BUD9 Antibody

What is the Bud9p protein and why are antibodies against it important for yeast research?

Bud9p is a transmembrane protein in Saccharomyces cerevisiae that functions as a spatial marker for bud site selection, particularly at the distal pole of the cell. Bud9p is highly concentrated at the distal pole of yeast form (YF) cells, and its deletion leads to preferentially unipolar distal budding patterns . Antibodies against Bud9p are crucial research tools because they allow for precise detection of this protein's localization, expression levels, and interactions with other proteins such as Bud8p.

Through immunofluorescence microscopy using epitope-tagged versions of Bud9p (like myc-Bud9p), researchers have determined that Bud9p is highly concentrated at the site of incipient bud formation in unbudded cells and at the tip of growing daughter cells . These antibodies enable visualization and tracking of Bud9p during the cell cycle, providing insights into fundamental mechanisms of cell polarity and morphogenesis in yeast.

How does the structure of Bud9p influence antibody selection and experimental design?

The structure of Bud9p significantly impacts antibody selection and experimental design. Bud9p consists of an N-terminal extracellular domain (460 amino acids), a membrane-spanning domain, a short cytoplasmic loop (38 amino acids), a second membrane-spanning domain, and a short (2 amino acids) extracellular domain at the C-terminus . This structure presents several considerations:

• The large N-terminal extracellular domain provides numerous potential epitopes accessible in non-denaturing conditions, making this region favorable for antibodies intended for immunofluorescence of intact cells.

• When designing experiments, researchers must consider the membrane-associated nature of Bud9p. Membrane-dissolving detergents are required for full extraction of the protein .

• Bud9p appears to be glycosylated, as its apparent molecular weight is higher than calculated when analyzed by SDS-PAGE . This affects how antibodies may recognize the protein in different applications.

• The physical interaction between Bud8p and Bud9p means antibodies must be carefully validated to ensure specificity and avoid cross-reactivity with Bud8p.

For comprehensive detection, researchers may employ multiple antibodies targeting different regions, ensuring detection regardless of protein conformation or modification state.

What are the critical differences between using antibodies against native Bud9p versus epitope-tagged versions?

When investigating Bud9p, researchers must consider key differences between using antibodies against the native protein versus epitope-tagged versions:

Antibodies against native Bud9p:

• Detect the protein in its natural state without potential interference from tags

• Enable studies in wild-type strains without genetic manipulation

• May recognize multiple epitopes, increasing detection sensitivity

• Often require extensive validation to ensure specificity

• May have limited availability due to challenges in generating antibodies against yeast proteins

Antibodies against epitope-tagged Bud9p:

• Utilize well-characterized, highly specific commercial antibodies (e.g., anti-myc for myc-Bud9p)

• Allow for consistent detection across different experimental conditions

• Enable easier comparison between different proteins tagged with the same epitope

• Require confirmation that the tag doesn't interfere with protein function

• Necessitate genetic modification of strains to incorporate the tag

What are optimal protocols for using BUD9 antibodies in immunofluorescence microscopy?

For effective immunofluorescence microscopy with BUD9 antibodies, researchers should follow these optimized protocols:

Cell preparation and fixation:

• Grow yeast cells to mid-log phase in appropriate media

• Fix cells with 3.7% formaldehyde for 30-60 minutes at room temperature

• Wash cells thoroughly with phosphate buffer to remove fixative

• Digest cell walls with zymolyase (100T, 1 mg/ml) in sorbitol buffer for 20-30 minutes

• Permeabilize with a gentle detergent (0.1% Triton X-100) for 5-10 minutes

Immunostaining procedure:

• Block with 3-5% BSA or normal serum for 30-60 minutes

• Incubate with primary BUD9 antibody (1:100 to 1:500 dilution) overnight at 4°C

  • For epitope-tagged versions, use anti-tag antibodies (e.g., anti-myc for myc-Bud9p)

• Wash extensively (4-5 times) with PBS containing 0.1% Tween-20

• Apply fluorophore-conjugated secondary antibodies (1:500 to 1:2000) for 1-2 hours at room temperature

• Wash thoroughly to remove unbound antibodies

• Counterstain with DAPI (1 μg/ml) to visualize nuclei

• Mount slides with anti-fade mounting medium

Controls and validation:

• Include wild-type and bud9Δ strains as positive and negative controls

• For co-localization studies, use established markers of cellular structures

• When using epitope-tagged Bud9p, verify that the localization pattern matches expected distribution

This approach has successfully demonstrated that myc-Bud9p is highly concentrated at the site of incipient bud formation in unbudded cells and at the tip of growing daughter cells , providing a reference pattern for validation.

