SPATA22 Antibody

What is SPATA22 and what are its critical functions in meiosis?

SPATA22 (Spermatogenesis Associated 22) is a vertebrate-specific protein that plays an essential role in meiotic recombination. It is predominantly expressed in the germ cells of both sexes and is crucial for meiotic progression . SPATA22 forms an obligate complex with MEIOB, and together they share structural features and interaction patterns with Replication Protein A (RPA) .

The protein has two well-conserved domains: an N-terminal segment with no predicted structure and a C-terminal region (amino acids 228-341) that contains an OB (Oligonucleotide/oligosaccharide Binding) fold domain. This C-terminal domain is essential for SPATA22's interaction with MEIOB .

Functionally, SPATA22 is required for:

• Proper processing of meiotic recombination intermediates

• Maintaining homologous recombination (HR) foci

• Supporting the synapsis of homologous chromosomes

• Ensuring the repair of meiotic DNA double-strand breaks

Mutants lacking functional SPATA22 show arrest at early meiotic prophase, with subsequent germ cell loss in both males and females, leading to complete infertility .

What are the validated applications for SPATA22 antibodies in research?

SPATA22 antibodies have been successfully validated for several research applications:

When performing immunolocalization of SPATA22, researchers have successfully used paraformaldehyde-fixed tissue sections (4%) incubated with primary antibodies diluted in ADB (Antibody Dilution Buffer), followed by appropriate secondary antibodies tagged with fluorophores like Alexa Fluor 488 or 594 .

How should researchers validate SPATA22 antibody specificity?

Validating SPATA22 antibody specificity is critical for reliable experimental results. A comprehensive validation approach includes:

• Positive controls: Always include testis tissue from wild-type animals, where SPATA22 is highly expressed .

• Negative controls:

  • Use testis samples from SPATA22 knockout mice (Spata22-/- or equivalent mutants)

  • Include no-primary-antibody controls in immunostaining procedures

  • Test reactivity in tissues known not to express SPATA22

• Western blot validation: Confirm a single band at the expected molecular weight of approximately 41 kDa .

• Blocking peptide competition: Pre-incubate the antibody with the immunizing peptide to demonstrate specific binding.

• Recombinant protein expression: Compare staining patterns between cells transfected with SPATA22 and non-transfected cells.

• RNA interference: Correlate antibody signal reduction with SPATA22 knockdown.

Researchers should note that while Spata22 transcript may still be detected in mutant mice (as seen in the Spata22shani/shani mutants), SPATA22 protein may be absent, making such models useful negative controls .

What is the optimal protocol for immunolocalization of SPATA22 in testicular sections?

Based on published methodologies, the following protocol is recommended for optimal immunolocalization of SPATA22 in testicular sections:

• Tissue fixation and preparation:

  • Fix testes by immersion in 4% paraformaldehyde

  • Process and embed tissues according to standard protocols

  • Section tissues at 5-7 μm thickness

• Antigen retrieval:

  • Preferred method: Heat-induced epitope retrieval with TE buffer pH 9.0

  • Alternative method: Citrate buffer pH 6.0

• Blocking and primary antibody incubation:

  • Block with 10% ADB (Antibody Dilution Buffer)

  • Incubate sections with SPATA22 antibody diluted 1:10 to 1:500 in ADB

  • Include a negative control well with only ADB (no primary antibody)

• Secondary antibody and visualization:

  • Incubate with 1:1000 dilution of appropriate secondary antibody (e.g., Alexa Fluor 488 or 594)

  • Incubate for 1-2 hours in a humidified dark chamber

  • Perform washing steps, including one wash supplemented with DAPI (4′,6-diamidino-2-phenylindole)

  • Mount with Prolong Antifade or similar mounting medium

• Imaging:

  • Image using fluorescence microscopy

  • For colocalization studies, use appropriate filter sets for multiple fluorophores

This protocol has been successfully used to visualize SPATA22 in seminiferous tubules and to study its colocalization with other meiotic proteins .

How can researchers effectively study SPATA22-MEIOB protein interactions?

