RARB Antibody

What is RARB and why is it significant in scientific research?

RARB (Retinoic Acid Receptor Beta) is a nuclear receptor that mediates retinoid signaling in morphogenesis, development, and cell differentiation. It binds as heterodimers with Retinoid X Receptors (RXRs) to retinoic acid response elements (RAREs) composed of tandem 5'-AGGTCA-3' sites known as DR1-DR5, in response to all-trans or 9-cis retinoic acid . RARB is significant in research because:

• It regulates the transition of proliferating precursor cells (carcinoma cells, neuronal precursors) to postmitotic differentiated cells

• It plays key roles in neuronal development and synaptic plasticity

• It has been implicated in cancer progression, particularly in head and neck squamous cell carcinoma

• It is required for skeletal growth, matrix homeostasis, and growth plate function in concert with RARG

What are the common applications for RARB antibodies in research?

RARB antibodies are utilized across multiple experimental approaches:

These applications allow researchers to investigate RARB expression, localization, and function in various experimental contexts.

What tissue and cell types show positive reactivity with RARB antibodies?

According to experimental validation data, RARB antibodies have shown positive reactivity in:

Tissues:

• Mouse: colon, bladder, brain tissues

• Rat: bladder, brain tissues

• Human: pancreas cancer tissue, renal cell carcinoma tissue, stomach tissue, breast cancer tissue, liver cancer tissue

Cell lines:

• Sp2/0 cells (WB)

• MCF-7 cells (IF/ICC)

• SH-SY5Y human neuroblastoma cells

• HepG2 cells

• 293T cells

Researchers should verify reactivity for their specific tissue or cell type of interest, as expression levels vary significantly.

How should samples be prepared for optimal RARB detection in immunohistochemistry?

For optimal RARB detection in IHC applications:

• Fixation: Use 4% paraformaldehyde-fixed and paraffin-embedded tissues

• Sectioning: Prepare serial 4-μm-thick sections

• Deparaffinization: Complete thorough deparaffinization

• Peroxidase inactivation: Soak with 3% hydrogen peroxide

• Antigen retrieval:

  • Primary method: 10 mM citrate buffer (pH 6.0) with boiling for 10 minutes followed by cooling at room temperature for 20 minutes

  • Alternative method: TE buffer pH 9.0 for certain antibodies

• Blocking: PBS supplemented with 5% BSA to reduce background

• Antibody incubation: Incubate with primary antibodies overnight at 4°C followed by secondary antibodies at room temperature for 60 minutes

• Detection: Use a DAB Detection Kit for signal visualization

This protocol has been demonstrated effective for RARB detection in multiple tissue types.

What are the appropriate controls for validating RARB antibody specificity?

Proper controls are essential for confirming RARB antibody specificity:

• Negative controls:

  • Omission of primary antibody

  • Isotype control antibody (Rabbit IgG for most RARB antibodies)

  • RARB knockout/knockdown cells or tissues (demonstrated in published literature)

  • Mutant BRARE (beta retinoic acid response element) or RXRE (retinoid X response element) DNA probes for gel shift assays

• Positive controls:

  • Recombinant RARB protein (for Western blot)

  • Tissues known to express RARB (e.g., neuroblastoma cell lines, MCF-7 cells)

  • Peptide competition assay using the immunizing peptide (e.g., PEP-005 for certain antibodies)

  • Supershift assays with RARα and RARB antibodies for EMSA experiments

• Cross-reactivity assessment:

  • Testing for potential cross-reactivity with RARα and RARγ (some RARB antibodies show slight cross-reactivity with RARα)

Researchers should document these controls to demonstrate antibody specificity and reliability.

What is the molecular weight spectrum for RARB detection in Western blots?

Western blot analysis with RARB antibodies typically reveals:

• Calculated molecular weight: 50 kDa

• Observed molecular weight range: 37-52 kDa, depending on the specific antibody and sample preparation

• Additional bands: Some antibodies may detect an unidentified ~120 kDa protein that can be competed away with the immunizing peptide (particularly in human SH-SY5Y and COS cells)

Researchers should note that the low expression levels of RARB in native tissues often necessitate sensitive detection systems, such as enhanced chemiluminescence, for optimal visualization .

How can RARB antibodies be utilized in chromatin immunoprecipitation (ChIP) experiments?