How should researchers optimize Western blot protocols for Bud9p detection?

Optimizing Western blot protocols for reliable Bud9p detection requires addressing several technical challenges:

Sample preparation:

• Lyse cells using mechanical disruption (glass beads) with appropriate lysis buffer

• Include membrane-dissolving detergents (0.5-1% SDS or Triton X-100) as Bud9p is a transmembrane protein

• Add complete protease inhibitor cocktail to prevent degradation

• Keep samples cold throughout preparation

• Centrifuge at 12,000-14,000g for 10-15 minutes to remove cell debris

Electrophoresis and transfer:

• Load equal amounts of total protein (30-50 μg) per lane

• Use gradient gels (4-15%) for better resolution of potentially glycosylated Bud9p

• Run gels at constant voltage (90-120V) until adequate separation

• For transfer, use PVDF membranes with 0.1% SDS in transfer buffer

• Transfer at lower voltage for extended time (30V overnight) to ensure complete transfer of high molecular weight forms

Antibody incubation and detection:

• Block membranes with 5% non-fat milk or BSA in TBST for 1 hour

• Incubate with primary BUD9 antibody (1:1000 to 1:5000) overnight at 4°C

• Wash extensively (5-6 times, 5-10 minutes each) with TBST

• Apply HRP-conjugated secondary antibody (1:5000 to 1:10000) for 1 hour at room temperature

• Wash thoroughly to reduce background

• Detect using enhanced chemiluminescence with appropriate exposure times

Critical considerations:

• Bud9p appears to be glycosylated, as its apparent molecular weight is higher than calculated when analyzed by SDS-PAGE

• Include positive controls (wild-type lysate) and negative controls (bud9Δ lysate)

• For quantification, normalize to stable loading controls

• When using epitope-tagged versions, antibodies against the tag (e.g., anti-myc) often provide cleaner results

This methodological approach accounts for the membrane-associated nature of Bud9p and its potential post-translational modifications, ensuring reliable detection and quantification.

What strategies effectively validate BUD9 antibody specificity?

Rigorous validation of BUD9 antibody specificity is essential for reliable experimental results. A comprehensive validation strategy includes:

Genetic validation approaches:

• Compare antibody signal between wild-type and bud9Δ deletion strains

  • Signal should be present in wild-type cells but absent in deletion mutants

  • This represents the gold standard for antibody validation

• Test antibodies in strains overexpressing BUD9 from high-copy plasmids or inducible promoters

  • Signal intensity should correlate with expression levels

Epitope-tagged control experiments:

• Use strains expressing epitope-tagged versions of Bud9p (such as myc-Bud9p)

• Perform parallel detection with antibodies against both Bud9p and the epitope tag

• Compare localization patterns and signal intensities

• Confirm that phenotypic analysis of tagged versions shows no difference compared to non-tagged versions

Biochemical validation methods:

• Peptide competition assays

  • Pre-incubate antibody with the immunizing peptide before application

  • Specific signal should be blocked while non-specific binding remains

• Western blot analysis

  • Verify single band of expected molecular weight (accounting for glycosylation)

  • Compare with migration pattern of epitope-tagged versions

Cross-reactivity assessment:

• Test for recognition of Bud8p, which shares structural similarities and interacts with Bud9p in vivo

• Evaluate signal in cells with altered levels of related proteins

• Perform immunoprecipitation followed by mass spectrometry to identify all proteins recognized

Multi-technique validation:

• Verify consistent results across different applications (immunofluorescence, Western blotting, immunoprecipitation)

• Confirm that observed localization patterns match published data

  • Bud9p should be highly concentrated at the distal pole of YF cells and at sites of incipient bud formation

Thorough validation using multiple complementary approaches ensures reliable antibody performance across different experimental contexts.

How can BUD9 antibodies reveal protein localization changes during the yeast cell cycle?

