HDAC9 Antibody

What is the molecular weight of HDAC9 protein when detected by Western blot?

HDAC9 typically appears at approximately 130-140 kDa on Western blots, which is slightly higher than its calculated molecular weight of 111 kDa. This discrepancy is due to post-translational modifications and the presence of multiple isoforms. When working with HDAC9 antibodies, it's important to note that:

• The calculated molecular weight based on amino acid sequence is approximately 111 kDa for the full-length protein (1011 amino acids)

• The observed molecular weight in Western blots is typically 130-140 kDa

• Different isoforms may appear at varying molecular weights

When troubleshooting Western blot detection, always verify the expected band size for your specific cell type, as expression patterns may vary across tissues .

What are the available types of HDAC9 antibodies and their optimal applications?

Various types of HDAC9 antibodies are available for different research applications:

For optimal results, each antibody should be titrated in your specific experimental system rather than relying solely on manufacturer recommendations .

What is the tissue expression pattern of HDAC9 that I should consider when selecting controls?

HDAC9 shows a tissue-specific expression pattern that should inform your experimental design:

• Highest expression: Brain, heart, skeletal muscle, and testis

• Moderate expression: Kidney, placenta, and pancreas

• Expression in cancer: Upregulated in certain cancers, including gastric cancer

When selecting positive controls for HDAC9 antibody validation, HeLa nuclear extracts are commonly used . Additionally, Western blot detection has been validated in multiple cell lines including HeLa, Daudi, HepG2, Raji, K-562, and Ramos cells .

For negative controls, HDAC9 knockout cell lines have been used to verify antibody specificity, as demonstrated by the absence of bands in HDAC9 knockout HAP1 cells .

How should I optimize Western blot protocols for HDAC9 detection?

For optimal Western blot detection of HDAC9, consider these methodological improvements:

• Extraction method: As HDAC9 is a chromatin-bound protein, it may not be fully soluble in low-salt nuclear extracts. Use a high salt/sonication protocol when preparing nuclear extracts to improve extraction efficiency .

• Antibody dilution:

  • For monoclonal antibodies: 1:1000-1:4000

  • For polyclonal antibodies: 1:500-1:2000

• Blocking: Use 5% non-fat milk in TBST for 1 hour at room temperature.

• Detection systems: For increased sensitivity, consider using IRDye-conjugated secondary antibodies. This approach has been validated using:

  • Goat anti-Rabbit IgG H&L (IRDye® 800CW) preabsorbed

  • Goat anti-Mouse IgG H&L (IRDye® 680RD) preabsorbed

• Controls: Include both positive controls (HeLa nuclear extract) and, if available, HDAC9 knockout samples to verify specificity .

For cell-specific optimization, validated Western blot detection has been successful in HeLa, Daudi, HepG2, Raji, K-562, and Ramos cells .

What are the recommended protocols for immunohistochemistry (IHC) using HDAC9 antibodies?

For effective immunohistochemical detection of HDAC9 in tissue sections:

• Antigen retrieval: Heat-mediated antigen retrieval in citrate buffer (pH 6.0) or Epitope Retrieval Solution 2 (pH 9.0) has proven effective .

• Primary antibody incubation:

  • Dilution: 1:500 for rabbit anti-human HDAC9 antibody

  • Incubation: 37°C for 2 hours

• Detection system: Use an appropriate IHC detection kit compatible with the primary antibody host species (e.g., anti-rabbit immunohistochemistry kit) .

• Visualization: DAB (3,3'-diaminobenzidine) solution with hematoxylin counterstaining provides good contrast .

• Scoring system: A validated scoring method combines intensity and proportion scores:

  • Proportion score (based on percentage of positive cells):
    0 (<5%), 1 (5-25%), 2 (26-50%), 3 (51-75%), 4 (>75%)

  • Intensity score:
    0 (no signal), 1 (weak), 2 (moderate), 3 (strong)

  • Final IHC score = proportion score × intensity score (range: 0-12)

  • Classification: Low (0-4), Intermediate (5-7), High (8-12)

For accurate assessment, scores should be determined by two pathologists blinded to clinical data .

How can I verify the specificity of my HDAC9 antibody?

To ensure antibody specificity and avoid misleading results:

• Peptide competition assay: Pre-incubate the antibody with its specific antigenic peptide. The disappearance of signal in Western blot confirms specificity, as demonstrated in the analysis of HDAC9 expression in HepG2 cell lysates .