ChIP experiments with RARB antibodies enable investigation of RARB binding to DNA response elements:

• Experimental design:

  • Use RARB antibodies for immunoprecipitation of RARB-DNA complexes

  • Include input controls and IgG negative controls

  • Consider dual ChIP with RXR antibodies to study heterodimer formation

• Applications in published research:

  • Investigation of retinoic acid's role in body axis extension

  • Study of BRARE (beta retinoic acid response element) interactions

  • Analysis of RARB binding to retinoid response elements in cancer models

• Technical considerations:

  • Ensure sufficient antibody specificity through validation experiments

  • Optimize crosslinking conditions for nuclear receptor-DNA interactions

  • Consider sequential ChIP to identify co-regulatory proteins in the complex

This approach provides crucial insights into the genomic targets of RARB and its role in transcriptional regulation.

How do different RARB antibodies compare when studying RARβ and RARγ synergistic effects?

Research on RARβ and RARγ synergism requires careful antibody selection:

• Antibody specificity requirements:

  • Use RARB antibodies with minimal cross-reactivity to RARγ

  • Consider antibodies targeting different epitopes than those affected by agonist binding

  • Validate specificity in the presence of selective ligands (e.g., BMS641, BMS961)

• Experimental approaches:

  • Use antibodies in Western blot to confirm receptor expression levels

  • Apply immunofluorescence to analyze subcellular localization

  • Employ ChIP to examine differential DNA binding in response to selective agonists

• Research applications:

  • Investigation of synergistic RARβ and RARγ activation in neuronal differentiation

  • Analysis of differential gene expression through transcriptomic approaches

  • Assessment of specific marker expression (Th, Chat) in response to receptor activation

When studying synergistic effects, researchers should carefully document receptor expression levels and consider the impact of ligand binding on epitope availability.

What methodologies are most effective for studying RARB in MSI gastric cancer models?

For researching RARB in microsatellite instability (MSI) gastric cancer:

• Tissue preparation and antibody selection:

  • Use RARB antibodies validated for human gastric cancer tissues

  • Ensure appropriate antigen retrieval with 10 mM sodium citrate (pH 6)

  • Include parallel staining for CD3, CD8, and CD68 to characterize the immune microenvironment

• Analytical approaches:

  • Compare RARB expression between MSI and microsatellite stable (MSS) gastric cancer samples

  • Evaluate correlation between RARB expression and clinical parameters

  • Analyze relationship between RARB levels and immune cell infiltration

• Complementary techniques:

  • Combine IHC with gene expression analysis

  • Validate findings through cell culture models

  • Consider xenograft models to examine RARB modulation in vivo

Research has identified RARB downregulation in human gastric cancer tissues compared to paired normal tissues, suggesting a potential role in MSI-related oncogenesis .

What are common causes of inconsistent RARB antibody staining in IHC applications?

Inconsistent RARB staining can result from several factors:

• Fixation variables:

  • Overfixation can mask epitopes

  • Inconsistent fixation times between samples

  • Variation in fixative composition

• Antigen retrieval challenges:

  • Insufficient heating during retrieval

  • Incorrect buffer pH (optimal is typically pH 6.0 with citrate buffer, though some antibodies perform better with TE buffer pH 9.0)

  • Inadequate cooling period after heat-induced retrieval

• Antibody-related issues:

  • Suboptimal antibody dilution (recommended range: 1:50-1:500)

  • Insufficient incubation time

  • Antibody degradation due to improper storage

  • Lot-to-lot variability

• Tissue-specific considerations:

  • Endogenous peroxidase activity not adequately quenched

  • Autofluorescence in certain tissues

  • Variable RARB expression levels across different samples

To address these issues, researchers should perform systematic optimization with control tissues and maintain consistent protocols across all samples.

How can signal-to-noise ratio be improved in RARB Western blot detection?

To enhance signal-to-noise ratio in RARB Western blots:

• Sample preparation optimization:

  • Use fresh samples when possible

  • Include protease inhibitors during extraction

  • Optimize protein loading (typically 20-50 μg total protein)

• Blocking strategy refinement:

  • Test different blocking agents (BSA vs. non-fat milk)

  • Extend blocking time to reduce background

  • Consider addition of 0.1-0.3% Tween-20 in washing steps

• Antibody dilution and incubation:

  • Test a range of antibody dilutions (1:1000-1:4000 recommended)

  • Extend primary antibody incubation (overnight at 4°C)

  • Use antibody diluent containing 0.1-0.2% BSA

• Detection system selection:

  • Use enhanced chemiluminescence for low abundance detection

  • Consider fluorescent secondary antibodies for multiplexing

  • Optimize exposure times with incremental imaging

• Technical considerations:

  • Ensure complete protein transfer to membrane

  • Verify uniform gel loading with housekeeping proteins

  • Consider using PVDF membranes for better protein retention

Given the low expression levels of RARB in many tissues, these optimization steps are particularly important for successful detection.