BUD9 antibodies provide valuable insights into the dynamic localization of Bud9p throughout the cell cycle. A comprehensive experimental approach includes:

Synchronization and time-course analysis:

• Synchronize yeast cultures using:

  • Alpha-factor arrest-release for MATa cells

  • Nocodazole treatment for mitotic arrest

  • Elutriation to separate cells by size/cell cycle stage

• Collect samples at regular intervals (10-15 minutes) after synchrony release

• Process parallel samples for:

  • Immunofluorescence with BUD9 antibodies

  • Flow cytometry to confirm cell cycle positions

  • Budding index determination by microscopy

Quantitative localization analysis:

• Perform immunofluorescence with BUD9 antibodies or antibodies against epitope-tagged Bud9p

• Categorize cells by cell cycle stage based on morphology and DNA staining

• Score Bud9p localization patterns in at least 200 cells per timepoint

• Quantify signal intensity at different cellular locations (distal pole, incipient bud site, bud tip)

• Generate quantitative distribution maps of Bud9p throughout the cell cycle

Co-localization with cell cycle markers:

• Perform dual-label immunofluorescence with markers for:

  • Polarisome components (Spa2p, Bni1p)

  • Septin ring (Cdc3p, Cdc12p)

  • Cell cycle regulators (Cdc28p, cyclins)

• Calculate co-localization coefficients using digital image analysis

• Correlate changes in Bud9p localization with specific cell cycle events

Research has revealed that Bud9p is highly concentrated at the site of incipient bud formation in unbudded cells and at the tip of growing daughter cells . The subcellular localization pattern of myc-Bud9p has been observed throughout the cell cycle using immunofluorescence microscopy . Interestingly, BUD9 expression shows cell cycle regulation, with peak expression in G1 phase , suggesting coordination between protein expression and localization during the cell cycle.

What protocols enable effective co-immunoprecipitation of Bud9p protein complexes?

Co-immunoprecipitation (co-IP) using BUD9 antibodies can effectively isolate Bud9p and its interaction partners. An optimized protocol includes:

Cell preparation and lysis:

• Grow yeast cells to mid-log phase in appropriate media

• Harvest and wash cells with ice-cold PBS

• Resuspend in lysis buffer containing:

  • Non-ionic detergent (0.5-1% NP-40 or Triton X-100)

  • Physiological salt concentration (150 mM NaCl)

  • Buffer (50 mM Tris-HCl, pH 7.5)

  • Protease inhibitor cocktail

  • Phosphatase inhibitors if studying phosphorylation states

• Lyse cells by mechanical disruption with glass beads

• Clarify lysate by centrifugation (12,000-14,000g for 10-15 minutes)

Immunoprecipitation procedure:

• Pre-clear lysate with Protein A/G beads (30-60 minutes at 4°C)

• Add BUD9 antibody or antibody against epitope tag (for tagged versions)

  • Typically 2-5 μg antibody per mg of total protein

• Incubate with gentle rotation overnight at 4°C

• Add Protein A/G beads and incubate for 2-4 hours at 4°C

• Wash beads 4-5 times with lysis buffer

• Elute bound proteins by boiling in SDS sample buffer

Analysis of co-precipitated proteins:

• Separate proteins by SDS-PAGE

• Perform Western blotting to detect specific interaction partners

• Probe with antibodies against suspected interaction partners

• For unbiased discovery, analyze by mass spectrometry

Critical controls:

• Non-specific IgG from the same species as BUD9 antibody

• Lysate from bud9Δ strains to identify non-specific interactions

• Input sample (5-10% of pre-immunoprecipitation lysate)

• Reciprocal IPs using antibodies against interaction partners

This approach has successfully demonstrated that Bud8p and Bud9p physically interact in vivo. Specifically, myc-Bud8p co-purifies with GST-Bud9p (but not with GST alone), and conversely, myc-Bud9p associates with GST-Bud8p (but not with GST control) . These findings suggest that Bud8p and Bud9p might influence each other's functions through direct physical interaction.

How can researchers use BUD9 antibodies to investigate relationships between protein modification and function?