Studying the SPATA22-MEIOB interaction requires specialized techniques given their obligate complex formation. Based on published methodologies:

• Co-immunoprecipitation (Co-IP):

  • Prepare testis lysates with strong nuclease treatment to avoid aberrant interactions due to oligonucleotide bridges

  • Use antibodies directed against tags if working with tagged proteins, or use specific antibodies against SPATA22 and MEIOB

  • Include appropriate controls to confirm specific interactions

• Protein co-expression systems:

  • Co-express SPATA22 and MEIOB in insect cells for copurification

  • Note that purifying SPATA22 or MEIOB individually has proven challenging; success has been achieved through GST-pull down after their coexpression

• Domain interaction analysis:

  • Create truncated versions of SPATA22 and MEIOB lacking C-terminal OB-fold containing domains

  • The C-terminal OBCD of SPATA22 (SPATA22 OBCD) and OBCD3 of MEIOB are required and sufficient for their interaction

• Biochemical assays with purified proteins:

  • After co-purification, use electrophoretic mobility shift assays to study their binding to ssDNA

  • Perform immunoblot analyses to verify the presence of both proteins in shifted complexes

Research has shown that MEIOB and SPATA22 form a complex that can bind ssDNA, and when added to RPA-coated ssDNA, they form a higher-order complex where all components coexist on the DNA .

What techniques are recommended for visualizing SPATA22-RPA interactions in meiotic cells?

Studying SPATA22-RPA interactions in meiotic cells requires specialized approaches:

• Chromosome spreading technique:

  • Prepare chromosome spreads from testicular cells following established protocols

  • Perform dual immunofluorescence staining for SPATA22 and RPA subunits (RPA1, RPA2, or RPA3)

  • Analyze colocalization of SPATA22 and RPA foci on chromosome axes

• Quantitative foci analysis:

  • Count and measure the intensity of SPATA22 and RPA foci

  • Analyze correlation between RPA1 and RPA2 foci intensities in wild-type versus Meiob-/- backgrounds

  • Note that in wild-type cells, RPA1 and RPA2 foci intensities do not correlate, whereas in Meiob-/- cells, they do correlate (similar to somatic cells)

• Super-resolution microscopy:

  • Use techniques like structured illumination microscopy (SIM) or stochastic optical reconstruction microscopy (STORM) to better resolve the spatial organization of SPATA22-RPA complexes on meiotic chromosomes

• Proximity ligation assay (PLA):

  • Apply PLA to detect close proximity (<40 nm) between SPATA22 and RPA proteins in situ

  • This method provides higher specificity for detecting true protein-protein interactions in fixed cells

Research has shown that SPATA22 and MEIOB cooperate to interact with endogenous RPA, and their minimum dimerization core (C-terminal OBCDs) is sufficient for this interaction .

What are the functional consequences of SPATA22 deficiency in meiotic cells?

SPATA22 deficiency leads to several well-characterized defects in meiotic cells:

• Arrest at early meiotic prophase:

  • Spermatocytes and oocytes arrest at a zygotene-like stage

  • No post-meiotic germ cells are produced

• Defects in homologous recombination:

  • Initial formation of Rad51 foci is normal, but their maintenance is impaired

  • Rad51 foci numbers decline from the leptotene-like stage in Spata22-deficient cells

  • DSB repair is impaired, leading to accumulation of recombination intermediates

• Defective chromosome synapsis:

  • Homologous chromosomes fail to achieve normal synapsis

  • The synaptonemal complex does not form properly

• BLM helicase accumulation:

  • In the absence of MEIOB (which partners with SPATA22), the BLM helicase accumulates on RPA-associated HR intermediates

  • This accumulation occurs simultaneously with DMC1 recombinase dissociation

  • These observations suggest that SPATA22-MEIOB is essential for proper processing of ssDNA-containing HR intermediates

• Cellular consequences:

  • Increased apoptosis of spermatocytes

  • Reduced gonad size (hypogonadism)

  • Complete infertility in both males and females

These phenotypes highlight SPATA22's essential role in meiotic recombination, particularly in ensuring proper processing of DNA intermediates during homologous recombination.