• Knockout validation: Test the antibody on HDAC9 knockout cell lines or tissues. Specific antibodies should show no signal in knockout samples, as validated with HDAC9 antibody [EPR5223] in wild-type vs. HDAC9 knockout HAP1 cells .

• Multiple antibody comparison: Use antibodies targeting different epitopes of HDAC9 to confirm consistent detection patterns.

• Recombinant protein control: Include purified recombinant HDAC9 protein as a positive control.

• Cross-reactivity assessment: Test the antibody on related HDACs (particularly other Class IIa HDACs) to ensure it does not cross-react. For example, specificity has been demonstrated where anti-FLAG antibody co-precipitated ATDC with FLAG-tagged HDAC9 but not with FLAG-tagged HDAC7 .

How does HDAC9 interact with other proteins, and how can these interactions be studied using HDAC9 antibodies?

HDAC9 participates in multiple protein-protein interactions that regulate its function and biological activity. These interactions can be studied using various antibody-based techniques:

• Identified interaction partners:

  • ATDC (TRIM29): Co-purifies with HDAC9 and interacts with its C-terminal region (residues 601-1011)

  • HDAC1, HDAC3: Direct interactions demonstrated

  • MEF2: HDAC9 represses MEF2-dependent transcription

  • RBP-Jk: Interaction in the Notch pathway

  • IKK complex members: Interaction in the NF-κB pathway

  • Additional partners: CTBP1, MAPK10, ETV6, NCOR1, and BCL6

• Co-immunoprecipitation methodology:

  • Forward approach: Immunoprecipitate HDAC9 with anti-HDAC9 antibody and detect interaction partners by Western blotting

  • Reverse approach: Immunoprecipitate potential partners and detect HDAC9

  • Example protocol: Prepare cell lysate from cells expressing tagged proteins (e.g., FLAG-HDAC9 and HA-ATDC), immunoprecipitate with anti-HA antibody, and analyze precipitates by Western blot with anti-FLAG antibody

• Affinity purification coupled with mass spectrometry:

  • Express FLAG-HA-tagged HDAC9 in cells

  • Purify using sequential anti-FLAG and anti-HA affinity chromatography

  • Identify novel interacting proteins by mass spectrometry

When studying these interactions, it's important to include appropriate controls, such as immunoprecipitation with preimmune serum or no primary antibody .

What is the role of HDAC9 in cancer pathogenesis, and how can HDAC9 antibodies be used in cancer research?

HDAC9 plays significant roles in various cancers, particularly in gastric cancer (GC) and hepatocellular carcinoma (HCC). HDAC9 antibodies are valuable tools for investigating these connections:

This research suggests that HDAC9-selective histone deacetylase inhibitors could potentially improve chemotherapy efficacy and reduce systemic toxicity in cancer treatment .

How does HDAC9 regulate gene expression through deacetylation, and what techniques can be used to study this activity?

HDAC9, as a Class IIa histone deacetylase, regulates gene expression through complex mechanisms:

• Molecular mechanism of HDAC9-mediated deacetylation:

  • HDAC9 removes acetyl groups from lysine residues on the N-terminal tails of core histones (H2A, H2B, H3, and H4)

  • This deacetylation leads to chromatin condensation and transcriptional repression

  • Beyond histones, HDAC9 can deacetylate non-histone proteins like ATDC, altering their functional interactions with other proteins (e.g., p53)

• Techniques to study HDAC9 deacetylase activity:

  • Chromatin immunoprecipitation (ChIP): To identify genomic regions bound by HDAC9

  • Histone acetylation assays: To measure changes in global or locus-specific histone acetylation levels

  • Reporter gene assays: To assess the impact of HDAC9 on transcriptional activity

  • Co-immunoprecipitation: To identify proteins deacetylated by HDAC9

  • Mass spectrometry: To identify specific lysine residues targeted by HDAC9

• Functional roles in specific pathways:

  • Repression of MEF2-dependent transcription

  • Interactions with the Notch pathway through RBP-Jk

  • Modulation of NF-κB pathway through IKK complex members

  • Regulation of p53 activity through ATDC deacetylation

These mechanisms contribute to HDAC9's roles in cell differentiation, proliferation, apoptosis, and various disease states .

What are common technical challenges when working with HDAC9 antibodies and how can they be resolved?

