FOXD4/FOXD4L4/FOXD4L5/FOXD4L2/FOXD4L3/FOXD4L6/ Antibody

What are FOXD4 and its related proteins?

FOXD4 (Forkhead box protein D4) and its related proteins (FOXD4L2, FOXD4L3, FOXD4L4, FOXD4L5, and FOXD4L6) are members of the forkhead/winged helix-box (FOX) family of transcription factors. These proteins contain a conserved fork head DNA-binding domain and play critical roles in the regulation of multiple processes including metabolism, cell proliferation, and gene expression during ontogenesis . FOXD4 has several synonyms including FKHL9, FOXD4A, FREAC5, Forkhead-related protein FKHL9, Forkhead-related transcription factor 5, FREAC-5, and Myeloid factor-alpha .

What is the molecular weight of FOXD4 and related proteins?

Where are FOXD4 family proteins localized in cells?

FOXD4 and its related proteins are nuclear proteins . This localization is consistent with their function as transcription factors that bind to DNA and regulate gene expression. When performing immunocytochemistry or immunofluorescence experiments, researchers should expect nuclear staining patterns.

What types of antibodies are available for FOXD4 family proteins?

Both polyclonal and monoclonal antibodies targeting FOXD4 family proteins are commercially available. Polyclonal antibodies like Proteintech's 24835-1-AP (anti-FOXD4) and 22081-1-AP (anti-FOXD4L6) are rabbit-derived. Monoclonal antibodies such as YP-mAb-01722 (anti-FoxD4/D4L) are mouse-derived . The selection between polyclonal and monoclonal depends on your specific experimental requirements, with polyclonals offering broader epitope recognition but potentially higher background, while monoclonals provide higher specificity.

How do I validate a FOXD4 family antibody for my research?

Validation of FOXD4 family antibodies should include:

• Western blot analysis: Using positive control samples like NIH/3T3, Jurkat, RAW 264.7, or U-937 cells for FOXD4 , or A431, HepG2, or Jurkat cells for FOXD4L6 .

• Correct molecular weight identification: Expect bands at approximately 65-70 kDa rather than the calculated 46-47 kDa .

• Knock-down controls: Using siRNA against your target to demonstrate specificity.

• Peptide competition assay: Using blocking peptides like FOXD4L3 Antibody (N-term) Blocking Peptide to confirm specificity.

• Cross-reactivity testing: Evaluate reactivity across species (human, mouse, rat) as indicated in product information .

Which epitope regions of FOXD4 family proteins are commonly targeted by antibodies?

Commercial antibodies typically target diverse regions of FOXD4 family proteins. For example:

• YP-mAb-01722 targets amino acids 281-330 of human FOXD4/L2/L3/L4/L5/L6

• Some antibodies are raised against recombinant fusion proteins of the entire or significant portions of the protein

• N-terminal targeting antibodies are also available

For research focused on specific FOXD4 variants, selecting antibodies that target unique regions not shared among family members is crucial to ensure specificity.

What are the recommended dilutions for FOXD4 family antibodies in different applications?

It is recommended to optimize these dilutions for your specific experimental conditions and sample types.

What is the optimal protocol for western blot detection of FOXD4 proteins?

For optimal western blot detection of FOXD4 family proteins:

• Sample preparation:

  • Use nuclear extracts as FOXD4 proteins are nuclear localized

  • Include protease inhibitors to prevent degradation

  • Positive controls: NIH/3T3, Jurkat, RAW 264.7, or U-937 cells for FOXD4 ; A431, HepG2, Jurkat cells for FOXD4L6

• Gel electrophoresis and transfer:

  • Use 8-10% SDS-PAGE to achieve good separation in the 60-70 kDa range

  • Ensure complete transfer of higher molecular weight proteins

• Blocking and antibody incubation:

  • Block with 5% non-fat milk in TBST

  • Primary antibody incubation: Use dilutions of 1:500-1:2000

  • Overnight incubation at 4°C generally yields best results

• Detection considerations:

  • Expect bands at 65-70 kDa rather than the calculated 46-47 kDa

  • Include molecular weight markers that cover 40-80 kDa range

How can I optimize immunofluorescence staining for FOXD4 family proteins?

For immunofluorescence detection of nuclear-localized FOXD4 family proteins:

• Fixation and permeabilization:

  • PFA fixation (4%) for 15 minutes at room temperature

  • Triton X-100 (0.2-0.5%) permeabilization is crucial for nuclear protein access

  • FOXP4 antibody testing has demonstrated successful staining using these conditions

• Blocking and antibody incubation:

  • Use 5-10% normal serum (matching secondary antibody host) with 0.1% Triton X-100

  • Incubate primary antibody overnight at 4°C

  • Use a starting dilution of 1:100-1:200, then optimize

• Counterstaining:

  • Include DAPI or Hoechst for nuclear counterstaining to confirm nuclear localization

  • Consider co-staining with other nuclear markers or cell type-specific markers

• Controls:

  • Include negative controls (primary antibody omission)

  • If possible, include FOXD4-knockout or knockdown samples

How can FOXD4 antibodies be used to study neural development and differentiation?

