
Boster reagents
Best MSI1 / RNA-binding protein Musashi homolog 1 IHC Antibodies
The catalog shows MSI1 IHC in paraffin sections of human lung cancer and IF/ICC in MCF7 cells; both antibodies list human, mouse, and rat reactivity (catalog image captions; catalog applications and reactivity).
Real IHC data
Anti-Musashi 1/Msi1 Antibody ®
Cat # A05052-1
Real IHC data
Anti-Musashi 1/Msi1 Antibody ® (monoclonal, 2B9)
Cat # M05052-1
A05052-1 will render with a human lung cancer IHC image; its other IHC captions show mouse intestine, rat intestine, and rat brain, and its IF captions show MCF7 cells and human and mouse tissue (A05052-1 image captions). M05052-1 will render with a human lung cancer IHC image; another IHC caption shows human rectum cancer, and its IF caption shows MCF7 cells (M05052-1 image captions).
Which to pick: For paraffin-section IHC, choose A05052-1 when evidence across species matters: its captions show human, mouse, and rat tissue with citrate retrieval (pH 6, 20 minutes); the mouse monoclonal M05052-1 (clone 2B9) has human tissue captions with EDTA retrieval (pH 8) (catalog IHC captions; catalog clone). For IF/ICC, A05052-1 has MCF7 and tissue IF examples, while M05052-1 has an MCF7 IF example; both list IF and ICC (catalog IF captions; catalog applications). The IHC captions describe paraffin sections but do not report the fixative (catalog IHC captions).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry O43347 (MSI1H_HUMAN, RNA-binding protein Musashi homolog 1).
- Human Protein Atlas. MSI1 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. MSI1 subcellular location (ICC-IF): Localized to the nucleoplasm and cytosol..
- Human Protein Atlas. MSI1 antibody validation summary (2 antibodies).
- Osteoarticular Expression of Musashi-1 in an Experimental Model of Arthritis. BioMed research international 2015 — PMC4433648.
- The Musashi-1-type 2 deiodinase pathway regulates astrocyte proliferation. The Journal of biological chemistry 2024 — PMC11301063.
- Msi1 promotes tumor growth and cell proliferation by targeting cell cycle checkpoint proteins p21, p27 and p53 in cervical carcinomas. Oncotarget 2014 — PMC4279416.
- Musashi1, a potential prognostic marker in esophageal squamous cell carcinoma. Oncology reports 2017 — PMC5549024.
- PubMed PMID:9790759 — UniProt-cited evidence.
- PubMed PMID:16541075 — UniProt-cited evidence.
- PubMed PMID:12054577 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for MSI1 (RNA-binding protein Musashi homolog 1). Expected localisation Cytoplasmic and nuclear tissue staining (HPA tissue IHC). Antigen retrieval: Citrate pH 6 HIER, heat-mediated (datasheet A05052-1). Validated IHC antibody: A05052-1 at 0.5-1μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Caudate (Glial cells); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human lung cancer tissues; fixative not specified (datasheet A05052-1); 2. Fixation: Image fixative and duration unreported (datasheet A05052-1); 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 retrieval: Citrate pH 6 , 20 min (datasheet A05052-1); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A05052-1); 8. Primary antibody: Rabbit anti-MSI1, 0.5-1μg/ml (datasheet A05052-1); 9. Primary incubation: Overnight at 4 °C (datasheet A05052-1). Watch for: Fixation: Keep fixation consistent across paraffin sections (standard IHC practice; not target-specific); Caveat: Antibody staining and RNA have medium consistency (HPA tissue IHC); Isoform / epitope: No annotated isoforms; one 1–362 chain (UniProt); Regulation: Fetal and adult tissue expression differs (UniProt). Evidence: UniProt O43347, HPA tissue IHC · Enhanced, HPA ICC-IF · nucleoplasm and cytosol., Datasheet A05052-1, PMC4433648, PMC11301063. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/MSI1/immunohistochemistry-ihc-guide.