Researchers frequently encounter several technical issues when using HDAC9 antibodies:

• Multiple bands in Western blots:

  • Cause: HDAC9 exists in multiple isoforms (HDAC9 isoforms 1-4)

  • Solution: Verify band patterns with positive controls and isoform-specific information. Consider using knockout samples to confirm specificity .

• High background in immunohistochemistry:

  • Cause: Insufficient blocking or antibody cross-reactivity

  • Solution: Optimize blocking conditions (5% BSA or 10% normal serum from secondary antibody species) and increase washing steps. Validate with peptide competition assays .

• Low signal in nuclear fractions:

  • Cause: HDAC9 can be difficult to extract as it is chromatin-bound

  • Solution: Use high salt/sonication extraction protocols specifically recommended for chromatin-bound proteins .

• Inconsistent results across applications:

  • Cause: Antibodies may perform differently in various applications

  • Solution: Select antibodies validated specifically for your application of interest. For example, some antibodies are validated for WB but not for IHC .

• Cross-reactivity with other HDACs:

  • Cause: Sequence similarity between HDAC family members

  • Solution: Use antibodies targeting unique regions of HDAC9. Verify specificity by testing with other HDAC family members as controls. For example, HDAC9-ATDC interaction is specific and not observed with HDAC7 .

• Batch-to-batch variability:

  • Cause: Manufacturing differences between antibody batches

  • Solution: Always validate new antibody batches against previous ones using consistent positive controls.

How can I design effective experiments to study HDAC9 function using antibody-based techniques?

To effectively investigate HDAC9 function using antibody-based approaches:

How do I interpret contradictory results when using different HDAC9 antibodies?

When faced with contradictory results using different HDAC9 antibodies:

• Epitope differences:

  • Map the epitopes recognized by each antibody

  • N-terminal antibodies may detect different isoforms than C-terminal antibodies

  • Solution: Use antibodies targeting different epitopes as complementary approaches

• Isoform specificity:

  • HDAC9 exists in multiple isoforms that may have different functions

  • Some antibodies detect all isoforms while others are isoform-specific

  • Example: Antibodies targeting the C-terminal region (residues 601-1011) will detect full-length HDAC9 but may miss truncated isoforms

• Post-translational modifications:

  • Phosphorylation, SUMOylation, or other modifications may affect epitope accessibility

  • Different antibodies may have varying sensitivity to modified HDAC9

  • Approach: Use phospho-specific antibodies when studying regulation by phosphorylation

• Technical validation:

  • Implement rigorous validation using multiple methods:

    • Peptide competition assays

    • Knockout/knockdown controls

    • Recombinant protein controls

  • Example: The specificity of anti-HDAC9 antibody [EPR5223] was validated using HDAC9 knockout HAP1 cells

• Standardized protocols:

  • Maintain consistent experimental conditions when comparing antibodies

  • Document detailed protocols including blocking agents, incubation times, and detection methods

How does HDAC9 contribute to normal cellular physiology and disease states?

HDAC9 plays crucial roles in both normal physiology and pathological conditions:

What are the most recent advances in understanding HDAC9's role in specific diseases where antibody-based detection has been crucial?

Recent advances in HDAC9 research facilitated by antibody-based detection include:

How do different HDAC9 isoforms affect antibody selection and experimental interpretation?

HDAC9 exists in multiple isoforms that can complicate antibody selection and data interpretation:

• Known isoforms and their characteristics:

  • HDAC9 exists in at least four isoforms (1-4) with different tissue expression patterns and functional roles

  • Two alternatively spliced isoforms (HDAC9 and HDAC9a) both retain the HDAC catalytic domain and deacetylase activity

  • MITR (HDAC9 isoform) lacks the deacetylase domain but retains repressor functions

• Epitope considerations for antibody selection:

  • N-terminal targeting antibodies: May detect full-length and N-terminal containing isoforms

  • C-terminal targeting antibodies: Will detect only isoforms containing the C-terminus

  • Deacetylase domain antibodies: Will detect enzymatically active isoforms but miss truncated variants

• Experimental design implications:

  • Western blot analysis: Multiple bands may represent different isoforms rather than non-specific binding

  • Functional studies: Knockdown or overexpression may affect multiple isoforms simultaneously

  • Tissue-specific expression: Different tissues may express distinct isoform profiles

• Recommended approach:

  • Use antibodies that detect specific regions to identify particular isoforms

  • For comprehensive studies, use multiple antibodies targeting different epitopes

  • Always include appropriate controls and validate in your specific experimental system

  • Document the specific epitope recognized by your antibody when reporting results