FOXD4 plays critical roles in neural development, particularly in establishing neural cell fate and neuronal differentiation . To study these processes:

• Developmental time-course studies: Use anti-FOXD4 antibodies to track expression during neural plate formation and neurogenesis in tissue sections or embryoid bodies.

• Embryonic stem cell differentiation models: FOXD4 is essential for the transition from pluripotent embryonic stem cells to neuroectodermal stem cells . Use western blotting and immunofluorescence to monitor FOXD4 expression during differentiation protocols.

• Co-immunoprecipitation studies: FOXD4 interacts with the Groucho co-repressor at the Eh-1 motif . Use anti-FOXD4 antibodies for co-IP to identify interaction partners in neural precursors.

• ChIP-seq applications: Use ChIP-grade FOXD4 antibodies to identify genomic binding sites and regulatory targets in neural precursors, which could include genes like sox2, sox3, sox11, zic1, zic2, zic3, and irx family members .

What roles do FOXD4 family proteins play in cancer, and how can antibodies help investigate these roles?

FOXD4 has been implicated in cancer progression, particularly in colorectal cancer (CRC) . Research strategies include:

• Expression analysis in clinical samples: Use immunohistochemistry with anti-FOXD4 antibodies to compare expression between normal tissues and tumors, correlating with clinical outcomes.

• Mechanistic studies: FOXD4 has been shown to affect metastasis by inducing epithelial-mesenchymal transition (EMT) through direct binding to the SNAI3 promoter . Use ChIP assays with FOXD4 antibodies to confirm binding to promoters of EMT-related genes.

• Functional validation: After FOXD4 knockdown or overexpression in cancer cell lines, use western blot analysis to confirm altered protein levels and to examine downstream effectors.

• Subcellular localization studies: Cytoplasmic localization or down-regulation of FOX proteins via AKT, IKK, and ERK-mediated phosphorylation has been observed in some cancers . Use immunofluorescence to determine FOXD4 localization in cancer cells.

How do I troubleshoot cross-reactivity issues between FOXD4 family members when using antibodies?

The high sequence similarity between FOXD4 and its related proteins (FOXD4L2-L6) presents challenges for antibody specificity. To address cross-reactivity:

• Epitope mapping: Choose antibodies targeting unique regions not conserved across family members. The immunogen information provided with antibodies can help determine potential cross-reactivity .

• Knockout validation: Use CRISPR/Cas9 to knock out specific FOXD4 family members and test antibody specificity against these controls.

• Peptide competition: Use specific blocking peptides for individual family members to determine which signals are attributable to which protein .

• Expression pattern analysis: Different FOXD4 family members may have distinct tissue expression patterns. Compare antibody signals with known expression data from RNA-seq or other sources.

• Western blot analysis: Look for subtle molecular weight differences between family members to distinguish signals.

Why does FOXD4 often appear at a higher molecular weight than predicted in western blots?

The discrepancy between calculated (46-47 kDa) and observed (60-70 kDa) molecular weights may be due to:

• Post-translational modifications: Phosphorylation, SUMOylation, or other modifications can significantly alter protein migration.

• Protein structure: The fork head DNA-binding domain may affect migration behavior in SDS-PAGE.

• High isoelectric point: FOXD4 proteins may bind less SDS due to their charge properties.

To confirm identity despite the molecular weight discrepancy:

• Use multiple antibodies targeting different epitopes

• Include recombinant protein standards

• Perform peptide competition assays

• Validate with knockdown or knockout controls

How can researchers distinguish between FOXD4 and other FOX family members in their experiments?

The FOX family includes numerous members (FOXA-FOXS) with similar DNA-binding domains. To ensure specificity for FOXD4:

• Antibody selection: Choose antibodies that target regions outside the conserved fork head domain.

• Bioinformatic analysis: Compare target sequences between FOX family members to identify unique peptide regions.

• Multiple detection methods: Combine western blots with qPCR or RNA-seq to confirm that protein detection correlates with mRNA expression.

• Functional validation: FOXD4's roles in neural development and cancer progression can be used to validate identity through functional assays.

• Co-expression analysis: FOXD4 has specific interaction partners like Groucho/Grg4 ; co-immunoprecipitation can help validate identity.

What considerations should be made when using FOXD4 antibodies for studying protein-protein interactions?

When investigating FOXD4 protein interactions:

• Antibody binding sites: Ensure the antibody's epitope doesn't overlap with interaction domains. FOXD4 interacts with Groucho/Grg4 at the Eh-1 motif in the C-terminus , so antibodies targeting this region may interfere with binding.

• Buffer conditions: For co-immunoprecipitation, use buffers that maintain native protein conformations while effectively extracting nuclear proteins:

  • TNSG lysis buffer has been successful for FOXD4-Groucho interactions

  • Include DNase treatment to release DNA-bound transcription factors

• Crosslinking considerations: For transient interactions, consider using crosslinking agents before immunoprecipitation.

• Controls: Include IgG controls, input samples, and when possible, interaction-deficient mutants (e.g., FOXD4 with mutated Eh-1 motif ).

• Validation: Confirm interactions using reciprocal co-IPs and alternative methods like proximity ligation assay or FRET.