What strategies can address potential cross-reactivity with other RAR family members?

Managing cross-reactivity between RAR family members requires:

• Antibody selection based on epitope:

  • Choose antibodies targeting unique regions of RARB

  • Review cross-reactivity data in product documentation

  • Consider antibodies raised against C-terminal peptides, which often show greater specificity

• Validation approaches:

  • Perform peptide competition assays with specific RARB peptides

  • Include RAR knockout/knockdown controls when available

  • Use recombinant RARα, RARB, and RARγ proteins as controls

• Experimental design considerations:

  • Include positive controls expressing only RARB

  • Compare staining patterns with known RARα and RARγ expression patterns

  • Apply supershift assays with specific antibodies in EMSA experiments

• Technical refinements:

  • Optimize antibody dilution to minimize cross-reactivity

  • Adjust washing conditions to remove weakly bound antibodies

  • Consider pre-adsorption with recombinant RARα or RARγ for critical applications

These approaches are particularly important when studying tissues that express multiple RAR isoforms simultaneously.

How are RARB antibodies being utilized in cancer research beyond detection?

RARB antibodies are increasingly employed in cancer research for:

• Prognostic biomarker evaluation:

  • Analysis of RARB expression in relation to clinical outcomes

  • Correlation studies with treatment response

  • Examination of RARB expression in relation to cancer stage and grade

• Mechanistic studies:

  • Investigation of ALDH1A2-dependent retinoic acid signaling in head and neck squamous cell carcinoma

  • Analysis of RARB downregulation in gastric cancer

  • Examination of RARB methylation and expression changes in various cancer types

• Therapeutic targeting approaches:

  • Evaluation of RARB modulation in response to experimental treatments

  • Assessment of combination therapies targeting RARB pathways

  • Development of therapeutic strategies based on RARB status

• Tumor microenvironment interactions:

  • Analysis of RARB expression in relation to immune cell infiltration

  • Investigation of stromal-epithelial RARB signaling

  • Evaluation of RARB in cancer stem cell populations

These applications extend beyond simple detection to provide mechanistic insights into cancer biology and potential therapeutic interventions.

What are the considerations for using RARB antibodies in RosettaAntibodyDesign for therapeutic development?

When utilizing RosettaAntibodyDesign (RAbD) for RARB antibody engineering:

• Target epitope selection:

  • Consider functional domains within RARB that affect ligand binding or DNA binding

  • Analyze accessible regions based on RARB crystal structures

  • Select epitopes with minimal conservation with other RAR family members

• Framework considerations:

  • Use the North/Dunbrack CDR definition as outlined in clustering papers

  • Apply ParatopeSiteConstraints to maintain CDRs facing the antigen surface

  • Consider ParatopeEpitopeSiteConstraints to target specific RARB epitopes

• Design optimization strategies:

  • Alternate outer and inner Monte Carlo cycles as described in the RAbD protocol

  • Randomly choose CDRs from those set to design

  • Select clusters and structures from the database according to input instructions

• Validation approaches:

  • Test designed antibodies against recombinant RARB

  • Evaluate cross-reactivity with other RAR family members

  • Assess binding affinity and specificity using multiple methodologies

RAbD provides a generalized framework for antibody design that can be tailored to create RARB antibodies with improved binding affinity, stability, or functional properties.

How can RARB antibodies contribute to understanding retinoic acid's role in neuronal development?

RARB antibodies offer valuable tools for investigating retinoic acid signaling in neural development:

• Developmental timeline analysis:

  • Track RARB expression during critical developmental windows

  • Correlate expression with neuronal differentiation markers

  • Examine changes in receptor levels following retinoic acid treatment

• Cell type-specific investigations:

  • Use immunofluorescence to identify RARB-expressing neural populations

  • Combine with markers for neuronal subtypes (Th, Chat)

  • Analyze RARB in relation to glial markers (Gfap, Olig2)

• Mechanistic studies:

  • Apply ChIP to identify RARB genomic targets during differentiation

  • Investigate RARB-RXR heterodimer formation in neural precursors

  • Examine RARB binding to retinoic acid response elements with EMSA

• Functional assessments:

  • Combine with knockout/knockdown approaches to assess causality

  • Analyze synergistic effects of RARβ and RARγ activation on neuronal maturation

  • Evaluate impact of selective RARβ agonists on neural differentiation

Research has demonstrated that synergistic activation of RARβ and RARγ by selective ligands induces cell maturation to specialized neuronal subtypes, highlighting the importance of RARB in neurodevelopmental processes .