BUD9 antibodies can be strategically employed to explore connections between Bud9p modifications and functional outcomes:

Detection of post-translational modifications:

• Immunoprecipitate Bud9p using BUD9 antibodies or antibodies against epitope tags

• Analyze samples using:

  • Phospho-specific antibodies in Western blotting

  • Glycoprotein-specific stains (PAS, lectin blotting)

  • Mass spectrometry for comprehensive modification mapping

• Compare modification patterns across different conditions:

  • Cell cycle stages

  • Nutrient availability variations

  • Stress conditions

Structure-function analysis:

• Generate strains expressing Bud9p mutants:

  • Phosphorylation site mutants (S/T to A or D/E)

  • Glycosylation site mutants (N to Q)

  • Domain deletion/truncation mutants

• Use BUD9 antibodies to confirm expression and stability of mutant proteins

• Analyze localization patterns by immunofluorescence

• Correlate modifications with:

  • Protein localization at the distal pole

  • Interaction with Bud8p and other partners

  • Budding pattern phenotypes

Temporal analysis of modifications:

• Synchronize cells and collect time-course samples

• Immunoprecipitate Bud9p from each timepoint

• Analyze modification dynamics throughout the cell cycle

• Correlate with changes in protein function and localization

Bud9p appears to be glycosylated, as its apparent molecular weight is higher than calculated when analyzed by SDS-PAGE . This glycosylation may be functionally important, given that Bud9p contains predicted N-glycosylation sites in its N-terminal domain . Furthermore, the absence of Bud9p (in bud9 deletion strains) favors distal bud initiation, defining a negative function for Bud9p at the distal pole . This suggests that post-translational modifications might regulate this negative regulatory function, providing a compelling area for investigation using BUD9 antibodies.

How can BUD9 antibodies elucidate mechanisms of asymmetric protein localization in yeast?

BUD9 antibodies serve as powerful tools for investigating the complex mechanisms underlying asymmetric protein localization in yeast:

Cytoskeletal-dependent localization:

• Treat cells with cytoskeleton-disrupting agents:

  • Latrunculin A (actin disruption)

  • Nocodazole (microtubule disruption)

• Perform immunofluorescence with BUD9 antibodies

• Quantify changes in Bud9p localization patterns

• Identify cytoskeletal elements required for proper Bud9p positioning

Vesicular trafficking analysis:

• Use temperature-sensitive mutants in secretory pathway components

• Block specific trafficking steps with inhibitors

• Analyze Bud9p localization by immunofluorescence

• Determine transport routes required for Bud9p delivery to the distal pole

Membrane domain characterization:

• Co-immunoprecipitate Bud9p with BUD9 antibodies

• Analyze lipid composition of associated membrane fragments

• Investigate co-localization with membrane domain markers

• Assess effects of membrane composition alterations on Bud9p localization

Protein sequence determinants:

• Generate strains expressing Bud9p with domain swaps or deletions

• Use BUD9 antibodies to verify expression and detect chimeric proteins

• Map sequences required for proper localization

• Compare with related proteins like Bud8p

Despite Bud9p and Bud8p having similar structures as transmembrane proteins , they localize to different regions of the cell. Both proteins lack predicted signal sequences despite having extracellular domains and potential glycosylation sites . This suggests complex trafficking mechanisms that could be elucidated using BUD9 antibodies to track protein movement through the secretory pathway and to the cell surface.

The observation that Bud9p localization patterns differ between yeast form cells and pseudohyphal cells provides an excellent model system for studying condition-dependent regulation of protein localization using BUD9 antibodies.

What methodologies combine BUD9 antibodies with systems biology approaches to study budding networks?

Integrating BUD9 antibodies with systems biology approaches creates powerful methodologies for comprehensively mapping budding networks:

Protein interaction network mapping:

• Perform large-scale co-immunoprecipitation with BUD9 antibodies

• Identify interaction partners using mass spectrometry

• Validate key interactions with reciprocal co-IPs

• Construct protein-protein interaction networks

• Compare networks across different conditions (e.g., haploid vs. diploid, various nutrient states)

The established interaction between Bud8p and Bud9p provides an important positive control for this approach .

Transcriptional regulation analysis:

• Combine chromatin immunoprecipitation (ChIP) of transcription factors with RT-qPCR of BUD9

• Correlate transcription factor binding with BUD9 expression changes

• Use BUD9 antibodies to correlate transcript and protein levels

• Identify regulatory networks controlling BUD9 expression

Research has shown that BUD9 expression is highly regulated during the cell cycle, with peak expression in G1 phase , suggesting specific transcriptional control mechanisms.