What are key considerations when using SPATA22 antibodies in Western blot analysis?

When using SPATA22 antibodies for Western blot analysis, researchers should consider:

• Expected molecular weight:

  • SPATA22 should be detected at approximately 41 kDa

  • The calculated molecular weight based on amino acid sequence is 41 kDa (363 amino acids)

• Sample preparation:

  • Use testis tissue as positive control (human or mouse)

  • Include fresh protease inhibitors in lysis buffers

  • For optimal results, prepare fresh samples or store at -80°C in aliquots to avoid freeze-thaw cycles

• Antibody dilution range:

  • Optimal dilutions range from 1:500 to 1:2000

  • Titrate the antibody for your specific experimental system

• Blocking conditions:

  • 5% non-fat dry milk or BSA in TBST is typically effective

  • For phospho-specific antibodies, BSA is preferred over milk

• Controls to include:

  • Positive control: Wild-type testis lysate

  • Negative control: Spata22 knockout/mutant testis lysate

  • Molecular weight marker

• Detection method:

  • Both chemiluminescence and fluorescence-based detection systems work well

  • For quantitative analysis, fluorescence-based systems offer better linearity

• Troubleshooting considerations:

  • If multiple bands appear, optimize primary antibody concentration

  • For weak signals, increase protein load or primary antibody concentration

  • For high background, increase blocking time or washing steps

Following these guidelines will help ensure specific and reproducible detection of SPATA22 protein in Western blot analyses.

How can researchers perform quantitative analysis of SPATA22 foci in meiotic chromosome spreads?

Quantitative analysis of SPATA22 foci in meiotic chromosome spreads requires careful methodology:

• Preparation of chromosome spreads:

  • Use fresh testicular tissue processed according to established protocols

  • Create consistent spreading conditions to ensure reproducibility

• Immunostaining protocol:

  • Use validated SPATA22 antibody at optimized dilution (typically 1:100-1:200)

  • For co-staining, include antibodies against synaptonemal complex proteins (e.g., SYCP3) as axis markers

  • Include stage-specific markers to accurately identify prophase I substages

• Image acquisition:

  • Use consistent exposure settings across all samples

  • Capture z-stacks to ensure all foci are detected

  • Use high-resolution microscopy (confocal or structured illumination)

• Quantification methodology:

  • Count total number of SPATA22 foci per nucleus

  • Measure foci intensity using appropriate software (ImageJ/Fiji, CellProfiler)

  • Analyze colocalization with other proteins of interest (RPA, DMC1, RAD51)

• Stage-specific analysis:

  • Categorize cells by meiotic prophase stage (leptotene, zygotene, pachytene)

  • Compare foci numbers and distributions across stages

  • Note that SPATA22 foci patterns vary with meiotic progression

• Statistical analysis:

  • Use appropriate statistical tests (t-test for two groups, ANOVA for multiple groups)

  • Present data as mean ± SD or SEM with individual data points

  • For correlation analysis of foci intensities (e.g., SPATA22 vs. RPA), use Pearson's correlation coefficient

This approach has been used to characterize how SPATA22 interacts with other recombination proteins and how its distribution changes during meiotic progression .

What is the recommended protocol for assessing SPATA22-ssDNA interactions in vitro?

Based on published methodologies, researchers can assess SPATA22-ssDNA interactions using:

• ssDNA pulldown assay:

  • Express human SPATA22 (co-express with MEIOB) using TnT T7 Quick Coupled Transcription/Translation System

  • Prepare biotinylated ssDNA and dsDNA

  • Perform binding reactions in buffer containing: 25 mM Tris-HCl (pH 7.5), 100 mM NaCl, 1 mM EDTA, 5 mg/ml BSA, 0.05% Tween 20, 10% glycerol, 1 mM β-mercaptoethanol, and protease inhibitors