Computational modeling with experimental validation:

• Develop mathematical models of budding pattern establishment

• Generate predictions about Bud9p localization and dynamics

• Test predictions using BUD9 antibodies in targeted experiments

• Refine models based on experimental results

Multi-omics integration:

• Perform parallel analyses of:

  • Proteomics (using BUD9 antibodies for protein quantification)

  • Transcriptomics (measuring BUD9 mRNA levels)

  • Metabolomics (assessing cellular state)

• Integrate datasets to identify coordinated cellular responses

• Map Bud9p within broader regulatory networks

Genetic interaction mapping:

• Create double mutant strains combining bud9Δ with other mutations

• Use BUD9 antibodies to analyze protein level changes in response to genetic perturbations

• Identify synthetic interactions and functional relationships

• Construct genetic interaction networks

Diploid bud8Δ bud9Δ null mutants produce a random budding pattern comparable with rsr1Δ/bud1Δ strains , indicating that Bud8p and Bud9p function together within a broader network controlling bud site selection.

How can researchers leverage BUD9 antibodies to investigate evolutionary conservation of cell polarity mechanisms?

BUD9 antibodies can be strategically employed to explore evolutionary aspects of cell polarity:

Cross-species antibody applications:

• Test BUD9 antibodies against homologous proteins in related yeast species:

  • Other Saccharomyces species

  • More distant fungal relatives like Candida or Schizosaccharomyces

• Identify conserved epitopes recognized across species

• Compare localization patterns between species

• Determine conservation of protein function through complementation studies

Comparative functional analysis:

• Express tagged versions of BUD9 homologs from different species in S. cerevisiae

• Use antibodies against the tag to detect expression and localization

• Test ability to rescue bud9Δ phenotypes

• Identify functionally conserved domains and species-specific elements

Evolutionary protein engineering:

• Create chimeric proteins combining domains from BUD9 homologs across species

• Use BUD9 antibodies or tag-specific antibodies to verify expression

• Analyze localization and function of chimeric proteins

• Map evolutionarily conserved functional elements

Conservation of regulatory mechanisms:

• Compare post-translational modifications of Bud9p across species

• Analyze conservation of interaction partners identified through co-immunoprecipitation

• Examine species-specific differences in expression patterns

• Correlate with differences in budding behaviors across species

The finding that Bud9p localization and expression patterns are identical in haploid and diploid strains, despite their different budding patterns (axial vs. bipolar) , suggests that additional factors regulate the utilization of these spatial landmarks. This provides an excellent starting point for evolutionary comparisons, investigating how conserved proteins like Bud9p are differentially regulated across species to create diverse cellular behaviors.

What are common challenges in BUD9 antibody applications and their solutions?

Researchers working with BUD9 antibodies may encounter several technical challenges. Here are methodological solutions to common issues:

Weak or inconsistent immunofluorescence signal:

• Problem: Poor antibody penetration through yeast cell wall
  Solution: Optimize zymolyase treatment (concentration 0.5-2 mg/ml, time 15-45 minutes); try different cell wall digesting enzymes

• Problem: Epitope masking during fixation
  Solution: Test different fixatives (formaldehyde vs. methanol); reduce fixation time; try antigen retrieval techniques

• Problem: Low abundance of native Bud9p
  Solution: Use epitope-tagged versions (myc-Bud9p) with well-characterized antibodies ; employ signal amplification systems

Western blot detection issues:

• Problem: Multiple or smeared bands
  Solution: Address potential glycosylation by treating samples with deglycosylation enzymes; optimize SDS concentration in sample buffer; use gradient gels for better resolution

• Problem: Protein degradation
  Solution: Add protease inhibitor cocktail to lysis buffer; process samples quickly; keep samples cold throughout preparation

• Problem: Poor transfer of high molecular weight forms
  Solution: Extend transfer time; add SDS (0.1%) to transfer buffer; use PVDF membranes for better retention

Co-immunoprecipitation challenges:

• Problem: Low yield of Bud9p complexes
  Solution: Optimize detergent type and concentration for efficient membrane solubilization; increase antibody amount or incubation time; use crosslinking to stabilize transient interactions

• Problem: Non-specific binding
  Solution: Increase wash stringency; pre-clear lysates thoroughly; use specific elution with competing peptides instead of boiling

• Problem: Disruption of true interactions
  Solution: Test different lysis conditions to balance solubilization with interaction preservation; try formaldehyde crosslinking before lysis

Antibody specificity concerns:

• Problem: Cross-reactivity with Bud8p
  Solution: Pre-absorb antibody with purified Bud8p; validate with bud9Δ strains as negative controls ; use epitope-tagged versions with tag-specific antibodies

• Problem: Background in immunofluorescence
  Solution: Extend blocking time (1-2 hours with 5% BSA); add 0.1-0.3% Tween-20 to wash buffers; pre-absorb antibody with wild-type yeast lysate

These troubleshooting approaches address the specific challenges of working with Bud9p as a membrane-associated, potentially glycosylated protein with interaction partners like Bud8p .