  • Use Dynabeads M-280 Streptavidin for pulldown

  • Wash with rinsing buffer (25 mM Tris-HCl, pH 7.5, 150 mM NaCl, 1 mM EDTA, 0.05% Tween 20, 10% glycerol, 1 mM β-mercaptoethanol, protease inhibitors)

  • Elute in Laemmli buffer and analyze by Western blot

• Electrophoretic mobility shift assay (EMSA):

  • Use purified MEIOB-SPATA22 complex (note: individual proteins are difficult to purify)

  • Prepare Cy5-labeled ssDNA oligonucleotide (e.g., 46-mer)

  • Pre-incubate ssDNA with or without RPA

  • Add increasing amounts of MEIOB-SPATA22 complex

  • Analyze on non-denaturing acrylamide gels

  • For protein detection, transfer to membrane and immunostain for MEIOB, SPATA22, and RPA subunits

• Transmission electron microscopy (TEM):

  • Prepare RPA-coated circular ssDNA with or without MEIOB-SPATA22

  • Apply to carbon-coated grids and stain with uranyl acetate

  • Observe under TEM to visualize nucleoprotein complexes

  • Measure contour length and thickness of protein-coated ssDNA

  • This approach has revealed that MEIOB-SPATA22 causes RPA-coated ssDNA to become thicker with decreased contour length

These methods have demonstrated that MEIOB-SPATA22 can bind ssDNA directly and also interacts with RPA-coated ssDNA to change its conformation, providing insights into its role in meiotic recombination.

What factors affect SPATA22 antibody performance in immunofluorescence experiments?

Several critical factors influence SPATA22 antibody performance in immunofluorescence:

• Fixation method and duration:

  • 4% paraformaldehyde is the validated fixation method for SPATA22 detection

  • Overfixation can mask epitopes and reduce signal intensity

  • Underfixation may compromise tissue morphology and protein retention

• Antigen retrieval technique:

  • Heat-induced epitope retrieval with TE buffer pH 9.0 is recommended

  • Alternative: citrate buffer pH 6.0

  • Optimization of retrieval time is crucial for specific detection

• Blocking parameters:

  • Insufficient blocking leads to high background

  • Excessive blocking may reduce specific signal

  • Optimize blocking agent (BSA, serum, commercial blockers) and duration

• Primary antibody characteristics:

  • Polyclonal antibodies may provide higher sensitivity but lower specificity

  • Clone selection for monoclonal antibodies is critical

  • Antibody concentration must be carefully titrated for each application

• Tissue-specific considerations:

  • SPATA22 expression is predominantly in testis tissue

  • Stage-specific expression during spermatogenesis affects detection

  • Background autofluorescence in testis tissue requires appropriate controls

• Antibody validation status:

  • Use antibodies validated specifically for immunofluorescence applications

  • Check published literature for successful application references

  • Consider multiple antibodies targeting different epitopes for confirmation

• Storage and handling:

  • Aliquot antibodies to avoid freeze-thaw cycles

  • Store at -20°C for optimal stability

  • Follow manufacturer's recommendations for long-term storage

Addressing these factors systematically will help researchers optimize SPATA22 detection in immunofluorescence experiments.

How should researchers approach troubleshooting when SPATA22 antibodies fail to detect the protein?

When SPATA22 antibodies fail to detect the target protein, follow this systematic troubleshooting approach:

• Verify expression in your experimental system:

  • Confirm SPATA22 expression in your tissue/cell type using RT-PCR

  • Consider developmental timing, as SPATA22 expression is stage-specific during spermatogenesis

  • Check for mutation or splice variants that might affect antibody recognition site

• Antibody validation:

  • Test antibody on positive control (wild-type testis tissue)

  • Verify antibody functionality using Western blot before immunostaining

  • Consider alternative antibodies targeting different epitopes

• Protocol optimization:

  • Fixation: Test different fixation methods and durations

  • Antigen retrieval: Compare heat-induced vs. enzymatic methods

  • Antibody concentration: Titrate antibody using a wider range of dilutions

  • Incubation time/temperature: Test overnight at 4°C vs. room temperature incubation

• Technical considerations:

  • Sample handling: Ensure tissues are fresh and properly processed

  • Detection system: Try more sensitive detection methods

  • Blocking reagents: Test alternative blocking agents to reduce background

  • Secondary antibody compatibility: Ensure compatibility with primary antibody host species

• Potential biological explanations:

  • Protein degradation: Add protease inhibitors throughout sample preparation

  • Post-translational modifications: Consider if modifications might mask epitopes

  • Protein interactions: Detergent conditions may need adjustment to expose epitopes in protein complexes

  • Low abundance: Consider signal amplification systems

• Alternative detection approaches:

  • Try epitope tag systems if studying exogenous SPATA22

  • Consider RNA in situ hybridization to confirm expression pattern

  • Use mass spectrometry for protein identification and validation

Document all troubleshooting steps systematically to build an optimized protocol for your specific experimental system.

Human, Mouse, Polyclonal, Proteintech 20 μL

What are the best approaches for studying SPATA22 mutant phenotypes in reproductive research?

When studying SPATA22 mutant phenotypes in reproductive research, consider these methodological approaches:

The shani mouse model provides a valuable tool for such studies, as it carries a point mutation in Spata22 that affects splicing, leading to reduced SPATA22 protein levels and meiotic defects similar to those in null mutants .

How can researchers distinguish between direct and indirect effects of SPATA22 deficiency?

Distinguishing between direct and indirect effects of SPATA22 deficiency requires sophisticated experimental approaches:

• Temporal analysis of phenotype development:

  • Create or use inducible knockout systems to control the timing of SPATA22 depletion

  • Track the sequence of events following SPATA22 loss to identify primary vs. secondary effects

  • Compare early vs. late phenotypic changes in mutants

• Structure-function analysis:

  • Generate truncation mutants targeting specific domains of SPATA22

  • Create point mutations in key residues of the OB-fold domain

  • Test the ability of mutant constructs to rescue SPATA22-deficient phenotypes

• Protein-protein interaction mapping:

  • Perform immunoprecipitation followed by mass spectrometry to identify SPATA22 interactors

  • Validate direct interactions using yeast two-hybrid or in vitro binding assays

  • Conduct proximity ligation assays to confirm interactions in situ

  • Map interaction domains using truncated proteins

• Biochemical activity assays:

  • Test the effect of purified SPATA22-MEIOB complex on RPA-ssDNA interactions

  • Analyze DNA binding properties using electrophoretic mobility shift assays

  • Examine the effect on recombination intermediates in cell-free systems

• Genetic complementation strategies:

  • Express wild-type SPATA22 in mutant backgrounds to confirm direct causality

  • Perform domain-specific rescue experiments to identify critical functional regions

  • Use heterologous expression systems to test conservation of function across species

• Comparative analysis of phenotypes:

  • Compare SPATA22-deficient phenotypes with those of interacting partners (MEIOB, RPA)

  • Identify shared vs. unique phenotypic features to infer functional relationships

  • Create and analyze double mutants to test genetic interactions

These approaches have revealed that SPATA22 and MEIOB form an obligate complex that modifies properties of RPA-coated ssDNA to facilitate meiotic recombination .

What considerations are important when selecting between polyclonal and monoclonal SPATA22 antibodies?

When choosing between polyclonal and monoclonal SPATA22 antibodies, consider:

Application-specific recommendations:

• For Western blot:

  • Both polyclonal (1:500-1:2000) and monoclonal (1:2000) antibodies work well

  • Polyclonals may detect multiple isoforms or post-translational modifications

  • Monoclonals provide higher specificity for a particular form

• For immunohistochemistry:

  • Polyclonals (1:50-1:500) often provide stronger signal in fixed tissues

  • Monoclonals (1:150) may require more optimization but give cleaner results

• For co-immunoprecipitation:

  • Polyclonals are advantageous for pulling down protein complexes

  • Multiple epitope recognition increases capture efficiency

• For quantitative analysis:

  • Monoclonals provide more consistent results for comparative studies

  • Better for reproducible quantification across experiments