How can researchers optimize BUD9 antibody protocols for different yeast strain backgrounds?

Adapting BUD9 antibody protocols for diverse yeast strains requires systematic optimization:

Strain-specific cell wall considerations:

• Different strain backgrounds have varying cell wall composition and thickness

• Systematically titrate zymolyase concentration (0.5-2 mg/ml) and treatment time (10-45 minutes)

• Monitor spheroplast formation microscopically to determine optimal conditions

• For particularly resistant strains, combine enzymatic treatment with brief DTT pre-treatment

Fixation optimization:

• Test fixation conditions across strain backgrounds:

  • Formaldehyde concentration (2-4%)

  • Fixation time (15-60 minutes)

  • Temperature (room temperature vs. 4°C)

• Validate fixation quality by assessing cell morphology preservation

• For sensitive epitopes, try methanol fixation or quick formaldehyde fixation

Antibody dilution adaptation:

• Perform systematic antibody titrations for each strain background

• Create a strain optimization matrix:

  • Test 3-4 antibody dilutions

  • Vary blocking conditions (3-5% BSA or normal serum)

  • Adjust incubation times (1 hour to overnight)

• Quantify signal-to-noise ratio for each condition to determine optimal parameters

Extraction buffer modifications:

• For Western blotting and immunoprecipitation, test different lysis methods:

  • Mechanical disruption parameters (vortexing time, bead quantity)

  • Detergent type and concentration

  • Buffer composition (salt concentration, pH)

• Verify extraction efficiency by total protein quantification

• Confirm Bud9p extraction by Western blotting

Research has demonstrated that epitope-tagged versions of BUD8 and BUD9 in wild-type as well as bud8 or bud9 mutant strains can be used to obtain endogenous expression levels of tagged proteins . This approach provides consistent detection across strain backgrounds while maintaining physiological relevance.

What considerations are important when interpreting BUD9 antibody data in phenotypic studies?

When using BUD9 antibodies for phenotypic studies, researchers should consider several important factors for accurate data interpretation:

Expression level variations:

• Bud9p expression varies naturally during the cell cycle, with peak expression in G1 phase

• Quantify relative expression levels when comparing different conditions

• Correlate protein levels with observed phenotypes

• Consider using constitutive promoters (e.g., MET25) to standardize expression for certain experiments

Localization versus function correlation:

• Bud9p concentration at the distal pole doesn't always correlate directly with function

• Bud9p acts as a negative regulator of distal budding despite being concentrated at the distal pole

• Consider post-translational modifications or conformational changes that might activate/inactivate the protein

• Validate functional relevance of localization changes with budding pattern analysis

Tag interference considerations:

• Different tags (myc, GFP) may subtly affect Bud9p localization patterns

• Compare results obtained with different tagging approaches

• Validate key findings using antibodies against the native protein when possible

• Perform phenotypic complementation tests to confirm functionality of tagged proteins

Strain background effects:

• Budding patterns vary between haploid and diploid strains despite identical Bud9p localization

• Additional factors may override or modify Bud9p function in different genetic backgrounds

• Include appropriate wild-type controls matched to the strain background

• Consider epistasis analysis to place Bud9p in the context of strain-specific pathways

Environmental condition interactions:

• Nitrogen starvation affects Bud9p localization and function

• Document all experimental conditions precisely

• Consider how media composition and growth conditions might affect results

• Test key findings across multiple environmental conditions

Research has shown that PH cells display a unipolar distal pattern much like YF bud9 mutant cells, suggesting that nitrogen starvation might naturally replicate the artificial situation created by deletion of BUD9 . This highlights the importance of considering environmental factors when interpreting BUD9 antibody data in phenotypic studies.